JPS62215836A - Optical wave guide type temperature sensor - Google Patents

Abstract

PURPOSE:To obtain a temperature sensor having high reliability, by providing only one optical guide among two Y-branched optical guides to the area having high electric field intensity of a substrate having pyroelectric effect and electrooptic effect. CONSTITUTION:By surrounding the outer peripheries of a substrate 6 and an insulating film 11a by a metal film 12, charge of inverse polarity is induced in the metal film 12 by the charge generating on the surface of the substrate 6. Therefore, an electric field is generated in the insulating film 11a between the surface of the substrate 6 and the metal film 12. However, in the interrupted part 13 of the metal film 12, the electric field formed by the charge on the surface of the substrate 6 passes through the optical wave guide 9 in the substrate 6 to form an area 7 having high electric field intensity. As mentioned above, only one of two wave guides after Y-branch generates the change in electric field intensity by the change in temperature and a refractive index changes by electrooptic effect. Therefore, by detecting the luminous intensity of light beams emitted from both optical wave guides 9, 10 and synthesized, temperature can be measured.

Description

[Detailed Description of the Invention] [Summary] In order to realize a highly sensitive thermometer, an optical waveguide is provided in the electric field created by the charges generated by the pyroelectric effect, and the electric field strength changes with temperature changes. The refractive index of the optical waveguide in the electric field is changed by using the electric field, another optical waveguide is installed in a region unaffected by the electric field, and the light emitted from both optical waveguides is combined and detected to determine the temperature. To detect.

[Industrial application field]

The present invention relates to an optical waveguide temperature sensor that optically measures temperature by utilizing the fact that the refractive index of a leading waveguide changes with temperature.

[Conventional technology]

FIG. 4 is a diagram showing a conventional light-air waveform temperature sensor. An input path 2 and an output path 3 are formed on the substrate 1, and the input path 2 and the output path 3 are Y-branched into two by two parallel waveguides 4.5.

One true waveguide 4 is slightly longer than the other waveguide 5.

. When linearly polarized light with a stable wavelength is input from the input path 2 by the semiconductor laser LD, it branches into two waveguides 4.5, propagates, is combined in the output path 3, and is emitted. At this time, since the lengths of the waveguides 4 and 5 are different, the light propagating through both waveguides 4.5 has a phase difference and interferes with each other in the output path 3.
It emits light with an intensity corresponding to the phase difference.

Since the refractive index of the waveguides 2...5 changes with temperature changes, the refractive index at a certain temperature TI is 11, and the refractive index at a temperature T2 is
Assuming that the refractive index at is 02, the light propagating through waveguides 4 and 5 has nHj! at temperature T1. 1-j! 2), and has a phase difference of n2 (1l-12) at temperature T2. Therefore, as the refractive index of each waveguide changes due to a temperature change, the light intensity of the output light from the output path 3 changes. By detecting this with a photodiode D or the like, the temperature can be measured.

[Problem that the invention seeks to solve]

Although this change in refractive index with temperature is utilized, this effect is small, so to achieve high sensitivity the element length must be increased, resulting in a large device. The technical problem of the present invention is to eliminate such problems with conventional optical waveguide temperature sensors and realize a small and highly sensitive leading waveform temperature sensor, thereby making it possible to immediately respond to the intelligentization of various devices. It is in.

[Means for solving problems]

FIG. 1 is a sectional view illustrating the basic principle of an optical waveguide temperature sensor according to the present invention. 6 is a substrate having a pyroelectric effect and an electro-optic effect, a charge appears on the surface, and the polarization effect changes with temperature change.

On this substrate 6, a region 7 with a high electric field density and a region 8 with a low electric field density are formed. An optical waveguide 9 is provided in a region 7 where the electric field density is high, and another optical waveguide 10 is formed in a region 8 where the electric field and density are low.

Both optical waveguides 9 and 10 are arranged in parallel, and one end of each is connected to one input path, and the other end is connected to one output path.

[Effect]

Since the leading waveguide 9 is located in a region with high electric field density due to polarized charges generated by the pyroelectric effect of the substrate 6, when the electric field density changes due to temperature change, the refractive index in the leading waveguide 9 changes due to the electro-optic effect. . Since the other leading waveguide 10 is provided in the region 8 where electric field density is low, there is little change in electric field density due to temperature change, and therefore, change in refractive index is also small. Therefore, two leading waveways 9,
When the light that has entered the IO exits from the output path, the refractive index of one of the optical waveguides 9 changes due to temperature change, so that the phase difference between the output lights from both optical waveguides 9 and 10 changes. As a result, by detecting the emitted light with a photoelectric element,
Can measure temperature. Further, since the crystal of the substrate 6 has a large pyroelectric effect and electro-optic effect, a highly sensitive optical waveguide temperature sensor can be realized with a small element.

〔Example〕

Next, how the leading waveform temperature sensor according to the present invention is practically implemented will be explained by way of an example.

FIG. 2 is a sectional view of an optical waveguide temperature sensor according to the present invention, and FIG. 3 is a perspective view of the same temperature sensor. As the substrate 6 having a pyroelectric effect and an electro-optic effect, Z-cut Li
NbO3 is suitable, but LiTa0z (lithium tantalate) and the like are also effective. On this substrate 6, Ti
By thermally diffusing the light at a temperature of about 1000° C., two optical waveguides 9 and 10 are formed in parallel.

On the substrate 6, one end of both optical waveguides 9 and 10 is connected to one input path 2, and the other end is connected to the output path 3, thereby configuring a Matsuhatsu Ender interferometer using a Y branch. ing. In order to form an insulating layer, an insulating film 11a deposited with Sing is formed on the surface on the optical waveguide 9.10 side. A metal film 12 is formed by vapor deposition or the like so as to surround the insulating film 11a and the outer periphery of the substrate 6.
The interrupted portion 13 is formed by masking and depositing only the area facing the leading waveguide 9.

In this way, by surrounding the outer periphery of the substrate 6 and the insulating film 11a with the metal film 12, as shown in FIG. Ru. Therefore, an electric field is generated in the insulating film 11a between the surface of the substrate 6 and the metal film 12.

However, in the interrupted portion 13 of the metal film, the electric field created by the charges on the surface of the substrate 6 passes through the optical waveguide 9 in the substrate 6, as shown in FIG. 1, and a region 7 with high electric field density is formed.

In this way, in only one of the two waveguides after the Y branch, the electric field density changes due to temperature change, and the refractive index changes through the electro-optic effect. Therefore, temperature can be measured by detecting the light intensity of the combined light emitted from both optical waveguides 9 and 10.

〔Effect of the invention〕

As described above, according to the present invention, the two Y-branch optical waveguides 9
．． Among the waveguides 10, only one of the leading waveguides 9 is provided in a region of a substrate having a pyroelectric effect and an electro-optic effect with a high electric field density, so that the pyroelectric effect and the electro-optic effect are large. Therefore, sufficient temperature can be obtained without increasing the size of the substrate 6, and a highly reliable optical waveguide temperature sensor can be realized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view illustrating the basic principle of the leading waveform temperature sensor according to the present invention, FIG. 2 is a cross-sectional view showing an embodiment of the optical waveform temperature sensor according to the present invention, and FIG. 3 is a perspective view of the same embodiment sensor. , FIG. 4 is a plan view of a conventional optical waveguide temperature sensor. In the figure, 6 is a substrate, 7 is a region with high electric field density, 8 is a region with low electric field density, 9 and 10 are optical waveguides, 11 is an insulating layer, 12 is a metal film, and 13 is an interrupted portion. Patent applicant Fujitsu Co., Ltd. Agent Patent attorney Minoru Aoyagi Figure 1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1), a substrate (6) with pyroelectric effect and electro-optic effect,
Region (7) with high electric field density generated from the substrate (6)
and forming a region (8) with a weak electric field; two optical waveguides (9) and (10) are provided on the substrate (6), and one of the optical waveguides (9) is connected to the region with a high electric field density. (7), and the other optical waveguide (10) is placed in the region (10) with low electric field density, and one end of both optical waveguides (9) and (10) are connected to one input path. An optical waveguide temperature sensor characterized in that the other ends thereof are connected to one emission path. (2) A substrate having the above-mentioned pyroelectric effect and electro-optic effect (
An insulating layer (11) is provided on one surface of the substrate (6), a metal film (12) is provided on the outer periphery of the substrate (6) and the insulating layer (11), and an interrupted portion (13) of the metal film is provided on the insulating layer (11). ) The optical waveguide temperature sensor according to claim 1, wherein the electric field density at the position (7) corresponding to the interruption part (13) is increased.