JPH06167554A - Reflection type magneto-optical sensor head - Google Patents

Abstract

(57) [Summary] [Purpose] Using a bismuth-substituted magnetic garnet film,
(EN) Provided is a reflection type optical magnetic field sensor which is compact, lightweight and can be mass-produced at a low price. [Constitution] In a reflection type optical magnetic field sensor head in which an optical input / output path, a polarizer, a Faraday rotator and a reflective film are arranged in this order, the [111] axis is the Faraday rotator with respect to the film normal
(111) Bismuth-substituted magnetic garnet single crystal film tilted within the range of 1 to 60 degrees and (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis is substantially aligned with the film normal. We adopted a Faraday rotator formed of multiple (111) bismuth-substituted magnetic garnet single crystals with. [Effect] The presence or absence of a magnetic field in a very narrow space can be detected and detected easily and with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical magnetic field sensor head utilizing the Faraday effect of a bismuth-substituted magnetic garnet film. More specifically, the present invention relates to an improvement of a reflection type optical magnetic field sensor head for detecting the strength of a magnetic field which is small and lightweight and can be easily mass-produced in a magnetic field sensor for detecting the strength of a magnetic field. .

[0002]

2. Description of the Related Art At present, many general-purpose industrial equipments and consumer equipments have rotating devices such as motors and gears and rotating parts. Due to advances in science and technology, global environment protection, and increasing social concern and demand for energy conservation, operation control of industrial equipment, such as aircraft and ships, and consumer equipment, such as rotating equipment and devices such as passenger cars. Attempts have been made to implement this with higher accuracy and precision.

In order to realize more sophisticated and highly accurate operation control of rotating machines and devices as one of the concrete methods for responding to social demands for protection of the global environment and energy saving, first of all, accurate rotation is required. Speed [number] continuously,
Moreover, it must be possible to know immediately. In order to know the accurate rotation speed (number) of the rotating equipment / device, a highly reliable tachometer / measuring device capable of instantaneously measuring the accurate rotation speed must be provided. However, it can still respond to this social demand, and more specifically, it is small and lightweight, has high precision, is easy to handle, and can withstand long-term continuous use in a harsh environment accompanied by high temperature and vibration. There is no measuring device that can be manufactured and is inexpensive. In order to respond to international social demands for global environmental protection and energy saving, it is necessary to develop measuring devices with high performance that can respond to social demands promptly and to provide them at low cost and in large quantities. There is.

As a method for measuring the rotational speed [number], a method utilizing electromagnetic induction [sensor technology, 1986, 12
Issue, p. 68] and a method using an optical magnetic field sensor that utilizes the Faraday effect of magneto-optical materials [Applied Optics, Vol. 28, No. 11, p. 1992 (1
989)] has been proposed.

The method utilizing electromagnetic induction has already been used for measuring and measuring the rotational speed [number] of aircraft and automobile engines. However, the tachometer using electromagnetic induction has a serious drawback that it is inferior in reliability because it is susceptible to electromagnetic noise in the transmission line [cable] between the measurement terminal and the device body. Also, because an electric circuit is used, facilities that handle flammable substances such as organic solvents, that is, hazardous materials,
In other words, there is a serious problem that hazardous materials factories and hazardous material handling sites must implement explosion-proof measures.

In the method using the optical magnetic field sensor utilizing the Faraday effect of the magneto-optical material, when the permanent magnet [magnetic field] approaches the optical magnetic field sensor, the polarization plane of the magneto-optical material in the optical magnetic field sensor is changed to the magnetic field [magnet]. It is used to rotate depending on the presence or absence of. That is, the rotation speed [number] is to be measured by converting the rotation of the polarization plane of the light passing through the magneto-optical material in the optical magnetic field sensor into a change in the light intensity to detect and count the rotation [number]. Report (N
ational Technical Report), Vol.29, No.5, P70 (1983)
].

The optical magnetic field sensor is classified into a transmission type and a reflection type. Due to the nature of its components, the transmissive type is arranged so that the incident and transmitted directions of signal light are aligned.
Since they must be arranged, there is a restriction on the installation location, and depending on the purpose of use and the installation location, they cannot be installed or adopted.

A reflection type optical magnetic field sensor has been proposed as a structure for improving the drawbacks of the transmission type optical magnetic field sensor.
56-55811, Japanese Examined Patent Publication 3-22595]. In the reflection type optical magnetic field sensor proposed here, the input optical fiber and the output optical fiber of the signal light are on the same side with respect to the Faraday rotator, in other words, the output optical fiber is the input optical fiber. In the same direction as the fiber, in other words, the Faraday rotator is arranged and installed at the tip of the optical magnetic field sensor. Therefore, the reflection type optical magnetic field sensor has a feature that it can be installed in a convoluted and narrow space where the transmission type optical magnetic field sensor cannot be installed due to a small mounting space. But,
The reflection type optical magnetic field sensor proposed by Matsui et al. [Japanese Patent Laid-Open No. 56-55811] requires a lens and a polarizer, and a lens and an analyzer to be arranged in series and in parallel. It remains a serious problem that it is difficult to automate and thus it is difficult to reduce the manufacturing cost.

[0009]

[Problems to be solved by the invention] Matsumura et al.
5] is a method for solving the problem of the reflection type optical magnetic field sensor head proposed by Matsui et al., That is, the problem that it is difficult to automate the assembly work and therefore the manufacturing cost is difficult to reduce. We propose a configuration in which the analyzer and one polarizer are replaced. Matsumura et al. Use yttrium-iron-garnet (chemical structural formula: Y ₃ Fe ₅ O ₁₂ ) as a Faraday rotator (magneto-optical material). Yttrium / iron / garnate is generally called YIG and can be produced by a known method such as a melt method.
Yttrium / Iron / Garnet (YIG) has a characteristic that it has a very high sensitivity as compared with paramagnetic glass and zinc selenide (ZnSe) that have been used as Faraday rotators. Therefore, it can be said that the proposal by Matsumura et al., That is, the use of yttrium-iron-garnet (YIG) as the Faraday rotator of the reflection type optical magnetic field sensor is extremely interesting in terms of its characteristics. However, when considering the properties / characteristics of yttrium / iron / garnet (YIG) with respect to light transmission, the practicality of the magneto-optical sensor as a magneto-optical material, that is, a Faraday rotator, is questioned. That is, yttrium-iron-garnet (YIG) already has the characteristic property that it transmits light in the near-infrared wavelength region with a wavelength of 1.1 μm or more and absorbs light in the 0.8 μm wavelength region well. Because it is known to exist.

At present, generally, as a light source of an optical sensor, a semiconductor laser (LD) or a light emitting diode (LED) having a center wavelength of 0.78 μm to 0.85 μm is widely used for awards. The reason that the semiconductor laser (LD) and the light emitting diode (LED) are widely used as the light source of the optical sensor is that they are already commercially available as a light source device at low cost, and the photodetector has high sensitivity. Therefore, it is most preferable to use a commercially available light source device as the light source of the optical magnetic field sensor. In other words, it is a social issue to provide a commercially available light source device at a low cost to provide a highly sensitive optical magnetic field sensor. It goes without saying that this is the best way to respond to a specific request.

Yttrium / Iron / Garnet (YIG)
The fact that it absorbs light in the 0.8 μm wavelength range well means that
This means that if a commercially available light source device is used as a light source, it may be difficult to detect an optical signal. In other words, yttrium, iron, and garnet (YIG) have fundamental defects and defects in the physical properties and properties required for magneto-optical materials for optical magnetic field sensors, in other words, Faraday rotators. .

The inventors of the present application were strongly interested in the proposal of Matsumura et al. Therefore, the inventors of the present application have conducted various studies on a method of avoiding the drawbacks and fears of yttrium-iron-garnet (YIG), and as a result, the bismuth-substituted magnetic garnet, which has attracted attention as a magneto-optical material, can be I found sex. The bismuth-substituted magnetic garnet proposed here can be relatively easily manufactured by the liquid phase epitaxial (LPE) method and is also excellent in mass productivity. The bismuth-substituted magnetic garnet is represented by the chemical structural formula (RBi) ₃ (FeA) ₅ O ₁₂ . Where R is
Yttrium Y or a rare earth element, where A is
It means aluminum Al or gallium Ga.

The Faraday rotation coefficient of bismuth-substituted magnetic garnet, in other words, the rotation angle of the plane of polarization per unit film thickness when the magnetization is saturated is higher than that of yttrium-iron-garnet (YIG). It is several times or more, more specifically, about 10 times larger at a wavelength of 0.8 μm, for example. Therefore, when the same effect as the magneto-optical material is expected, it is possible to reduce the film thickness of the magneto-optical material in proportion to the Faraday rotation coefficient, and as a result, the absorption loss of light is reduced, It is small and suggests that it can be miniaturized. That is, by changing the material of the magneto-optical material from yttrium / iron / garnet (YIG) to a bismuth-substituted magnetic garnet, the thickness of the device is reduced, the absorption loss of light is reduced, and the light in the wavelength range 0.8 μm band is reduced. It suggests that it is possible to develop an optical magnetic field sensor with a light source.

The saturation magnetic field [500-1200 Oe] of the bismuth-substituted magnetic garnet is about half the saturation magnetic field [about 1800 Oe] of yttrium-iron-garnet (YIG). Therefore, it is expected that a weak magnetic field can be measured. The fact that a weak magnetic field can be measured means that the distance / interval between the permanent magnet and the optical magnetic field sensor can be made longer. This means that the degree of freedom and flexibility of arrangement and installation of the optical magnetic field sensor is improved, which suggests the possibility of expanding the field of application of the optical magnetic field sensor.

The inventors of the present application have obtained the conviction that it is possible to develop a reflective optical magnetic field sensor using a bismuth-substituted magnetic garnet as a magneto-optical material, that is, a Faraday rotator, based on the above-mentioned examination results and the like. In addition, various basic experiments,
And the development experiment was carried out. The present inventors first of all,
Japanese Examined Patent Publication 3-22595 As described in the specification, yttrium
A reflective optical magnetic field sensor [Fig. 1] was manufactured using a bismuth-substituted magnetic garnet instead of iron-garnet (YIG). In FIG. 1, reference numeral 1 is a light source made of a semiconductor laser, reference numeral 2 is a lens, reference numeral 3 is a half mirror that reflects a part of incident light and transmits a part thereof, reference numeral 4 is an optical fiber, and reference numeral 5 is distributed refraction. Lens made of index lens, etc.
6 is a polarizer made of rutile single crystal, etc., 7 is a Faraday rotator made of bismuth-substituted rare earth magnetic garnet,
Reference numeral 8 is a reflective film made of a metal thin film or the like, and reference numeral 9 is a photodetector [power meter]. The signal light emitted from the light source 1 is condensed and guided to the optical fiber 4 via the lens 2 and the half mirror 3. The signal light guided to the optical fiber 4 is collimated by the lens 5 and enters the polarizer 6. The signal light becomes linearly polarized light by the polarizer 6. Then, the linearly polarized signal light is incident on the Faraday rotator 7 and
Part of the light passes through the Faraday rotator and reaches the reflective film 8. The signal light that has reached the reflection film 8 is reflected by the surface of the reflection film 8 and travels backward to enter the Faraday rotator 7 and the polarizer 6 again. Signal light transmitted through the polarizing element 6 (reflected return light)
Are coupled to the optical fiber 4 by the lens 5. The signal light (reflected return light) that has entered the optical fiber 4 enters the half mirror 3. A part of the signal light (reflected return light) incident on the half mirror 3 is reflected by the half mirror 3 and reaches the photodetector 9, and the light intensity thereof is measured.

Next, the inventors of the present invention adopted a bismuth-substituted magnetic garnet as a Faraday rotator, and varied the magnetic field strength applied to the Faraday rotator using the reflective optical magnetic field sensor shown in FIG. Meanwhile, an experiment for detecting an optical signal was performed. However, contrary to the expectations of the inventors of the present application, an optical signal is output regardless of whether or not an external magnetic field is applied.
It could not be detected at all. Therefore, various basic experiments were conducted in order to investigate the reason why the optical signal could not be detected and the cause. As a result, the inventors of the present application, in the reflective optical magnetic field sensor shown in FIG. 1, use a multi-domain structure having a large number of magnetic domains as the Faraday rotation element, regardless of whether an external magnetic field is applied or not. It was concluded that there was no change in strength.

The results of experiments and examinations made by the inventors of the present invention obtained here are based on the fact that yttrium-iron-garnet (YIG), which is the same multi-domain structure as bismuth-substituted magnetic garnet, is used as a Faraday rotation element. The results do not match the experimental results of [Japanese Patent Publication No. 3-22595, Examples]. To the inventors of the present application, a bismuth-substituted magnetic garnet, which is the same multi-domain structure as yttrium / iron / garnet (YIG),
I do not know why it did not work effectively as a Faraday rotator.

The inventors of the present application reexamined the above-mentioned experimental results in detail and conducted more detailed basic experiments. As a result, it was confirmed that the results obtained from the reflective film, the bismuth-substituted magnetic garnet single crystal film, the polarizer, and the optical input / output device. In addition, the light input / output optical path of the optical input / output device is separated into two, and the angle formed by the two optical paths of the separated optical input path and optical output path is set to 5 degrees or more.・ Obtaining the knowledge that a reflective optical magnetic field sensor can be configured by arranging it,
After intensive studies and studies, we have completed and proposed a reflective optical magnetic field sensor using a Faraday rotator made of bismuth-substituted magnetic garnet [Japanese Patent Application No. 4-090976, see FIG. 2].

In FIG. 2, reference numeral 10 is a polarizer such as a polar core [trade name] manufactured by Corning, and reference numeral 11 is a Faraday rotation composed of a bismuth-substituted magnetic garnet single crystal film whose easy axis of magnetization is perpendicular to the film surface. Means a child, to which an external magnetic field is applied. Further, reference numeral 12 is a reflection film made of a dielectric multilayer film, reference numeral 13 is an optical waveguide formed on glass or a polymer film, or an optical input path made of an optical fiber, and reference numeral 14 is a glass. And an optical waveguide formed on a polymer, or an optical output path formed of an optical fiber. In the reflection type optical magnetic field sensor having the configuration shown in FIG. 2, signal light emitted from a light source 16 such as a semiconductor laser is usually guided to a light input path 13 via a lens 15. If desired, the lens 15 installed here may be omitted and the light source 16 and the optical input path 13 may be directly coupled. The signal light incident on the optical input path 13 reaches the sensor head, passes through the polarizer 10 and the Faraday rotator 11, and reaches the reflective film 12. The signal light reaching the reflection film 12 is reflected by the reflection film.
The light is reflected by the surface of 12 and returns, then passes through the Faraday rotator 11 and then the polarizer 10 and enters the optical output path 14, and the photodetector is detected.
Up to 17. The signal light that has reached the photodetector 17 is detected as an optical signal. In the reflection type optical magnetic field sensor having the configuration shown in FIG. 2, the optical input / output optical path of the optical input / output device is divided into two parts, which are configured as an independent optical input path 13 and an independent optical output path 14. Moreover, the input path 13 and the optical output path 14 are arranged and configured such that the angle α formed between them is 5 degrees or more.

The reflection type optical magnetic field sensor using the Faraday rotator made of bismuth-substituted magnetic garnet proposed here is
Currently, it has sufficient performance required for the optical magnetic field sensor in the market. However, the reflective optical magnetic field sensor proposed here requires two optical paths, an optical input path and an optical output path, as shown in FIG. The technical difficulty remains that the optical path must be arranged at an angle of about 5 degrees or more.

Therefore, the inventors of the present invention have keenly made an effort to develop a more versatile, smaller and high performance reflective optical magnetic field sensor by improving the room for technical improvement left here. An improved study was conducted. As a result, a Faraday rotator made of bismuth-substituted magnetic garnet is used as a polarizer, and
Finding that the optical signal can be detected even if the two optical paths, the optical input path and the optical output path, are combined into one by arranging them so as to be inclined with respect to the normal line of the reflection film or the plane. Got Therefore, the inventors of the present application, based on the findings obtained here, further carry out an improved study, the (111) bismuth-substituted magnetic garnet single crystal film, the normal line of the bismuth-substituted magnetic garnet single crystal film, in other words In this case, the magnetization direction and the central axis of the light input / output path, more specifically, the angle between the light traveling direction and the direction of the light, are set within the range of 10 degrees to 70 degrees.
When it was arranged, it was confirmed that the optical paths could be combined into one, and a new reflective optical magnetic field sensor was proposed [Japanese Patent Application No. 4-116141]. However, in the proposed reflection type optical magnetic field sensor [Japanese Patent Application No. 4-116141], it is said that the (111) bismuth-substituted magnetic garnet single crystal film should be installed at a predetermined angle. There are technical difficulties in assembly work and adjustment operation. Next, the inventors of the present application conducted extensive research and experiments to solve technical difficulties in assembly work and adjustment operation, and the [111] axis was in the range of 5 to 60 degrees with respect to the membrane normal. When composed of a bismuth-substituted magnetic garnet single crystal film that tilts inside,
We have found that a high-performance reflective optical magnetic field sensor with a single optical path can be obtained very easily, and have proposed it as a reflective optical magnetic field sensor that is easy to assemble and adjust [Japanese Patent Application No. 4-142929]. However, the reflective optical magnetic field sensor proposed here uses a bismuth-substituted magnetic garnet single crystal film in which the [111] axis, which is expensive as a Faraday rotator, is tilted within the range of 5 to 60 degrees with respect to the film normal. Since it has to be used, it has become clear that it has a new problem that it is inferior in mass productivity and economically disadvantageous. The inventors of the present invention have conducted various experiments to solve the problems left here, and as a result, as a Faraday rotator, a plurality of [111] axes substantially match the film normal. By using a (111) bismuth-substituted magnetic garnet single crystal film, a Faraday rotator is tilted, or a special bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted with respect to the film normal is used. It was confirmed that an optical signal can be detected even if the optical input path and the optical output path are combined into a single optical path without any problem, and a new reflective optical magnetic field sensor was proposed [Japanese Patent Application No. 4-174357]. However, in industrial production, sometimes very rarely, when a Faraday rotator composed of two (111) bismuth-substituted magnetic garnet single crystal films is used, a product that does not function sufficiently as a reflection type optical magnetic field sensor. It has been known that there is a problem that is generated. In other words, the previously proposed reflective optical magnetic field sensor [Japanese Patent Application No. 4-174357] has a possibility of producing a product that does not function sufficiently as a reflective optical magnetic field sensor, in other words, a technical flaw. It became clear that there is. Therefore, in order to guarantee the performance and reliability of the previously proposed reflective optical magnetic field sensor [Japanese Patent Application No. 4-174357], all the products manufactured here shall be tested for their functions and performance. There must be.

[0022]

Means for Solving the Problems The inventors of the present application improved technical defects and defects left in the reflection type optical magnetic field sensor proposed by the inventors of the present application, and immediately measured an accurate rotation speed. It is highly reliable, and more specifically, it is small and lightweight, highly accurate, easy to handle, and can withstand long-term continuous use in harsh environments such as high temperature and vibration. Moreover, by providing an inexpensive tachometer / measuring device, we have earnestly studied and conducted experiments to contribute to the international social demand for global environment protection and energy saving. As a result, first of all, the reason why the previously proposed reflective optical magnetic field sensor [Japanese Patent Application No. 4-174357] is mixed with a product that does not function sufficiently as a reflective optical magnetic field sensor,
We have found that there is a relative optical positional relationship between the optical path and the bismuth-substituted magnetic garnet single crystal film that constitutes the Faraday rotator, that is, it is caused by omitting the optical fine adjustment and alignment operations.

As a practical matter, it is not easy to carry out the optical fine adjustment / alignment operation in the industrial manufacture of the reflection type optical magnetic field sensor. Therefore, the inventors of the present application have conducted earnest study experiments in order to develop a technique that replaces the optical preparation / alignment operation. As a result, as the Faraday rotator, the bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted within the range of 1 to 60 degrees with respect to the film normal and the [111] axis is substantially the film normal. By using a Faraday rotator composed of multiple (111) bismuth-substituted magnetic garnet single-crystal films and (111) bismuth-substituted magnetic garnet single crystal films that are consistent with each other. Based on the finding that the above can be substantially avoided, the inventors of the present invention have completed the present invention by conducting further diligent improvement research, reliability confirmation experiments, and trial production. That is, in the present invention, in the optical magnetic field measurement device in which the optical input / output path, the polarizer, the Faraday rotator, and the reflective film are arranged in this order, the reflective film is
The Faraday rotator is arranged almost perpendicular to the optical path center of the optical input / output path, and the Faraday rotator has a [111] axis tilted within the range of 1 to 60 degrees with respect to the film normal. It is composed of a plurality of (111) bismuth-substituted magnetic garnet single crystal films with a substituted magnetic garnet single-crystal film and a (111) bismuth-substituted magnetic garnet single-crystal film whose [111] axis substantially coincides with the film normal. Reflective optical magnetic field sensor head.

The reflection type optical magnetic field sensor head using the Faraday rotator made of bismuth-substituted magnetic garnet of the present invention has an optical input / output path, a polarizer, and its [111] axis of 1 to 60 degrees with respect to the film normal. Multiple (111) bismuth-substituted magnetic films with bismuth-substituted magnetic garnet single-crystal films tilted within the range and (111) bismuth-substituted magnetic garnet single-crystal films whose [111] axis substantially coincides with the film normal It is composed of a garnet single crystal film and a reflective film [see FIGS. 3 and 4].

The reflection type optical magnetic field sensor head of the present invention comprises:
An optical input / output path, a polarizer, a Faraday rotator composed of a plurality of bismuth-substituted magnetic garnet single crystal films, and a reflective film are arranged in this order from the light source device side (see FIG. 3). That is,
In FIG. 3, reference numeral 18 is a polarizer made of a polar core or the like, reference numeral 19 is a Faraday rotator made of a plurality of bismuth-substituted magnetic garnet single crystal films, and reference numeral 20 is a reflection film made of a metal thin film. Reference numeral 21 denotes an optical input / output path including an optical fiber and an optical waveguide. Here, from the viewpoint of miniaturization of the reflection type optical magnetic field sensor head, the optical input / output path 21 is an optical path for light input, and at the same time, the signal light reflected by the reflection film 20 is incident on the photodetector. It goes without saying that it may have a function of branching to [see FIG. 9].

In a reflection type optical magnetic field sensor using a Faraday rotator made of a bismuth-substituted magnetic garnet single crystal film having a multi-domain structure, an optical signal emitted from an optical input / output path is a lens, a polarizer, and a bismuth-substituted magnetic garnet single crystal film. It passes through the crystal to reach the reflection film, is reflected by the reflection film, is incident on the bismuth-substituted magnetic garnet single crystal again, and is transmitted therethrough. And magnetic domain
It is necessary to pass through b and [Japanese Patent Application No. 4-090976, Japanese Patent Application No. 4-
116141, Japanese Patent Application No. 4-174357, FIGS. 5, 6 and 7].

The previously proposed reflective optical magnetic field sensor [Japanese Patent Application No.
4-174357], sometimes very rarely, a product that does not function sufficiently as a reflection type optical magnetic field sensor is generated because an optical signal emitted from an optical input / output path is caused by an optical positional relationship. , Lens, polarizer, bismuth-substituted magnetic garnet single crystal is transmitted to the reflection film, reflected by the reflection film, again incident on the bismuth-substituted magnetic garnet single crystal, transmitted, to the optical input / output path Between different magnetic domains,
That is, there is a case where the magnetic domains a and b do not pass [see FIG. 7].

[111] axis is substantially coincident with the membrane normal
In the Faraday rotator composed only of the (111) bismuth-substituted magnetic garnet single crystal film, the magnetization direction is parallel to the traveling direction of the signal light, as illustrated in FIG. Therefore, for example, in order that the signal light incident on the magnetic domain a of the first layer passes through different magnetic domains, that is, the magnetic domain b, the second layer or the third layer or later on the straight line of the optical path. Magnetic domain
b must exist. This means that in the Faraday rotator configured as shown in FIG. 7, in order to ensure that the optical signal emitted from the optical input / output path passes through different magnetic domains, that is, magnetic domain a and magnetic domain b, bismuth substitution is performed. It indicates that there is no other method than increasing the number of laminated magnetic garnet single crystals. As a matter of fact, from an economic perspective,
The number of stacked bismuth-substituted magnetic garnet single crystals cannot be increased. Therefore, without increasing the number of stacked bismuth-substituted magnetic garnet single crystals, the optical signal emitted from the optical input / output path is reflected by the reflective film, and before reaching the optical input / output path again, If it is possible to pass different magnetic domains, that is, magnetic domain a and magnetic domain b with higher probability and accuracy, it can be evaluated as an industrial manufacturing technique that replaces the optical fine adjustment / alignment operation.

In the present invention, the Faraday rotator is
11] A bismuth-substituted magnetic garnet single crystal film whose axis is tilted within the range of 1 to 60 degrees with respect to the film normal [111]
By composing with a (111) bismuth-substituted magnetic garnet single crystal film whose axis is substantially coincident with the film normal [see FIG. 4], it is possible to tilt the Faraday rotator or perform a complicated fine adjustment operation. Without doing so, it is possible to obtain the effect of reducing the occurrence rate of defective products that occur in industrial production to below the allowable limit and to substantially zero. That is, in the present invention, an optical signal emitted from an optical input / output path is converted into a bismuth-substituted magnetic garnet single crystal film in which the [111] axis is inclined within a range of 1 to 60 degrees with respect to the film normal. By passing a Faraday rotator composed of a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis substantially coincides with the film normal,
It is intended to pass different magnetic domains, that is, magnetic domain a and magnetic domain b, with higher probability and accuracy. This will be described more specifically with reference to FIG. 3 and FIG.
The optical signal emitted from the optical input / output path 21 indicates that the first bismuth-substituted magnetic garnet single crystal 22 forming the Faraday rotator 19, for example, the [111] axis is substantially aligned with the film normal. Incident on the (111) bismuth-substituted magnetic garnet single crystal film and transmitted through the magnetic domain a, and then the second bismuth-substituted magnetic garnet single crystal 23, for example, the [111] axis is 1 degree to the film normal. The bismuth-substituted magnetic garnet single-crystal film tilted within the range of 60 degrees transmits through the magnetic domain b, and the reflection film 20
While the laser beam is reflected on the second bismuth-substituted magnetic garnet single crystal 23 and reciprocates in the Faraday rotator, the magnetic domains are substantially different from each other with higher probability and accuracy. It passes through a and magnetic domain b.

In practicing the present invention, a Faraday rotator is a bismuth-substituted magnetic material in which the [111] axes of the same or different types are tilted within a range of 1 to 60 degrees with respect to the film normal. It must consist of a garnet single crystal film and a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis is substantially aligned with the film normal. However, the [111] axis is substantially coincident with the film normal with the bismuth-substituted magnetic garnet single crystal film in which the [111] axis is inclined within the range of 1 to 60 degrees with respect to the film normal ( 111) Bismuth-substituted magnetic garnet single-crystal film, other configurations, for example, which one is arranged on the light source side or combination, and (111) Bismuth-substituted magnetic garnet single-crystal film configuration The number of sheets is not particularly limited. Therefore, when carrying out the present invention, the type and composition of the bismuth-substituted magnetic garnet single crystal film that constitutes the Faraday rotator and the number of constituents are
It may be appropriately selected in consideration of the performance and characteristics required for the Faraday rotator.

In the case of an optical magnetic field sensor head which is usually used for general purposes, the same from the practical viewpoint, that is, from the viewpoint of performance / characteristics and material cost of the Faraday rotator,
[111] A bismuth-substituted magnetic garnet single crystal film whose axis is tilted within a range of 1 to 60 degrees with respect to the film normal.
The objective can be sufficiently achieved by using two (111) bismuth-substituted magnetic garnet single crystal films whose axes are substantially coincident with the film normal. In addition, when it has a special purpose, it is preferable to appropriately increase the number of constituents or to select a bismuth-substituted magnetic garnet single crystal having a three-layer structure grown on both surfaces of a non-magnetic garnet substrate.

In carrying out the present invention, the composition of the Faraday rotator, that is, the bismuth-substituted magnetic garnet is not particularly limited, but the general formula: R _3-X Bi _X Fe _5-Z A _Z O ₁₂ [however, , R is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb,
At least one selected from the group of Dy, Ho, Er, Tm, Yb, and Lu, A is at least one selected from the group of Ga, Sc, Al, In, and 0.3 ≤ X ≤ 2.0, 0 ≦ Z ≦
It is preferable to appropriately select from among the magnetic garnet single crystals represented by 1.0].

The (111) bismuth-substituted magnetic garnet single crystal film used in the present invention can be manufactured by a known method. Liquid phase epitaxial (LPE) method [Sin Solid]
Films (Thin Solid Films), Vol.114, p33 (1984)
] Is preferred. When carrying out the liquid phase epitaxial method, any known substrate can be used as the single crystal growth substrate, but generally, the lattice constant which is already commercially available as SGGG substrate is 12.490 Å. , Thru 1
It is preferable to appropriately select from 2.5Å non-magnetic garnet [(GdCa) ₃ (GaMgZr) ₅ O ₁₂ ].

[111] axis is substantially coincident with the membrane normal
The (111) bismuth-substituted magnetic garnet single crystal film is a commercially available non-magnetic garnet substrate [[111] axis substantially matches the normal line] as a single crystal growth substrate.
It is obtained by growing and growing a bismuth-substituted magnetic garnet single crystal film on a single crystal growth substrate by the liquid phase epitaxial (LPE) method.

The [111] axis of the (111) bismuth-substituted magnetic garnet single crystal film, in other words, the easy axis of magnetization is γ from the film normal.
For tilting, a non-magnetic substrate whose [111] axis is tilted approximately γ degrees from the normal line may be used as a single crystal growth substrate. The bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted within the range of 1 to 60 degrees with respect to the film normal is a non-magnetic garnet substrate whose [111] axis is tilted from the normal line. It is obtained by growing and growing a bismuth-substituted magnetic garnet single crystal film on a single crystal growth substrate as a substrate for liquid crystal by a liquid phase epitaxial (LPE) method. [111] of the bismuth-substituted magnetic garnet single crystal obtained here
The axis is tilted to be equal to or more than that of the single crystal growth substrate.

The non-magnetic substrate whose [111] axis is inclined by γ degrees from the normal line can be obtained by inclining the ingot by a desired inclination angle γ. The larger the tilt angle γ from the normal of the [111] axis, the smaller the number of substrates obtained from the ingot, and the more expensive the substrate. Therefore, it is preferable that the inclination angle γ from the normal line of the [111] axis is set to a value close to the minimum required value in consideration of economy from a practical viewpoint. When carrying out the present invention, the tilt angle γ of the (111) bismuth-substituted magnetic garnet single crystal film from the normal line of the [111] axis is in the range of 1 to 60 degrees, and more preferably 3 to 45 degrees. It is better to choose within the range. From a practical point of view, especially when economic is important, 3 to 20 degrees
You can choose each time. Set the tilt angle γ from the normal of the [111] axis to 1
[111] axis is tilted with respect to the membrane normal
No clear effect can be confirmed by using the (111) bismuth-substituted magnetic garnet single crystal film. That is, multiple
It is indistinguishable from the case of using a (111) bismuth-substituted magnetic garnet single crystal film in which the [111] axis substantially coincides with the film normal. On the other hand, it is economically disadvantageous if the inclination angle γ from the normal line of the [111] axis is selected to be 45 degrees or more, particularly 60 degrees or more.

In carrying out the present invention, the spatial arrangement and combination of bismuth-substituted magnetic garnet single crystal films are such that the [111] axis is tilted within the range of 1 to 60 degrees with respect to the film normal. Using a garnet single crystal film and a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis substantially coincides with the film normal, a structure according to the magnetic domain pattern and domain width of the single crystal film surface There is no particular limitation as long as Also,
In the bismuth-substituted magnetic garnet single crystal film in which the [111] axis is tilted within the range of 1 to 60 degrees with respect to the film normal, a plurality of [111] axes are 1 with respect to the film normal. Degree to 6
A stack of bismuth-substituted magnetic garnet single crystal films tilted in the range of 0 degree, or the [111] axis of a three-layer structure grown on both surfaces of a non-magnetic garnet substrate has a 1 with respect to the film normal. Bismuth-substituted magnetic garnet single crystal tilted in the range of 60 to 60 degrees, or bismuth-substituted magnetic garnet single crystal film in which the [111] axis is tilted in the range of 1 to 60 degrees with respect to the film normal. And a bismuth-substituted magnetic garnet single crystal in which the [111] axis of the three-layer structure grown on both sides of the non-magnetic garnet substrate is tilted within the range of 1 to 60 degrees with respect to the film normal. It may be

Furthermore, in the (111) bismuth-substituted magnetic garnet single crystal film in which the [111] axis is substantially coincident with the film normal, the plural [111] axes are substantially the film normal. Which are identical to each other, the (111) bismuth-substituted magnetic garnet single crystal film is laminated, or the [111] axis of the three-layer structure grown on both sides of the non-magnetic garnet substrate is substantially the same as the film normal. Bismuth-substituted magnetic garnet single crystal,
Alternatively, the [111] axis is substantially coincident with the membrane normal
The (111) bismuth-substituted magnetic garnet single crystal and the bismuth-substituted magnetic garnet single crystal in which the [111] axis of the three-layer structure grown on both sides of the non-magnetic garnet substrate substantially coincides with the film normal It may be laminated on.

That is, in the case of a bismuth-substituted magnetic garnet film whose surface has a linear magnetic domain pattern, the bismuth-substituted magnetic garnet films are closely attached so that the linear patterns intersect with each other, or they are stacked with a space (see FIG. 8). Is good. Further, bismuth-substituted magnetic garnets having different magnetic domain widths may be closely attached to each other, or a space may be provided to overlap each other. However, in the case of a bismuth-substituted magnetic garnet film in which the magnetic domain width is the same and the surface magnetic domain pattern is a maize pattern, the magnetic domains will overlap when they are brought into close contact with each other.Accordingly, depending on the characteristics of the material, an appropriate distance, More specifically, they need to be separated by about 400 μm. According to this structure, the difference ΔP in optical signal intensity required for detecting the magnetic field by the optical magnetic field sensor is at least 2 dB or more [Japanese Patent Application No. 4-90976].
Can be achieved.

In carrying out the present invention, the tilt angle of the bismuth-substituted magnetic garnet single crystal film with respect to the optical path is not particularly limited. When the influence of the surface of the bismuth-substituted magnetic garnet single crystal is large, it is preferable that the bismuth-substituted magnetic garnet single crystal is appropriately tilted so that the reflected light does not return directly to the light input / output path. . When the antireflection film is applied to the bismuth-substituted magnetic garnet single crystal and the surface reflection is sufficiently suppressed,
From the viewpoint of assembling / adjusting work, it is convenient and preferable to dispose them in a state of being almost vertical to the optical path.

In carrying out the present invention, the polarizer does not have to be a special one and may be appropriately selected and used from those generally commercially available. However, in terms of thin thickness and high extinction ratio,
In particular, a dichroic polarizer is suitable.

When carrying out the present invention, the reflective film is not particularly limited. Generally, metal thin film mirrors / mirrors that are metal-deposited on commercially available glass, bismuth-substituted magnetic garnet thin film, or gold on the surface of a non-magnetic substrate,
Alternatively, it may be appropriately selected as desired from among a metal thin film mirror in which aluminum or the like is vapor-deposited, or a dielectric multilayer film mirror formed of a multilayer film of a metal oxide such as SiO ₂ or TiO ₂ .

When the present invention is carried out, the optical input / output path does not need to be special, and is usually patterned on a commercially available optical fiber or glass or polymer film base material. It may be appropriately selected from the existing optical waveguides, air propagation paths, and the like as desired. Generally, from the viewpoint of mass productivity and downsizing, it is generally preferable to select an optical fiber.

When the optical input / output path is formed by an optical fiber,
There are no particular restrictions on the type of optical fiber used. However, the core diameter of the optical fiber used here is 50 μm.
If selected below, the effect of the magnetic domain width of the bismuth-substituted magnetic garnet may appear and the sensitivity may become unstable, or the light coupling efficiency may decrease. Therefore, generally, the purpose can be sufficiently achieved by appropriately selecting from commercially available optical fibers having a core diameter of 50 μm or more.

When the present invention is carried out, the reflection type optical magnetic field sensor head of the present invention is coupled to the light source and the photodetector by using the half mirror shown in FIG. 1 and / or FIG. The method is performed by using a signal light branching device such as an optical waveguide or an optical coupler as illustrated in FIG.
In FIG. 7, reference numeral 24 is a light source including a semiconductor laser, reference numerals 25, 28 and 29 are optical fibers, and reference numeral 26 is an optical fiber.
Reference numeral 27 denotes an optical waveguide formed on glass or a polymer, reference numeral 27 denotes an optical magnetic field sensor head including a polarizer, a plurality of bismuth-substituted magnetic garnets, and a reflective film, reference numeral 30.
Means a photodetector (power meter). In addition,
If desired, all or part of the optical fiber shown in FIG. 7 may be omitted, in other words, without using the optical fiber, for example, a reflective optical magnetic field sensor head may be directly attached to the optical waveguide. You may connect.

The wavelength of the light source of the optical magnetic field measuring device is selected in consideration of the sensitivity of the Faraday rotator, the light transmittance, the performance and cost of the light source, the sensitivity of the detector, and the like.
When the present invention is carried out, the wavelength of the light source is: -The bismuth-substituted magnetic garnet has a region called a window having a relatively small light absorption coefficient-The bismuth-substituted rare earth magnetic garnet has a large Faraday rotation coefficient-Bismuth-substituted magnetic garnet Film thickness of 30 to 100μ
It is easy to manufacture at m.-High-power short-wavelength semiconductor lasers and light-emitting diodes are available on the market at a low price.-Because of the high sensitivity of the photodetector and the availability at low cost, the wavelength range of 780 nm to 850 nm is used. It is preferable to select near infrared light. In addition, as a suboptimal measure, it is possible to select light in the wavelength bands of 1300 nm and 1550 nm, which are practically used in optical fiber communication, or in the wavelength band of 1060 nm, which can be used by YAG lasers. However, if the wavelength of the light source is
If the value deviates from the above range, there will be problems such as large optical absorption or a small Faraday rotation coefficient of the bismuth-substituted magnetic garnet, which makes it difficult to detect signal light and the film thickness of the Faraday rotator. This is not preferable because it causes various problems such as the need to increase the thickness.

Hereinafter, the present invention will be described with reference to typical examples.
The embodiments and effects thereof will be described specifically and in detail, but the following examples are for the purpose of specifically describing the embodiments and are not intended to limit the embodiments of the present invention or the scope of the invention. It has not been.

[0048]

【Example】

 Example 1 Manufactured by the Czochralski method according to a conventional method
1 inch (111) garnet single crystal [(GdCa)₃(GaMgZr)_Five
O₁₂, Ingot] [lattice constant 12.498 ± 0.002Å]
 Tilt it 5 degrees in the [112] axis and cut it so that the [111] axis is normal.
Growth of a single crystal with a thickness of 490-510 μm tilted 5 degrees
Substrate [a₁I got Similarly, the [111] axis is substantially the normal
Substrate for growing single crystal with a thickness of 480-500 μm
I got [b]. Platinum oxide [Pb
O, 4N] 843g, Bismuth oxide [Bi₂O ₃, 4N] 978g, oxidized
Ferric iron [Fe₂O₃, 4N] 128g, boron oxide [B₂O₃, 5N] 38
g, terbium oxide [Tb_FourO₇, 3N] 4.0g and oxidation
Holmium [Ho₂O₃, 3N] 9.0g was charged. Precision this
Installed in a predetermined position in a vertical tubular electric furnace and heated to 1000 ° C.
Melt, mix well, mix evenly, then melt
Bismuth-substituted magnetic garnet cooled to 768 ℃
A melt for growing a single crystal was obtained. Then, according to the usual method,
Substrate for single crystal growth [a₁],and,
Immerse the substrate [b] and keep the melt temperature at 768 ° C.
Epitaxial growth for 0.5 hours to grow a single crystal
[111] axis is tilted 5 degrees to the film normal on both sides of the substrate
Ru Ho_1.1Tb_0.6Bi_1.3Fe_FiveO₁₂Ho with single crystal film_1.1Tb
_0.6Bi_1.3Fe_FiveO ₁₂Single crystal [hereinafter, HoTbBiIG single crystal [A₁] Stands for
And the [111] axis is substantially coincident with the film normal.
Ho_1.1Tb_0.6Bi_1.3Fe_FiveO₁₂Ho with single crystal film_1.1
Tb_0.6Bi_1.3Fe_FiveO₁₂Single crystal [hereinafter, HoTbBiIG single crystal [B₁]When
Abbreviated]. HoTbBiIG single crystal obtained here
[A₁] Is 12 μm on one side and 24 μm on both sides.
Faraday rotation angle θ when saturated_FIs the wavelength 786
It was 22.2 degrees in nm and the saturation magnetic field was 1000 Oe. Well
Also, the HoTbBiIG single crystal obtained here [B₁] Is 13μ on one side
m, the thickness of both sides is 26 μm, and the magnetization is saturated.
Faraday rotation angle θ_FIs 23.1 degrees at a wavelength of 786 nm.
The saturation magnetic field was 1000 Oe.

On one HoTbBiIG single crystal surface of the HoTbBiIG single crystal [A ₁ ] obtained here, aluminum was vapor-deposited by a vapor deposition method to form a reflection film, that is, a mirror, and then the other HoTbBiIG single crystal surface. Then, after applying an anti-reflection film by the usual method, the specified size [2.5 mm × 2.5 mm]
It was cut into pieces to obtain a HoTbBiIG single crystal [A ₁ ] -reflection film block. Then, on both sides of the HoTbBiIG single crystal film of HoTbBiIG single crystal [B ₁ ], by an ordinary method, after applying an antireflection film, it is cut into a predetermined size [2.5 mm × 2.5 mm] HoTbBiIG single crystal [B 1 ₁ ] I got a piece.

Subsequently, the obtained HoTbBiIG single crystal [B ₁ ] piece was converted into a HoTbBiIG single crystal [A ₁ ] -reflection film block.
The Faraday rotator-reflection film block was obtained by closely contacting with the HoTbBiIG single crystal film surface and fixing and bonding with a commercially available optical adhesive.

From the Faraday rotator-reflecting film block obtained here, five were randomly selected and the H
oTbBiIG single crystal [B ₁ ] film surface is attached with an antireflection film polarizer [Corning Co., trade name POLACORE], fixed with an epoxy-based adhesive to bond, polarizer-
A Faraday rotator [A ₁ -B ₁ ] -reflection film block was obtained. An optical magnetic field sensor head was obtained by attaching a polymer clad optical fiber having a core diameter of 400 μm as an optical input / output path to the obtained polarizer / Faraday rotator / reflection film block.

The optical magnetic field sensor head obtained here was attached to the optical magnetic field sensor head terminal of the reflection type optical magnetic field sensor [see FIG. 1]. The tip of the optical magnetic field sensor head was set at a predetermined position of a magnetic field applying device [MAGNET, manufactured by Magnetic Co., Ltd.]. The light source [semiconductor laser, manufactured by Sharp,
Product name Laser diode, LT024MD / PD type] wavelength 0.786μ
The signal light of m 2 was emitted, and the signal light was made incident on the above-mentioned optical magnetic field sensor head through a lens, a half mirror, and an optical input / output path [optical fiber having a core diameter of 400 μm]. Then, it is reflected by the optical magnetic field sensor head, and again, a part of the optical signal emitted from the optical fiber is reflected by a half mirror to detect a photodetector (manufactured by Ando Electric Co., Ltd., power meter, AQ-1111).
Mold], and the light intensity of the signal light that reached here was measured. As a result, the Faraday rotator has a magnetic field strength of 1000 Oe.
The Faraday rotator was magnetically saturated when a magnetic field of 1 was applied. The difference in light intensity between the state in which no magnetic field was applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator was 2.5 dB to 2.6 dB (average value 2.5 dB).

Example 2 Example 1 was the same as Example 1 except that one side of the single crystal growth substrate [a ₁ ] was brought into contact with the surface of the single crystal growth melt to carry out epitaxial growth for 1.0 hour. By the same treatment, Ho _1.1 Tb _0.6 Bi _1.3 Fe is formed on one surface of the single crystal growth substrate [a ₁ ].
A Ho _1.1 Tb _0.6 Bi _1.3 Fe ₅ O ₁₂ single crystal [hereinafter abbreviated as HoTbBiIG single crystal [A ₂ ]] having a ₅ O ₁₂ single crystal film was obtained. The film thickness of the HoTbBiIG single crystal [A ₂ ] obtained here was 23 μm. The Faraday rotation angle θ _{F in} the state where the magnetization was saturated was 21.7 degrees at the wavelength of 786 nm. On the surface of the substrate [a ₁ ] of the HoTbBiIG single crystal [A ₂ ] obtained here, aluminum was vapor-deposited by a vapor deposition method to form a reflection film, that is, a mirror, and then the HoTbBiIG single crystal was formed by a conventional method.
After applying an antireflection film on the surface of [A ₂ ], it is cut into a predetermined size [2.5 mm × 2.5 mm] and HoTbBiIG single crystal [A ₂ ]-
A reflective film block was obtained.

HoTbBiIG single crystal obtained here [A₂] -Anti
From the film block, randomly select 5 blocks and
HoTbBiIG single crystal obtained in Example 1 [B₁] Piece is HoTbBiIG single bond
Crystal [A ₂] -Reflective film block HoTbBiIG single crystal [A₂] On the membrane surface
Adhere closely and fix with a commercially available optical adhesive to join
Let Next, HoTbBiIG single crystal [B₁] Reflection on the surface of the film
Polarizer coated with an anti-reflection film
Core] and attach and fix with epoxy adhesive
Let the Polarizer-Faraday rotator [A₂-B₁] -Reflective film block
I got a hook. Polarizer obtained here-Faraday rotator
− A core diameter of 400 μm as an optical input / output path in the reflective film block
Optical field sensor with attached polymer clad optical fiber
Got the head.

The optical magnetic field sensor head obtained here was attached to the optical magnetic field sensor head terminal of the test apparatus used in Example 1, and an evaluation test was conducted in the same manner as in Example 1. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator, the Faraday rotator was magnetically saturated. Also, the light intensity difference between the state in which no magnetic field is applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe is applied to the Faraday rotator is 2.8 dB to 3.0 dB (average value).
It was 2.9 dB).

Example 3 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it 3 degrees in the [112] axis direction
Substrate for growing single crystal in which the [111] axis is tilted 3 degrees with respect to the normal line
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that [a ₃ ] was used, and an evaluation test was performed in the same manner as in Example 1. As a result, the Faraday rotator was magnetically saturated when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₃ -B ₁ ]. In addition, when the magnetic field is not applied to the Faraday rotator, the magnetic field strength 1
The difference in light intensity from the state in which a magnetic field of 000 Oe was applied was 2.2 dB to 2.5 dB (average value 2.3 dB).

Example 4 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it by 10 degrees in the [112] axis direction
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that the single crystal growth substrate [a ₄ ] whose [111] axis was tilted by 10 degrees with respect to the normal was used. An evaluation test was conducted in the same manner. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₄ -B ₁ ], the Faraday rotator was magnetically saturated. In addition, when the magnetic field is not applied to the Faraday rotator,
2.8 dB difference in light intensity when a magnetic field of 1000 Oe is applied
It was 3.3 dB (average value 3.0 dB).

Example 5 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it by 20 degrees in the [112] axis direction
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that the single crystal growth substrate [a ₅ ] whose [111] axis was tilted at 20 degrees with respect to the normal was used. An evaluation test was conducted in the same manner. As a result, the Faraday rotator was magnetically saturated when a magnetic field of 1000 Oe was applied to the Faraday rotator [A ₅ -B ₁ ]. In addition, when the magnetic field is not applied to the Faraday rotator,
The light intensity difference from the state where a magnetic field of 1000 Oe is applied is 3.0 dB.
To 3.4 dB (average value 3.2 dB).

Example 6 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it by 40 degrees in the [112] axis direction
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that the single crystal growth substrate [a ₆ ] in which the [111] axis was tilted 40 degrees with respect to the normal was used. An evaluation test was conducted in the same manner. As a result, the Faraday rotator was magnetically saturated when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₆ -B ₁ ]. In addition, when the magnetic field is not applied to the Faraday rotator,
The difference in light intensity from the state where a magnetic field of 1000 Oe is applied is 3.6 dB.
To 4.1 dB (average value 3.8 dB).

Example 7 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it by 60 degrees in the [112] axis direction
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that the single crystal growth substrate [a ₇ ] whose [111] axis was tilted at 60 degrees with respect to the normal was used. An evaluation test was conducted in the same manner. As a result, the Faraday rotator was magnetically saturated when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₇ -B ₁ ]. In addition, when the magnetic field is not applied to the Faraday rotator,
3.3 dB difference in light intensity from the state where a magnetic field of 1000 Oe was applied
To 3.5 dB (average value 3.4 dB).

Example 8 Platinum oxide [PbO 4N] 843 was placed in a platinum crucible having a capacity of 500 ml.
g, bismuth oxide [Bi₂O₃, 4N] 978g, ferric oxide [Fe₂O
₃ , 4N] 120 g, gallium oxide [Ga₂O₃ , 4N] 4.5 g, oxidized
Boron [B₂O₃, 5N] 38g, Gadolinium oxide [Gd₂O₃ ,
3N] 6.5 g and yttrium oxide [Y₂O₃, 3N] 4.0g
Was charged. Place this in place on the precision vertical tubular electric furnace.
Install, heat to 1000 ℃ to melt, stir well and homogenize
And melt to a melt temperature of 773 ° C.
It was used as a melt for growing a mass-substituted magnetic garnet single crystal. Next
Then, according to a conventional method, the melt obtained in
The obtained single crystal growth substrate [b] is immersed and the melt temperature is 773 ° C.
Epitaxial growth for 0.7 hours while maintaining
Y on both sides of the single crystal growth substrate [b]_0.9Gd_0.9Bi_1.2Fe_Four
.8Ga_0.2O₁₂Y with single crystal [YGdBiGaIG single crystal] film
_0.9Gd_0.9Bi_1.2Fe_4.8Ga_0.2O ₁₂Single crystal (hereinafter, YGdBiGaIG
Single crystal [B₂]]] A film was obtained. YGd obtained here
BiGaIG single crystal [B₂] Is 16 μm on one side and 32 μ on both sides
Faraday rotation angle θ when the magnetization is saturated at m_F
Was 24.4 degrees at a wavelength of 786 nm. Also, the saturation magnetic field is
 It was 600 Oe. Then, according to the conventional method, YGdBiGaIG
Single crystal [B₂] After applying anti-reflection film on both sides,
YGdBiGaIG single crystal [B
₂I got a piece

From the YGdBiGaIG single crystal [B ₂ ] pieces obtained here, five pieces were randomly selected, and H obtained in Example 1 was selected.
The oTbBiIG single crystal [A ₁ ] -reflection film block was closely adhered to the HoTbBiIG single crystal film surface, and fixed and bonded using a commercially available optical adhesive. Then, on the surface of the YGdBiGaIG single crystal [B ₂ ] film, an antireflection film-provided polarizer [Corning Co., Ltd., trade name POLACORE] was attached, and fixed and bonded with an epoxy adhesive to form a polarizer- Faraday rotator [A ₁ -B ₂ ]
-A reflective film block is obtained. An optical magnetic field sensor head was obtained by attaching a polymer clad optical fiber having a core diameter of 400 μm as an optical input / output path to the obtained polarizer / Faraday rotator / reflection film block.

The optical magnetic field sensor head obtained here is a reflection type optical magnetic field sensor constituted by an optical branching device [200S-D2 type manufactured by Mitsubishi Gas Chemical Co., Ltd.] made of a polymer optical waveguide [see FIG. 7]. ] Optical input / output path [optical fiber with a core diameter of 200 μm]
Attached to. The tip of the optical magnetic field sensor head was set at a predetermined position of a magnetic field applying device [MAGNET, manufactured by Magnetic Co., Ltd.]. While varying the magnetic field application state of the optical magnetic field sensor head, a laser beam with a wavelength of 0.786 μm was made incident from the light source to reach the photodetector (manufactured by Ando Electric Co., Ltd., product name Power Meter, AQ-1111 type). The light intensity of the signal light was measured. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator, the Faraday rotator was magnetically saturated. The difference in light intensity between the state in which no magnetic field is applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe is applied to the Faraday rotator is 3.5 dB to 3.8 dB (average value).
It was 3.7 dB).

Example 9 In Example 8, the HoTbBiIG) single crystal obtained in Example 1 [A
₁ ] -HoTbBiI obtained in Example 3 instead of the reflective film block
G) single crystal [A _3] - except that a reflective film block, an evaluation test was conducted in the same manner as in Example 8. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₃ -B ₂ ], the Faraday rotator was magnetically saturated. The difference in light intensity between the state in which no magnetic field was applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator was 3.0 dB to 3.5 dB (average value 3.3 dB).

Example 10 In Example 8, the HoTbBiIG single crystal obtained in Example 1 [A
₁ ] -HoTbBiI obtained in Example 7 instead of the reflective film block
An evaluation test was conducted in the same manner as in Example 8 except that the G single crystal [A ₇ ] -reflection film block was used. As a result, the Faraday rotator was magnetically saturated when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₇ -B ₂ ]. The light intensity difference between the state where no magnetic field was applied to the Faraday rotator and the state where a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator was 2.7 dB to 3.1 dB (average value 2.8 dB).

Example 11 First, a platinum crucible having a capacity of 500 ml was placed in a lead oxide [PbO 4,
N] 843 g, bismuth oxide [Bi ₂ O ₃ , 4N] 978 g, second oxide
Iron [Fe ₂ O ₃ , 4N] 120 g, gallium oxide [Ga ₂ O ₃ , 4N] 4.
5g, boron oxide [B ₂ O ₃ , 5N] 38g, gadolinium oxide [Gd ₂ O ₃ , 3N] 6.5g, and yttrium oxide [Y
₂ O ₃ , 3N] 4.0 g was charged. This was placed in a predetermined position in a precision vertical tubular electric furnace, heated to 1000 ° C to melt it, stirred well and mixed uniformly, then cooled to a melt temperature of 773 ° C and bismuth-substituted magnetic. The melt was used for growing a garnet single crystal. Then, according to a conventional method, the single crystal growth substrate [a ₁ ] obtained in Example 1 was immersed in the melt obtained here, and the epitaxial growth was performed for 0.7 hours while maintaining the melt temperature at 773 ° C. On both sides of the single crystal growth substrate.
1] axis is tilted 5 degrees to the membrane normal Y _0.9 Gd _0.9 Bi _1.2 F
e _4.8 Ga _0.2 O ₁₂ Y has a single-crystal film _{0.9 Gd 0.9 Bi 1.2 Fe 4 .8} Ga
_{A 0.2} O ₁₂ single crystal [hereinafter, abbreviated as YGdBiGaIG single crystal [A ₈ ]] was obtained. The YGdBiGaIG single crystal [A ₈ ] obtained here is
The Faraday rotation angle θ _F when the magnetization is saturated is 15 μm on one side and 30 μm on both sides.
It was 7 degrees and the saturation magnetic field was 600 Oe.

On one YGdBiGaIG single crystal surface of the YGdBiGaIG single crystal [A ₈ ] obtained here, aluminum was vapor-deposited by a vapor deposition method to form a reflection film, that is, a mirror, and then the other YGdBiGaIG single crystal surface. Then, after applying an anti-reflection film by the usual method, the specified size [2.5 mm × 2.5 mm]
It was cut into YGdBiGaIG single crystal [A ₈ ] -reflection film block. From the YGdBiGaIG single crystal [A ₈ ] -reflecting film blocks obtained here, five were randomly selected and the YGdBiGaIG single crystal [B ₂ ] piece obtained in Example 8 was used as the YGdBiGaIG single crystal film surface. They were brought into close contact with each other and fixed and joined using a commercially available optical adhesive. Then, on the surface of the YGdBiGaIG single crystal [B ₂ ] film, an antireflection film-provided polarizer [Corning Co., Ltd., trade name POLACORE] was attached, and fixed and bonded with an epoxy adhesive to form a polarizer- Faraday rotator [a ₈ -B _2] - was obtained reflective film blocks. Hereinafter, an optical magnetic field sensor head was manufactured in the same manner as in Example 8 and an evaluation test was performed in the same manner as in Example 8. As a result, when a magnetic field with a magnetic field strength of 600 Oe was applied to the Faraday rotator [A ₈ -B ₈ ], the Faraday rotator was magnetically saturated. In addition, when the magnetic field is not applied to the Faraday rotator, the magnetic field strength 6
The difference in light intensity from the state in which a magnetic field of 00 Oe is applied is 4.5 dB or more.
It was 4.6 dB (average value 4.6 dB).

Comparative Example 1 HoTbBiIG single crystal obtained in Example 1 [B₁] One HoT
Aluminum is vapor-deposited on the surface of bBiIG single crystal.
After forming a reflection film, that is, a mirror, the other
 An anti-reflection film was formed on the HoTbBiIG single crystal surface by a conventional method.
Then, cut it to a specified size [2.5 mm × 2.5 mm] and HoT
bBiIG single crystal [A₉] -A reflective film block was obtained. Got here
HoTbBiIG single crystal [A₉] -From the reflective film block,
HoTbBiIG obtained in Example 1 by randomly selecting 5 pieces
Single crystal [B₁] Pieces of HoTbBiIG single crystal [A ₉] Adhere to the film surface
Then, they were fixed and joined using a commercially available optical adhesive.
Next, HoTbBiIG single crystal [B₁] An antireflection film on the surface of the film
The applied polarizer (made by Corning, trade name Polar Core)
Attach, fix with epoxy adhesive and join,
Polarizer-Faraday rotator [A₉-B₁] -Reflective film block
Obtained. Polarizer obtained here-Faraday rotator-reflection
The membrane block has a core with a core diameter of 400 μm
Optical field sensor head with attached maclad optical fiber
Got Then, an evaluation test is conducted in the same manner as in Example 1.
It was As a result, the Faraday rotator [A₉-B₁] To magnetic field strength 1
When a magnetic field of 000 Oe is applied, the Faraday rotator
It was saturated. Also, apply a magnetic field to the Faraday rotator.
The magnetic field strength of 1000 Oe to the Faraday rotator.
Light intensity difference from the state where a magnetic field is applied is 1.7 dB to 2.1 dB
(Average value 1.8 dB).

Comparative Example 2 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it once in the [112] axis direction
Substrate for growing single crystal in which the [111] axis is inclined by 1 degree with respect to the normal line
An optical magnetic field sensor head was produced in the same manner as in Example 1 except that [a ₁₀ ] was used, and an evaluation test was performed in the same manner as in Example 1. As a result, the Faraday rotator was magnetically saturated when a magnetic field having a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₁₀ -B ₁ ]. In addition, when the magnetic field is not applied to the Faraday rotator,
1.8 dB difference in light intensity when a magnetic field of 1000 Oe is applied
It was 2.1 dB (average value 2.0 dB).

Comparative Example 3 In Example 1, in cutting the single crystal growth substrate,
Obtained by cutting the ingot by tilting it 65 degrees to the [112] axis
An optical magnetic field sensor head was manufactured in the same manner as in Example 1 except that the single crystal growth substrate [a ₁₁ ] whose [111] axis was inclined by 65 degrees with respect to the normal was used. An evaluation test was conducted in the same manner. As a result, the Faraday rotator was magnetically saturated when a magnetic field having a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₁₁ -B ₁ ]. The difference in light intensity between the state in which no magnetic field is applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe is applied to the Faraday rotator is 3.2.
dB to 3.5 dB (average value 3.3 dB).

Comparative Example 4 The HoTbBiIG single crystal [A ₁ ] in Example 8 was replaced with the HoTbBiIG single crystal [A ₁₀ ] obtained in Comparative Example 2 instead of the reflective film block.
An optical magnetic field sensor head was manufactured in the same manner as in Example 8 except that the reflective film block was used, and an evaluation test was performed in the same manner as in Example 1. As a result, the Faraday rotator [A
_When a magnetic field with a magnetic field strength of 1000 Oe is applied to [ ₁₀ -B ₂ ],
The Faraday rotator was magnetically saturated. The difference in light intensity between the state in which no magnetic field was applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator was 1.8 dB to 2.1 dB (average value 2.0 dB).

[0072]

According to the present invention, a small and lightweight reflective magneto-optical sensor head can be industrially and extremely easily manufactured and provided using a magneto-optical material having a multi-domain structure.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a reflective optical magnetic field sensor disclosed in Japanese Patent Publication No. 3-22595.

FIG. 2 is a schematic diagram showing a configuration of a reflective optical magnetic field sensor disclosed in Japanese Patent Application No. 4-90976.

FIG. 3 is a schematic diagram for specifically explaining the basic configuration of the reflective optical magnetic field sensor head of the present invention.

FIG. 4 The [111] axis of the present invention is tilted with respect to the film normal.
A Faraday rotator composed of a (111) bismuth-substituted magnetic garnet single crystal film and a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis substantially coincides with the film normal is
It is a schematic diagram which shows the relationship between the position of an optical path and a magnetic domain, and a magnetization direction when arrange | positioning perpendicularly with respect to an optical input / output path [optical path].

FIG. 5: The [111] axis substantially coincides with the membrane normal (11
1) When the Faraday rotator composed of a bismuth-substituted magnetic garnet film is arranged to be inclined with respect to the optical input / output path (optical path, optical axis), the optical path [optical axis], the normal line, the position of the magnetic domain, and the magnetization direction It is a schematic diagram which shows the relationship of.

[FIG. 6] A Faraday rotator composed of a (111) bismuth-substituted magnetic garnet film in which the [111] axis is inclined with respect to the film normal is arranged perpendicular to the optical input / output path [optical path, optical axis]. FIG. 6 is a schematic diagram showing the relationship among the optical path [optical axis], the normal line, the position of the magnetic domain, and the magnetization direction at that time.

FIG. 7 shows a Faraday rotator composed of a (111) bismuth-substituted magnetic garnet single crystal film whose two [111] axes substantially coincide with the film normal to an optical input / output path [optical path]. It is a schematic diagram which shows the relationship between the optical path and the position of a magnetic domain, and a magnetization direction when arrange | positioning perpendicularly.

FIG. 8 is a schematic diagram showing an example of a Faraday rotator on which a bismuth-substituted magnetic garnet film having a linear magnetic domain pattern is superposed.

FIG. 9 is a schematic diagram showing an example of the overall configuration of an optical magnetic field sensor using the reflective optical magnetic field sensor head of the present invention.

[Explanation of symbols]

 1 ・ ・ ・ Light source 2 ・ ・ ・ Lens 3 ・ ・ ・ Half mirror 4 ・ ・ ・ Optical fiber 5 ・ ・ ・ Lens 6 ・ ・ ・ Polarizer 7 ・ ・ ・ Faraday rotator 8 ・ ・ ・ Reflective film 9 ・ ・ ・Photodetector 10 ・ ・ ・ Polarizer 11 ・ ・ ・ Faraday rotator 12 ・ ・ ・ Reflective film 13 ・ ・ ・ Optical input path 14 ・ ・ ・ Optical output path 15 ・ ・ ・ Lens 16 ・ ・ ・ Light source 17 ・ ・ ・Photodetector 18 ・ ・ ・ Polarizer 19 ・ ・ ・ Faraday rotator 20 ・ ・ ・ Reflective film 21 ・ ・ ・ Optical input / output path 22 ・ ・ ・ Bismuth-substituted magnetic garnet 23 ・ ・ ・ Bismuth-substituted magnetic garnet 24 ・ ・ ・Bismuth-substituted magnetic garnet 25 ・ ・ ・ Bismuth-substituted magnetic garnet 26 ・ ・ ・ Light source 27 ・ ・ ・ Optical fiber 28 ・ ・ ・ Optical waveguide 29 ・ ・ ・ Optical magnetic field sensor head 30 ・ ・ ・ Optical input / output path 31 ・ ・ ・ Optical Fa IVA 32 ・ ・ ・ Photodetector

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

In practicing the present invention, a Faraday rotator is a bismuth-substituted magnetic material in which the [111] axes of the same or different types are tilted within a range of 1 to 60 degrees with respect to the film normal. It must consist of a garnet single crystal film and a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis is substantially aligned with the film normal. However, the [111] axis is substantially coincident with the film normal with the bismuth-substituted magnetic garnet single crystal film in which the [111] axis is inclined within the range of 1 to 60 degrees with respect to the film normal ( 111) Bismuth-substituted magnetic garnet single-crystal film, other configurations, for example, which is to be arranged on the light source side and combinations, and (111) Bismuth-substituted magnetic garnet single-crystal film configuration The number of sheets is not particularly limited. Therefore, when carrying out the present invention, the type and configuration of the bismuth-substituted magnetic garnet single crystal film constituting the Faraday rotator and the number of constituents may be appropriately selected in consideration of the performance and characteristics required for the Faraday rotator. .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

The (111) bismuth-substituted magnetic garnet single crystal film used in the present invention can be manufactured by a known method. Liquid phase epitaxial (LPE) method [Sin Solid]
Films (Thin Solid Films), Vol.114, p33 (1984)
] Is preferred. When carrying out the liquid phase epitaxial method, any known substrate can be used as the single crystal growth substrate, but generally, the lattice constant which is already commercially available as SGGG substrate is 12.490 Å. , Or 1
2.515 Å non-magnetic garnet [(GdCa) ₃ (GaMgZr) ₅ O ₁₂ ]
It is preferable to appropriately select from among these.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

In carrying out the present invention, the reflection type of the present invention
Coupling of optical magnetic field sensor head with light source and photodetector
Is a method using the half mirror shown in FIG.
Or9Optical waveguides and optical couplers
Etc. by using a signal light branching device.
Figure9Where the sign26Is a light source consisting of a semiconductor laser, etc.
The sign27And sign30And sign31Code optical fiber28
Is an optical waveguide formed on glass or polymer
The sign29Is a polarizer and multiple bismuth-substituted magnetic gauze
Optical magnetic field sensor head consisting of32
Means a photodetector (power meter). In addition,
Figure, if desired9All of the optical fibers shown in
Or, omit a part of it, in other words, use an optical fiber
Without using, for example, a reflective magneto-optical field
The sensor head may be directly connected.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0063

[Correction method] Change

[Correction content]

The optical magnetic field sensor head obtained here is constituted by an optical branching device (200S-D2 type manufactured by Mitsubishi Gas Chemical Co., Inc.) made of a polymer optical waveguide, and a reflection type optical magnetic field sensor [Fig.
9 )] Optical input / output path [optical fiber with a core diameter of 200 μm]
Attached to. The tip of the optical magnetic field sensor head was set at a predetermined position of a magnetic field applying device [MAGNET, manufactured by Magnetic Co., Ltd.]. While varying the magnetic field application state of the optical magnetic field sensor head, a laser beam with a wavelength of 0.786 μm was made incident from the light source to reach the photodetector (manufactured by Ando Electric Co., Ltd., product name Power Meter, AQ-1111 type). The light intensity of the signal light was measured. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator, the Faraday rotator was magnetically saturated. The difference in light intensity between the state in which no magnetic field is applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe is applied to the Faraday rotator is 3.5 dB to 3.8 dB (average value).
It was 3.7 dB).

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0064

[Correction method] Change

[Correction content]

Example 9 In Example 8, the HoTbBiIG single crystal obtained in Example 1 [A
₁ ] -HoTbBiI obtained in Example 3 instead of the reflective film block
An evaluation test was conducted in the same manner as in Example 8 except that the G single crystal [A ₃ ] -reflection film block was used. As a result, when a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator [A ₃ -B ₂ ], the Faraday rotator was magnetically saturated. The difference in light intensity between the state in which no magnetic field was applied to the Faraday rotator and the state in which a magnetic field with a magnetic field strength of 1000 Oe was applied to the Faraday rotator was 3.0 dB to 3.5 dB (average value 3.3 dB). ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

Means for Solving the Problems The inventors of the present application improved technical defects and defects left in the reflection type optical magnetic field sensor proposed by the inventors of the present application, and immediately measured an accurate rotation speed. It is highly reliable, and more specifically, it is small and lightweight, highly accurate, easy to handle, and can withstand long-term continuous use in harsh environments such as high temperature and vibration. Moreover, by providing an inexpensive tachometer / measuring device, we have earnestly studied and conducted experiments to contribute to the international social demand for global environment protection and energy saving. As a result, first of all, the reason why the previously proposed reflective optical magnetic field sensor [Japanese Patent Application No. 4-174357] is mixed with a product that does not function sufficiently as a reflective optical magnetic field sensor,
We have found that there is a relative optical positional relationship between the optical path and the bismuth-substituted magnetic garnet single crystal film that constitutes the Faraday rotator, that is, it is caused by omitting the optical fine adjustment and alignment operations.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

As a practical matter, it is not easy to carry out the optical fine adjustment / alignment operation in the industrial manufacture of the reflection type optical magnetic field sensor. Therefore, the inventors of the present application have conducted earnest study experiments in order to develop a technique that replaces the optical adjustment / alignment operation. As a result, as the Faraday rotator, the bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted within the range of 1 to 60 degrees with respect to the film normal and the [111] axis is substantially the film normal. By using a Faraday rotator composed of multiple (111) bismuth-substituted magnetic garnet single crystal films and (111) bismuth-substituted magnetic garnet single crystal films that match each other. Based on the finding that the above can be substantially avoided, the inventors of the present invention have completed the present invention by conducting further diligent improvement research, reliability confirmation experiments, and trial production. That is, in the present invention, in the optical magnetic field measurement device in which the optical input / output path, the polarizer, the Faraday rotator, and the reflective film are arranged in this order, the reflective film is
The Faraday rotator is arranged almost perpendicular to the optical path center of the optical input / output path, and the Faraday rotator has a [111] axis tilted within the range of 1 to 60 degrees with respect to the film normal. It is composed of a plurality of (111) bismuth-substituted magnetic garnet single crystal films with a substituted magnetic garnet single-crystal film and a (111) bismuth-substituted magnetic garnet single-crystal film whose [111] axis substantially coincides with the film normal. Reflective optical magnetic field sensor head.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction content]

On one YGdBiGaIG single crystal surface of the YGdBiGaIG single crystal [A ₈ ] obtained here, aluminum was vapor-deposited by a vapor deposition method to form a reflection film, that is, a mirror, and then the other YGdBiGaIG single crystal surface. Then, after applying an anti-reflection film by the usual method, the specified size [2.5 mm × 2.5 mm]
It was cut into YGdBiGaIG single crystal [A ₈ ] -reflection film block. From the YGdBiGaIG single crystal [A ₈ ] -reflecting film blocks obtained here, five were randomly selected and the YGdBiGaIG single crystal [B ₂ ] piece obtained in Example 8 was used as the YGdBiGaIG single crystal film surface. They were brought into close contact with each other and fixed and joined using a commercially available optical adhesive. Then, on the surface of the YGdBiGaIG single crystal [B ₂ ] film, an antireflection film-provided polarizer [Corning Co., Ltd., trade name POLACORE] was attached, and fixed and bonded with an epoxy adhesive to bond the polarizer- Faraday rotator [a ₈ -B _2] - was obtained reflective film blocks. Hereinafter, an optical magnetic field sensor head was manufactured in the same manner as in Example 8 and an evaluation test was performed in the same manner as in Example 8. As a result, when a magnetic field with a magnetic field strength of 600 Oe was applied to the Faraday rotator [A ₈ -B ₂ ] , the Faraday rotator was magnetically saturated. In addition, when the magnetic field is not applied to the Faraday rotator, the magnetic field strength 6
The difference in light intensity from the state in which a magnetic field of 00 Oe is applied is 4.5 dB or more.
It was 4.6 dB (average value 4.6 dB).

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

Comparative Example 1 HoTbBiIG single crystal obtained in Example 1 [B₁] One HoT
Aluminum is vapor-deposited on the surface of bBiIG single crystal.
After forming a reflection film, that is, a mirror, the other
 An anti-reflection film was formed on the HoTbBiIG single crystal surface by a conventional method.
Then, cut it to a specified size [2.5 mm × 2.5 mm] and HoT
bBiIG single crystal[B ₁ ]-A reflective film block is obtained. Got here
HoTbBiIG single crystal[B ₁ ]-From the reflective film block,
HoTbBiIG obtained in Example 1 by randomly selecting 5 pieces
Single crystal [B₁] Pieces of HoTbBiIG single crystal[B ₁]Close contact with the film surface
Then, they were fixed and joined using a commercially available optical adhesive.
Next, HoTbBiIG single crystal [B₁] An antireflection film on the surface of the film
The applied polarizer (made by Corning, trade name Polar Core)
Attach, fix with epoxy adhesive and join,
Polarizer-Faraday rotator[B _1- B₁] -Reflective film block
Obtained. Polarizer obtained here-Faraday rotator-reflection
The membrane block has a core with a core diameter of 400 μm
Optical field sensor head with attached maclad optical fiber
Got Then, an evaluation test is conducted in the same manner as in Example 1.
It was As a result, the Faraday rotator[B _1- B₁] To magnetic field strength 1
When a magnetic field of 000 Oe is applied, the Faraday rotator
It was saturated. Also, apply a magnetic field to the Faraday rotator.
The magnetic field strength of 1000 Oe to the Faraday rotator.
Light intensity difference from the state where a magnetic field is applied is 1.7 dB to 2.1 dB
(Average value 1.8 dB).

[Procedure amendment]

[Submission date] August 5, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a reflective optical magnetic field sensor disclosed in Japanese Patent Publication No. 3-22595.

FIG. 2 is a schematic diagram showing a configuration of a reflective optical magnetic field sensor disclosed in Japanese Patent Application No. 4-90976.

FIG. 3 is a schematic diagram for specifically explaining the basic configuration of the reflective optical magnetic field sensor head of the present invention.

FIG. 4 The [111] axis of the present invention is tilted with respect to the film normal.
A Faraday rotator composed of a (111) bismuth-substituted magnetic garnet single crystal film and a (111) bismuth-substituted magnetic garnet single crystal film whose [111] axis substantially coincides with the film normal is
It is a schematic diagram which shows the relationship between the position of an optical path and a magnetic domain, and a magnetization direction when arrange | positioning perpendicularly with respect to an optical input / output path [optical path].

FIG. 5: The [111] axis substantially coincides with the membrane normal (11
1) When the Faraday rotator composed of a bismuth-substituted magnetic garnet film is arranged to be inclined with respect to the optical input / output path (optical path, optical axis), the optical path [optical axis], the normal line, the position of the magnetic domain, and the magnetization direction It is a schematic diagram which shows the relationship of.

[FIG. 6] A Faraday rotator composed of a (111) bismuth-substituted magnetic garnet film in which the [111] axis is inclined with respect to the film normal is arranged perpendicular to the optical input / output path [optical path, optical axis]. FIG. 6 is a schematic diagram showing the relationship among the optical path [optical axis], the normal line, the position of the magnetic domain, and the magnetization direction at that time.

FIG. 7 shows a Faraday rotator composed of a (111) bismuth-substituted magnetic garnet single crystal film whose two [111] axes substantially coincide with the film normal to an optical input / output path [optical path]. It is a schematic diagram which shows the relationship between the optical path and the position of a magnetic domain, and a magnetization direction when arrange | positioning perpendicularly.

FIG. 8 is a schematic diagram showing an example of a Faraday rotator on which a bismuth-substituted magnetic garnet film having a linear magnetic domain pattern is superposed.

FIG. 9 is a schematic diagram showing an example of the overall configuration of an optical magnetic field sensor using the reflective optical magnetic field sensor head of the present invention.

[Explanation of Codes] 1 ... Light source 2 ... Lens 3 ... Half mirror 4 ... Optical fiber 5 ... Lens 6 ... Polarizer 7 ... Faraday rotator 8 ... Reflection Film 9 ... Photodetector 10 ... Polarizer 11 ... Faraday rotator 12 ... Reflective film 13 ... Optical input path 14 ... Optical output path 15 ... Lens 16 ... Light source 17 ・ ・ ・ Photodetector 18 ・ ・ ・ Polarizer 19 ・ ・ ・ Faraday rotator 20 ・ ・ ・ Reflective film 21 ・ ・ ・ Optical input / output path 22 ・ ・ ・ Bismuth substitution magnetic garnet 23 ・ ・ ・ Bismuth substitution magnetism Garnet 24 ・ ・ ・ Bismuth-substituted magnetic garnet 25 ・ ・ ・ Bismuth-substituted magnetic garnet 26 ・ ・ ・ Light source 27 ・ ・ ・ Optical fiber 28 ・ ・ ・ Optical waveguide 29 ・ ・ ・ Optical magnetic field sensor head 30 ・ ・ ・ Optical input / output path Three 1 ... Optical fiber 32 ... Photodetector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Shimono Sanyo Gas Chemical Co., Ltd. 2-5-2 Marunouchi, Chiyoda-ku, Tokyo

Claims (6)

[Claims] 1. An optical input / output path, a polarizer, a Faraday rotator,
In the optical magnetic field measurement device arranged in the order of the reflection film, the reflection mirror is arranged almost perpendicular to the optical path center of the optical input / output path, and the Faraday rotator
A bismuth-substituted magnetic garnet single crystal film in which the [1] axis is inclined within a range of 1 to 60 degrees with respect to the film normal, and the [111] axis is substantially aligned with the film normal (111) bismuth A reflection type optical magnetic field sensor head, which is composed of a plurality of (111) bismuth substituted magnetic garnet single crystal films with a substituted magnetic garnet single crystal film. 2. A polarizer, a Faraday rotator, and a reflective film with a (111) garnet single crystal substrate interposed, or
2. The reflection type optical magnetic field sensor head according to claim 1, wherein the reflection type optical magnetic field sensor head is integrally formed so as to be in close contact without being interposed. 3. A Faraday rotator comprising a bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted within a range of 1 ° to 60 ° with respect to the film normal and a [111] axis being the film normal. 2. A (111) bismuth-substituted magnetic garnet single-crystal film that is substantially identical to the (111) bismuth-substituted magnetic garnet single-crystal film.
And the reflection type optical magnetic field sensor head according to claim 2. 4. A Faraday rotator having a bismuth-substituted magnetic garnet single crystal film whose [111] axis is tilted within a range of 3 to 45 degrees with respect to a film normal and a [111] axis being a film normal. 4. The reflection type optical magnetic field sensor head according to claim 1, wherein the reflection type optical magnetic field sensor head is composed of a (111) bismuth-substituted magnetic garnet single crystal film that substantially corresponds to . 5. The [111] axis has a degree of 1 to 6 with respect to the film normal.
The (111) bismuth-substituted magnetic garnet single crystal film which is tilted within the range of 0 degree or whose [111] axis substantially coincides with the film normal is a (111) garnet single crystal substrate. The reflection type optical magnetic field sensor head according to any one of claims 1, 2 and 3, which is a (111) bismuth-substituted magnetic garnet single crystal having a three-layer structure grown and formed on both surfaces. 6. A Faraday rotator having two different chemical compositions.
6. The reflection type optical magnetic field according to claim 1, wherein the bismuth-substituted magnetic garnet single crystal film of at least one type is laminated. The sensor head.