JPH0784295A - Method for producing organic single crystal core fiber - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for producing an organic single crystal core fiber which is used in a fiber type optical wavelength conversion element and which can improve the conversion efficiency of the second harmonic and increase the output of the second harmonic. To do. In the method for producing an organic single crystal core fiber in which an organic nonlinear optical material such as 3,5-dimethyl-1 (4-nitrophenyl) pyrazole is filled in a glass capillary, a decomposition temperature equal to or higher than a melting point of the organic nonlinear optical material is used. The organic non-linear optical material has a viscosity of 1 when heated to the temperature below.
A method for producing an organic single crystal core fiber, which comprises the step of filling the inside of a glass capillary with an organic nonlinear optical material while controlling it to 0 poise or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an organic single crystal core fiber used in a fiber type optical wavelength conversion device.

[0002]

2. Description of the Related Art It is called a linear optical response of a substance that electrical polarization induced in a substance by a strong photoelectric field such as that obtained by laser light is proportional to the photoelectric field. Is proportional to the square, cube, ... Of the non-linear optical response, and various effects resulting from such non-linear optical response are generically called non-linear optical effects.

The optical wavelength conversion device refers to a laser light source utilizing this so-called nonlinear optical effect. According to this device, coherent light having a frequency twice that of the fundamental wave laser light and having the same properties as the laser light of the fundamental wave light source can be easily extracted,
Its application is expected in a wide range of fields such as information recording, image processing, and laser measurement. Further, in the optical wavelength conversion element that constitutes such an optical wavelength conversion device, even if the nonlinearity of the substance exhibiting the nonlinear optical effect is small, if the interaction length can be made long, or a high output fundamental wave light source is used. In principle, using a laser
It is also possible to obtain a conversion efficiency close to%. For example, by using a semiconductor laser having an output level of several mW to several hundred mW as a fundamental wave light source, it is possible to realize a small-sized and simple low-cost visible coherent light source by wavelength conversion.

As the light wavelength conversion element constituting the conventional light wavelength conversion device, LiNbO ₃ (LN), KTiOPO is used.
₄ (KTP), KH ₂ PO ₄ (KDP), NH ₄ H ₂ PO ₄
(ADP) or other inorganic crystal and a resonator type optical wavelength conversion element basically consisting of several mirrors, slab type or ridge type on the same inorganic crystal substrate by proton exchange or titanium diffusion method. A waveguide-type optical wavelength conversion element formed with a waveguide, or a domain inversion layer is provided on the waveguide of the waveguide-type optical wavelength conversion element by an electron beam drawing method to satisfy the pseudo phase matching condition. There is a quasi-phase matching type optical wavelength conversion element having a variable structure.

However, in the light wavelength conversion element using an inorganic crystal, a single crystal having a high optical purity is very expensive, some crystals show deliquescence and are inconvenient to handle, and the optical damage strength is poor. And the problems of the nonlinear optical crystal itself, such as the fact that the second-order nonlinear susceptibility is not high,
Further, for example, when a waveguide type element is configured, there is a problem that the operating conditions such as temperature tolerance and wavelength tolerance for generating the second harmonic become extremely strict. In particular, in the resonator type optical wavelength conversion element, a crystal as a laser medium such as YAG or YVO ₄ is further required in addition to the nonlinear optical crystal, which is very expensive or cannot be directly modulated. There is a problem that it is not suitable for recording applications.

On the other hand, as a non-linear optical crystal replacing the inorganic crystal, for example, 2-methyl-4-nitroaniline (MN) is used.
A), an organic crystal such as 4- (N, N-dimethylamino) -3-acetamidonitrobenzene (DAN), chalcone and the like have also been attempted to be made into a device. Among the optical wavelength conversion elements using these organic crystals, the large nonlinear optical characteristics of the organic nonlinear optical material can be effectively used, and the tolerance to temperature and wavelength is comparatively large, so that it can be applied to consumer equipment. From the point of view, a fiber-type optical wavelength conversion element is currently very promising.
This fiber-type optical wavelength conversion element has a structure in which an organic crystal having nonlinear optical characteristics is filled and crystallized in a capillary of a fiber, and currently, research and development are actively conducted to realize the element. .

Further, as a method for producing an organic single crystal core fiber used in a fiber type optical wavelength conversion element,
First, in a closed system, a glass capillary with its opening facing downward is immersed in a melt of an organic nonlinear optical material that has been heated up to about the melting point, and the entire system is depressurized to reduce the inert gas such as Ar. The organic non-linear optical material is filled into the glass capillary by breaking the vacuum with a gas. Next, the glass capillary filled with the organic nonlinear optical material is gradually cooled to crystallize the organic nonlinear optical material (JP-A-63-63).
50400 gazette etc.).

Then, the glass capillary is cut with a fiber cutter or a ruby cutter at a necessary portion to produce an organic single crystal core fiber.

[0009]

However, in the above-mentioned conventional method for manufacturing an organic single crystal core fiber, when the organic nonlinear optical material is filled in the glass capillary, the organic nonlinear optical material is heated up to about the melting point. Therefore, the melt has a high viscosity of about 20 to 40 poise, and the filling into the glass capillary is
It was extremely inefficient because it was greatly decompressed and this process required a long time.

In the above-mentioned conventional method for producing an organic single crystal core fiber, since the glass capillary filled with the organic nonlinear optical material and crystallized is cut by a cutter such as a fiber cutter or a ruby cutter, However, the cut end surface could only have irregular unevenness and poor smoothness. Therefore, when the organic single crystal core fiber whose end face is cut as in the conventional case is used for the fiber-type optical wavelength conversion element, the second harmonic is scattered at the end face of the fiber, which makes it difficult to collect the light. This has been a cause of remarkably reducing the output of the second harmonic.

The present invention has been made to solve the above problems, and is used in a fiber type optical wavelength conversion element, and the conversion efficiency of the second harmonic is improved and the second harmonic is increased. It is an object of the present invention to provide a method for producing an organic single crystal core fiber that can be output.

[0012]

In order to solve the above problems, the present invention provides a method for producing an organic single crystal core fiber in which a glass capillary is filled with an organic nonlinear optical material, wherein the organic nonlinear optical material has a melting point not lower than its melting point. The method includes a step of heating the organic non-linear optical material to a temperature equal to or lower than the decomposition temperature and controlling the viscosity of the organic non-linear optical material to 10 poise or less to fill the inside of the glass capillary with the organic non-linear optical material.

Further, the present invention includes a step of processing the end face of the organic single crystal core fiber with a dicing saw in the method of manufacturing the organic single crystal core fiber in which the organic nonlinear optical material is filled inside the glass capillary.

[0014]

According to the method for producing an organic single crystal core fiber of the present invention, since the step of filling the glass capillary with the organic nonlinear optical material as described above is included, this step can be efficiently performed in a short time. it can.

In the method for producing an organic single crystal core fiber of the present invention, the dicing saw used for processing the end face of the organic single crystal core fiber is called a blade in which diamond is embedded in a material such as metal or synthetic resin. For thin disks, 10,000 to 70,000 rpm
The cutting and end face processing are performed by rotating at high speed at the number of revolutions. Therefore, in the present invention, the process of using this dicing saw is included in the end face processing of the organic single crystal core fiber, so that the smoothness of the cut end face can be improved much more than in the conventional case.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a glass capillary 1 used for manufacturing an organic single crystal core fiber according to the present invention. In this embodiment, as shown in FIG.
The main body 2 is a hollow cylindrical glass capillary having a hollow cylindrical portion 3 and a substantially spherical front spherical portion 4 serving as a condenser lens, and having an outer diameter of 1 mm and an inner diameter of 1.3 μm. However, the present invention is not limited to this, and a hollow cylindrical ordinary glass capillary may be used, and the outer diameter, the inner diameter, and the like are not limited to those in this embodiment.

Next, the filling of the organic nonlinear optical material into the glass capillary shown in FIG. 1 will be described. First, in a closed system, the opening end surface of the glass capillary opposite to the tip spherical portion is immersed in the melt in which the organic nonlinear optical material is heated and held in the melt state, and the whole system is depressurized. ,
The organic nonlinear optical material was filled into the glass capillary by injecting Ar gas to bring the entire system to an atmospheric pressure. Here, in this example, 3,5-dimethyl-1 (4-nitrophenyl) was used as the organic nonlinear optical material.
Pyrazole was used. And 3,5-dimethyl-1
Since the melting point of (4-nitrophenyl) pyrazole was 103 ° C and the decomposition temperature was about 200 ° C, it was about 10
By heating to 6 ° C., this viscosity can be controlled to about 2.5 poise, and in this state, the glass capillary was filled with the organic nonlinear optical material as described above. As a result, the viscosity was controlled to be lower than in the conventional case, so that this filling step could be performed efficiently in a short time.

In this example, 3,5-dimethyl-1 (4-nitrophenyl) was used as the organic nonlinear optical material.
Pyrazole was used, but the material is not limited to this, and other organic nonlinear optical materials may be used,
It is desirable to have a large non-linear optical characteristic. Further, the heating temperature is not limited to the above-mentioned examples, and can be appropriately set as long as it is a temperature above the melting point and below the decomposition temperature of the organic nonlinear optical material used and its viscosity can be controlled below 10 poise.

Next, the glass capillary filled with the organic nonlinear optical material as described above was passed through a Bridgman furnace to grow crystals of the filled organic nonlinear optical material core material.

Next, the end face processing of the organic crystal core fiber according to the present invention will be described. As shown in FIG. 2, the organic single crystal core fiber 5 obtained by filling the glass capillary with the organic nonlinear optical material and crystallizing the organic single crystal core fiber 5 as described above is applied to the jig 6 by using the baking plate 7a and the baking material 7b. After fixing, the end face was processed at the cutting line 8 with a dicing saw. As the conditions for the end surface processing in this embodiment, no pasting wax was used, the material of the blade was resin, the roughness was No. 600, and the rotation speed was 3
The end face processing was performed at 0000 rpm.
The present invention is not limited to this embodiment.

In this example, a cross-section of an organic single crystal core fiber having an end face processed was observed with an optical microscope, and a 50 × micrograph is shown in FIG. 3 (A).
Comparing this with the micrograph of 50 times the cross section cut by the ruby cutter shown in FIG. 3 (B), the smoothness of the end surface by the end surface processing according to the present invention is clearly much higher than that by the ruby cutter. It turns out that it is a good one.

Next, an operation experiment using the organic single crystal core fiber produced as described above will be described. When a laser beam emitted from a semiconductor laser having an oscillation wavelength of 870 nm, which is a fundamental wave generating means, is incident on the front spherical portion of the organic single crystal core fiber, the laser light is directed to the core made of the organic nonlinear optical material by the front spherical portion. The light was condensed and the second harmonic could be generated. Here, it is possible to extract only the second harmonic by separating or absorbing it by a deflecting beam splitter, an IR absorption filter, or the like.

FIG. 4 shows the result of the spectral analysis of the second harmonic generated in this way. In FIG. 4, the horizontal axis represents wavelength and the vertical axis represents light intensity. As a result, 435, which is half of the wavelength of the fundamental wave, 870 nm, is obtained.
It can be seen that the second harmonic of nm is generated. Further, since the output side end surface of the organic single crystal core fiber has good smoothness, it is possible to prevent the scattering of the second harmonic wave at this end surface, and it becomes easy to collect the second harmonic wave, The intensity of the second harmonic was stronger than that of the conventional one.

[0024]

As described above, according to the method for producing an organic single crystal core fiber of the present invention described in claim 1, in the step of filling the glass capillary with the organic nonlinear optical material, as compared with the conventional method, It is possible to reduce time and improve efficiency. Therefore, if the manufacturing process of the organic single crystal core fiber is shortened and the organic single crystal core fiber according to the present invention is used for the light wavelength conversion element, the cost of the element can be reduced.

Further, according to the method for producing an organic single crystal core fiber of the present invention as set forth in claim 2, in the step of processing the end face of the organic single crystal core fiber, the smoothness of the end face is far better than in the conventional case. It is possible to improve. Therefore, when the organic single crystal core fiber according to the present invention is used for the light wavelength conversion element, it is possible to prevent the scattering of the second harmonic on the emission surface, and thus it is possible to realize a high performance light wavelength conversion element.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a glass capillary used for manufacturing an organic single crystal core fiber according to an example of the present invention.

FIG. 2 is a perspective view of a jig for fixing the organic single crystal core fiber used in the end face processing step of the organic single crystal core fiber according to the present embodiment.

FIG. 3 (A) is a micrograph of a cross section of the organic single crystal core fiber according to the present example, which is subjected to end face processing,
(B) is a micrograph of a cross section cut by a conventional ruby cutter.

FIG. 4 is a diagram showing a result of spectroscopic spectrum analysis of the light wavelength conversion element of the present embodiment.

[Explanation of symbols]

 1 Glass capillary 5 Organic single crystal core fiber

Claims (2)

[Claims] 1. A method for producing an organic single crystal core fiber in which a glass capillary is filled with an organic nonlinear optical material, wherein the organic nonlinear optical material is heated to a temperature not lower than a melting point and not higher than a decomposition temperature of the material. The viscosity of the optical material is 10
A method for producing an organic single crystal core fiber, which comprises a step of filling an organic nonlinear optical material into the inside of a glass capillary while controlling the poise or less. 2. A method for manufacturing an organic single crystal core fiber in which a glass capillary is filled with an organic nonlinear optical material, comprising a step of processing an end face of the organic single crystal core fiber with a dicing saw. Crystal core fiber manufacturing method.