JP2017172993A - Optical detection type hydrogen gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical detection type hydrogen gas sensor with which it is possible to detect a hydrogen gas with high accuracy while protecting a detection element against hydrogen gas explosion.SOLUTION: This optical detection type hydrogen gas sensor includes at least a light source, a polarizer, a detection element, a magnetic field application mechanism, and a photodetector. Light from the light source is radiated to a laminate on condition that a magneto-optical signal is augmented by multiple reflection occurring in the laminate, and magnetization of the laminate is controlled by the magnetic field application mechanism. A change of the optical properties of a hydrogen gas detection layer at this time due to reaction with a hydrogen gas is detected by the photodetector as a magneto-optical signal representing a change of reflected light from the laminate, whereby a hydrogen gas is detected. Since application of electricity to the hydrogen gas detection layer which a hydrogen gas comes in contact with is unnecessary, it is possible to protect the detection element itself against hydrogen gas explosion. Furthermore, it is possible to construct a detection element that suits to the concentration of a hydrogen gas to be detected, by changing the thickness of the hydrogen gas detection layer, making it possible to provide a safe and high-performance optical detection type hydrogen gas sensor.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydrogen gas sensor, and more particularly to a light detection type hydrogen gas sensor using a magneto-optic effect in a laminate including a hydrogen gas detection layer, a metal magnetic layer, a dielectric optical interference layer, and a metal reflection layer.

  In recent years, hydrogen gas, such as fuel cells and hydrogen automobiles, has attracted attention as a next-generation energy source. However, on the other hand, hydrogen gas is highly diffusible, easily leaked, and has a very high risk of explosion if leaked. In order to use hydrogen gas safely, a highly reliable high performance hydrogen gas sensor is indispensable.

As a hydrogen gas sensor for detecting leakage of hydrogen gas, various types of sensors such as a catalytic combustion type, a semiconductor type, a gas heat conduction type, an electrochemical type, and an optical type have been proposed depending on the detection method. (For example, see Non-Patent Document 1)
Of these, the first three are commercially available. The catalytic combustion type sensor detects heat generated by catalytic combustion due to contact with hydrogen as a change in the resistance value of the Pt wire coil. Since an output proportional to the gas concentration can be obtained, it has excellent quantitativeness and is suitable for detecting leaks with a relatively high concentration. Semiconductor sensor is detected by the electrical resistance changes due to the hydrogen reduction of the oxide semiconductor surface such as SnO _2. It is suitable for low concentration detection, and the response time is about several tens of seconds. Further, the gas heat conduction type sensor uses a difference in heat conduction between a target gas and a standard gas (usually air). It utilizes the property that the thermal conductivity of hydrogen gas is very good compared to other combustible gases, and is used for hydrogen detection in a high concentration region.

Here, these hydrogen gas sensors that have been put into practical use generally require a high operating temperature in order to improve response speed, cleaning effect, and the like, and are based on a high temperature operation of about 200 ° C. or higher. In addition, each sensor captures the response of the element as an electrical signal, and there is a risk that an overcurrent or spark in an electrical circuit that comes into contact with hydrogen gas may be a source of ignition.

As a sensor that can avoid the problem of explosion danger due to electrical contact, a light detection type hydrogen gas sensor that detects leakage of hydrogen gas by an optical method has been proposed. (For example, see Patent Documents 1 to 4)

  Patent Documents 1 to 3 disclose a technique for detecting hydrogen gas by irradiating light to a hydrogen gas detection catalyst whose absorbance changes when touched by hydrogen gas and receiving transmitted light or reflected light from the detection catalyst. Has been. Patent Document 4 discloses a technique for detecting Raman scattered light generated from hydrogen gas when laser light is irradiated.

  Furthermore, Non-Patent Document 2 discloses a technique related to a chemical sensor that detects the presence or absence of a surface substance or a change in the refractive index of the sensor surface by utilizing a magneto-optic effect.

Japanese Examined Patent Publication No. 3-67218 JP 2007-71866 A JP 2007-120971 A JP 2011-158307 A

Advanced Chemical Sensor, Part I Gas Sensor, Electrochemical Society / Chemical Sensor Research, TIS Co., Ltd. The 75th JSAP Autumn Meeting, Proceedings, 18p-PA1-14, JSAP

  However, in the above-described photodetection type hydrogen gas sensor that detects transmitted light, reflected light, or Raman scattered light, the detection signal fluctuates due to fluctuations in the output of the light source used to detect hydrogen gas, improving detection accuracy. There is a need for improvement.

  Therefore, the object of the present invention is to solve the above-mentioned problems and to perform high-performance photodetection that can detect hydrogen gas in a wide concentration range and with high accuracy while achieving explosion protection of the detection element itself against hydrogen gas. The object is to provide a hydrogen gas sensor.

  In order to solve the above-described problems, the photodetection type hydrogen gas sensor according to the present invention includes at least a light source, a polarizer, a detection element, a magnetic field application mechanism, and a photodetector. The sensing element may be a laminate in which a metal reflective layer, a metal magnetic layer, a dielectric optical interference layer, and a hydrogen gas detection layer are laminated in this order on the substrate, or a metal reflective layer and a dielectric optical interference layer on the substrate. , A metal magnetic layer, a dielectric optical interference layer, and a hydrogen gas detection layer. And according to the photodetection type hydrogen gas sensor of the present invention, the condition that the magneto-optical signal of the incident light is enhanced by the multiple reflection generated in the laminate when the light emitted from the light source is incident on the laminate. The light is emitted from the light source. At this time, the change in the optical characteristics of the hydrogen gas detection layer accompanying the reaction with the hydrogen gas is a change in the reflected light from the laminate by controlling the magnetization of the metal magnetic layer by the magnetic field application mechanism. Hydrogen gas is detected by measuring with a photodetector as a magneto-optical signal. Since the magneto-optical signal is independent of the intensity of the irradiated light, stable hydrogen gas detection is possible even when the output of the measurement light source fluctuates. Further, by changing the thickness of the hydrogen gas detection layer, a detection element suitable for the concentration of hydrogen gas to be detected can be provided, and a high-performance photodetection type hydrogen gas sensor can be provided.

  In addition, the photodetection type hydrogen gas sensor according to the present invention controls the magnetization of the laminate by using a leakage magnetic field generated by applying an electric current to the metal reflection layer constituting the laminate. It is said. According to such a configuration, it is not necessary to separately provide a magnetic field application mechanism such as an electromagnet for controlling the magnetization of the metal magnetic layer that constitutes the laminated body. Therefore, the configuration of the sensor element is simplified, and the cost and size are reduced. It is possible to provide a photodetection type hydrogen gas sensor.

  Further, the hydrogen gas detection layer constituting the laminate is preferably a palladium (Pd) thin film. According to such a configuration, hydrogen gas can be detected at room temperature, and a heating mechanism is not required. Therefore, there is an effect that hydrogen gas can be detected safely with low power consumption.

  Furthermore, the metal magnetic layer constituting the laminate is preferably a perpendicular magnetization film. According to such a configuration, it becomes easy to miniaturize the laminate constituting the photodetection type hydrogen gas sensor, and by making each detection element suitable for different hydrogen concentrations, hydrogen gas in a wide concentration range can be obtained. The effect is that it can be detected with high accuracy.

  Furthermore, it is preferable that the materials of the metal magnetic layer, the dielectric optical interference layer, and the metal reflective layer constituting the laminate are a CoPt alloy thin film, a ZnO thin film, and an Ag thin film, respectively. According to this configuration, it is possible to greatly enhance the magneto-optical signal due to the multiple reflection generated in the laminate, and it is possible to detect the leakage of hydrogen gas with high sensitivity.

  The photodetection-type hydrogen gas sensor according to the present invention includes at least a light source, a polarizer, a detection element, a magnetic field application mechanism, and a photodetector, and further, when light emitted from the light source enters the laminate. Irradiating light from the light source under the condition that the magneto-optical signal of the incident light is enhanced by the multiple reflection generated in the laminate, and optical such as refractive index or absorption coefficient accompanying the reaction with the hydrogen gas of the hydrogen gas detection layer Hydrogen gas is detected by measuring a change in reflected light from the laminate due to a characteristic change by the photodetector as a magneto-optical signal by controlling the magnetization of the metal magnetic layer by the magnetic field application mechanism. To do. Therefore, in the photodetection type hydrogen gas sensor according to the present invention, it is not necessary to apply electricity to the hydrogen gas detection layer that is actually in contact with the hydrogen gas. Since the magneto-optical signal is independent of the intensity of the irradiated light, stable detection of hydrogen gas is possible even when the output of the light source used for detection of hydrogen gas fluctuates. Further, by changing the thickness of the hydrogen gas detection layer, a detection element suitable for the concentration of hydrogen gas to be detected can be provided. This makes it possible to provide a safe and high-performance photodetection type hydrogen gas sensor.

It is a block diagram which shows typically the optical detection type hydrogen gas sensor of 1st Embodiment. It is a block diagram which shows typically the other optical detection type hydrogen gas sensor of 1st Embodiment. It is explanatory drawing which shows the magneto-optical characteristic of the detection element which comprises the light detection type hydrogen gas sensor shown in FIG. 1, FIG. 2, and the detection principle of hydrogen gas. It is a block diagram which shows typically the optical detection type hydrogen gas sensor of 2nd Embodiment. It is sectional drawing which shows typically the detection element which comprises the light detection type hydrogen gas sensor of Example 1. FIG. Sectional drawing which shows typically the detection element which comprises the light detection type hydrogen gas sensor of Example 2. FIG. It is a figure explaining the effect of Example 1 and Example 2. FIG. FIG. 7 is a characteristic diagram showing detection of hydrogen gas by the detection element shown in FIGS. 5 and 6.

  In the photodetection type hydrogen gas sensor of the present invention, when light is irradiated to a detection element composed of a laminate including a hydrogen gas detection layer, a metal magnetic layer, a dielectric optical interference layer, and a metal reflection layer, Hydrogen gas is detected by utilizing the enhancement effect of the magneto-optical signal by multiple reflection. Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
1 and 2 are configuration diagrams schematically showing a photodetection type hydrogen gas sensor 10 according to a first embodiment of the present invention. The photo-detecting hydrogen gas sensor 10 is based on a normal incidence optical system, and irradiates light from the vertical direction to the detection surface of the laminated body 13 that functions as a detection element as shown in FIGS. Detect hydrogen gas. In the present embodiment, the light detection type hydrogen gas sensor 10 includes a light source 11 for irradiating the laminated body 13 with linearly polarized light, a magnetic field applying mechanism 19 for applying a magnetic field to the laminated body 13, and the laminated body 13. A light splitter 12 for guiding the reflected light to the light detector 21, a polarizer 20 for detecting a change in the polarization angle of the reflected light due to the magneto-optical effect in the laminate 13, and the light transmitted through the polarizer 20 It comprises a photodetector 21 for detecting a change in the intensity of the reflected light.

  As the light source 11 for irradiating linearly polarized light, a monochromatic light source that emits light of a single wavelength, such as a semiconductor laser or a gas laser, is used, and in particular, linearly polarized light using a polarizer such as a Glan-Thompson prism. It is preferable to improve the characteristics. The magnetic field application mechanism 19 controls the magnetization of the metal magnetic layer 16 constituting the multilayer body 13 by applying a magnetic field to the multilayer body 13 by passing an electric current through a coil.

  As shown in FIG. 1, the laminate 13 is a structure in which a metal reflection layer 18, a dielectric optical interference layer 17, a metal magnetic layer 16, and a hydrogen gas detection layer 14 are laminated in this order, or as shown in FIG. The metal reflective layer 18, the dielectric optical interference layer 17, the metal magnetic layer 16, the dielectric optical interference layer 15, and the hydrogen gas detection layer 14 are configured in this order, and the hydrogen gas of the hydrogen gas detection layer 14 is formed. Hydrogen gas is detected by measuring a magneto-optical signal that is a change in reflected light due to a change in optical characteristics such as a refractive index or an absorption coefficient associated with the reaction. Here, the dielectric optical interference layers 15 and 17 need to have such a thickness that the light applied to the multilayer body 13 causes multiple reflection inside the multilayer body 13. Specifically, the hydrogen gas detection layer It is preferable that the value obtained by multiplying the thickness of each of 14, the metal magnetic layer 16, and the dielectric optical interference layers 15 and 17 by the refractive index is thicker than about ¼ of the wavelength of light to be irradiated. Furthermore, the hydrogen gas detection layer 14 and the metal magnetic layer 16 need to have a thickness that allows the light irradiated on the multilayer body 13 to enter the multilayer body 13. Specifically, the thickness is 30 nm or less. It is preferable that In addition, the metal reflection layer 18 needs to have a thickness sufficient to reflect light that has entered the laminated body 13, and specifically, the thickness is preferably 50 nm or more.

  As the material used for the hydrogen gas detection layer 14, any material can be used as long as the optical properties such as the refractive index and the absorption coefficient change in accordance with the reaction with the hydrogen gas. It is preferable to use Pd, which has a large optical change due to contact with Pd. Further, in this case, since Pd has absorption and emission characteristics of hydrogen gas at room temperature, it is possible to provide a hydrogen gas sensor capable of operating at room temperature. Play.

  Examples of the material used for the metal magnetic layer 16 include general magnetic materials made of metals such as Fe, Co, and Ni, alloys, and the like. In particular, CoPt alloy films, FePt alloy films, Co / Pd multilayer films, Co A perpendicular magnetization film such as a / Pt multilayer film is preferable. In this case, compared to the in-plane magnetization film, it is easy to produce a plurality of sensing elements by microfabrication from the viewpoint of magnetization stability. Therefore, it is possible to provide a hydrogen gas sensor capable of detecting hydrogen gas over a wide concentration range by providing each detection element with a structure suitable for the detection concentration.

Examples of the material used for the dielectric optical interference layers 15 and 17 include general transparent oxides or transparent nitrides such as SiO ₂ , ZnO, MgO, TiO ₂ , and AlN, and the wavelength of light emitted from the light source 11. On the other hand, it is preferable to have a high transmittance. Moreover, as a material used for the metal reflection layer 18, a general metal material made of a metal such as Ag, Al, Au, or Cu, an alloy, or the like can be given. It preferably has a reflectance.
[Example]

  FIG. 5 is a cross-sectional view schematically showing the detection element 50 constituting the photodetection type hydrogen gas sensor according to Example 1 of the present embodiment.

  In the detection element 50 according to the first embodiment, a base layer 57 made of a ZnO thin film having a thickness of 10 nm is formed on a glass substrate 58, and a stacked body 51 that actually detects hydrogen gas is formed thereon. . The laminated body 51 includes an Ag thin film having a thickness of 100 nm as the metal reflective layer 56, a ZnO thin film having a thickness of 70 nm as the dielectric optical interference layer 55, a CoPt alloy thin film having a thickness of 2.8 nm as the metal magnetic layer 54, and The hydrogen gas detection layer 52 is composed of a structure in which Pd thin films having a thickness of 2.4 nm are stacked in this order.

  FIG. 6 is a cross-sectional view schematically showing a detection element 60 that constitutes the light detection type hydrogen gas sensor according to Example 2 of the present embodiment.

  In the detection element 60 of the second embodiment, a base layer 67 made of a ZnO thin film having a thickness of 10 nm is formed on a glass substrate 68, and a stacked body 61 that actually detects hydrogen gas is formed thereon. . The laminated body 61 includes a Ag thin film having a thickness of 100 nm as the metal reflective layer 66, a ZnO thin film having a thickness of 38 nm as the dielectric optical interference layer 65, a CoPt alloy thin film having a thickness of 2.8 nm as the metal magnetic layer 64, a dielectric The body interference layer 63 includes a ZnO thin film having a thickness of 38 nm, and the hydrogen gas detection layer 62 includes a structure in which a Pd thin film having a thickness of 3.2 nm is stacked in this order. That is, in Example 1 shown in FIG. 5, the base of the hydrogen gas detection layer 62 is a metal magnetic layer, whereas in Example 2 shown in FIG. 6, the base of the hydrogen gas detection layer 62 is a dielectric interference layer. The point is the difference.

  Actually, the results of detecting a mixed gas of nitrogen and 4% hydrogen using the sensing element 60 and the sensing element 50 are shown in FIGS. 7A and 7B, respectively. In each graph, the left side is the result when nitrogen is detected, and the right side is the result when 4% hydrogen mixed gas is detected. In any of the embodiments, reflection from the detection element 60 and the detection element 50 when a mixed gas of pure nitrogen gas, nitrogen, and hydrogen is alternately flowed with a periodically changing magnetic field applied to the detection element. The change in the polarization angle of the emitted light was measured. As a light source for detecting hydrogen gas, a semiconductor laser having a wavelength of 658 nm was used, and linearly polarized light was applied to the detection elements 60 and 50 by transmitting the polarizer. As the periodically changing magnetic field, in the case of the above-described first embodiment, a magnetic field of about −1 kOe (downward direction in FIG. 5) to 1 kOe (upward direction in FIG. 5) is applied, and in the case of the second embodiment, A magnetic field of about −1.5 kOe (downward direction in FIG. 6) to 1.5 kOe (upward direction in FIG. 6) was applied.

As shown in FIG. 7, as described in the first embodiment, the hydrogen gas detection layers 62 and 52 react with the hydrogen gas, so that the conditions of the multiple reflections in the stacked bodies 61 and 51 change, respectively. As can be seen, the polarization angle of the light reflected from the sensing elements 60 and 50 changes. Thus, in both Examples 1 and 2, changes in the deflection angle of light due to hydrogen gas were confirmed. Here, in the sensing element 60 of Example 2 shown in FIG. 7A, the light deflection angle changed by 12% before and after the hydrogen gas reaction, whereas in Example 1 shown in FIG. 7B. In the detection element 50, the change is 5% before and after the hydrogen gas reaction. Therefore, the structure of the second embodiment can obtain a light deflection angle that is twice or more larger. According to the experiments by the present inventors, it was confirmed that the sensitivity of the hydrogen gas sensor has a maximum value with respect to the thickness of the hydrogen gas detection layer. For example, in Example 1, the film thickness of the hydrogen gas detection layer is about 1 nm to 3 nm, and in Example 2, the film thickness of the hydrogen gas detection layer is about 3 nm to 6 nm and has a maximum value. That is, in Example 1, the thickness of the hydrogen gas detection layer needs to be reduced to about 1 nm to 3 nm, whereas in Example 2, it may be about 3 nm to 6 nm. It becomes possible to detect gas.

FIG. 8 shows the results when a mixed gas of nitrogen and 4% hydrogen is detected in time series with respect to the detection element 60 of the second embodiment. Here, the measurement conditions are the same as those described above with reference to FIG. By measuring this change in the polarization angle as a change in the intensity of light transmitted through the polarizer with a photodetector, it is possible to detect hydrogen gas with high accuracy.

  Next, the detection principle of the hydrogen gas by the light detection type hydrogen gas sensor 10 of the present embodiment will be described with reference to FIG.

Here, the laminate 13 constituting the sensing element, when the wavelength is irradiated with light of lambda ₁ of the linearly polarized light by multiple reflection in the interior of the laminate 13, is the largest polarization angle of light reflected Consider the case where

In the laminated body 13 having the above-described configuration, linearly polarized light is applied in a state where a magnetic field (+ H ₁ or −H ₁ ) having a predetermined intensity capable of setting the magnetization of the metal magnetic layer 16 in one direction is applied by the magnetic field applying mechanism 19. As shown in FIG. 3A, the irradiated light is subjected to a large magneto-optical effect due to multiple reflection inside the laminate 13, and as a result, a large polarization angle (+ θ _K1 or −θ _K1). ) Is emitted. Next, as shown in FIG. 3B, when hydrogen gas is in contact with the hydrogen gas detection layer 14 in a state where a magnetic field (+ H ₁ or −H ₁ ) is applied, the refractive index or absorption of the hydrogen gas detection layer. When the optical characteristics such as the coefficient change, the light interference condition in the laminate 13 changes, so that the influence of multiple reflection is reduced. As a result, the magnitude of the polarization angle of the emitted light (| θ _K2 |) Is smaller than the initial state without hydrogen gas (| θ _K1 |> | θ _K2 |). Since the polarization angle of the light reflected from the laminated body 13 changes depending on the direction of magnetization of the metal magnetic layer 16 constituting the laminated body 13, the magneto-optic curves are respectively shown in FIG. (D).

Therefore, the magnetic field application mechanism 19 applies a magnetic field (± H ₁ ) that periodically changes at a predetermined intensity to the stacked body 13, thereby determining the presence or absence of hydrogen gas and the polarization angle of the light reflected from the stacked body 13. By detecting a magneto-optical signal that is a change, hydrogen gas can be detected with high accuracy.

  Specifically, the light reflected from the stacked body 13 is guided in the direction of the photodetector 21 by the light splitter 12. At this time, by arranging the polarizer 20 set at a predetermined detection angle in front of the photodetector 21, the intensity of light transmitted through the polarizer 20 is equal to the polarization angle of the light reflected from the laminate 13. Accordingly, a magneto-optical signal, which is a change in polarization angle, can be detected by the photodetector 19 as a change in light intensity.

  In the light detection type hydrogen gas sensor as described above, it is effective to use a differential detection method generally known in a magneto-optical recording system as one method for improving detection accuracy. In this case, a polarizing beam splitter is used instead of the polarizer 20. The light reflected from the stacked body 13 is split into two lights, p-polarized light and s-polarized light, by passing through the polarization beam splitter. Each of the divided lights is detected by two photodetectors, and a magneto-optical signal is detected by taking a difference in the intensity of the light detected by each photodetector. In this method, in particular, detection with low noise is possible for fluctuations in the intensity of light emitted from the light source, and hydrogen gas can be detected with high accuracy.

  Further, the magneto-optical signal detected by the photodetector 21 is detected in synchronization with the magnetic field applied to the stacked body 13 by the magnetic field applying mechanism 19. Therefore, performing synchronous detection or Fourier analysis using a magnetic field that periodically changes by passing a current through the coil is effective in improving detection sensitivity by reducing noise in the magneto-optical signal.

  In the present embodiment, the case where hydrogen gas is detected by detecting the decrease in the polarization angle has been described, but the present invention is not limited to this. By adjusting the thickness of each layer constituting the laminated body 13 or selecting a material, it is possible to set a condition in which the polarization angle increases with the reaction of the hydrogen gas detection layer 14 with hydrogen gas.

[Second Embodiment]
FIG. 4 is a configuration diagram schematically showing a photodetection type hydrogen gas sensor 30 according to the second embodiment of the present invention. Similar to the first embodiment, the photodetection-type hydrogen gas sensor 30 is based on a normal incidence optical system, and irradiates light from the vertical direction to the detection surface of the stacked body 13 that functions as a detection element. Detect gas. In the present embodiment, the light detection type hydrogen gas sensor 30 includes a light source 11 for irradiating the laminate 13 with linearly polarized light, and an AC power supply 31 for applying an AC current to the metal reflection layer constituting the laminate 13. A light splitter 12 for guiding the light reflected from the laminate 13 to the photodetector 21, and a polarizer 20 for detecting a change in the polarization angle of the reflected light due to the magneto-optical effect in the laminate 13; And a photodetector 21 for detecting a change in the intensity of the reflected light transmitted through the polarizer 20.

Here, the photodetection type hydrogen gas sensor 30 of the present embodiment is the first except that it includes an AC power supply 31 that applies an AC current to the metal reflection layer 18 as a magnetic field application mechanism for applying a magnetic field to the stacked body 13. The structure of the laminated body 13 and the material and thickness of each layer constituting the laminated body 13 are the same as in the first embodiment for the same reason as in the first embodiment. It is preferable that However, the metal magnetic layer 16 preferably uses Fe instead of the CoPt alloy. The film thickness of Fe may be the same as the film thickness of the CoPt alloy thin film of the first embodiment.

  As in the case of the first embodiment, the detection element of the light detection type hydrogen gas sensor 20 of the present embodiment includes the metal reflection layer 18, the dielectric light interference layer 17, the metal magnetic layer 16, and the dielectric light interference layer 15. The hydrogen gas detection layer 14 is laminated in this order, and is constituted by the laminated body 13, and a change in the optical characteristics of the hydrogen gas detection layer 14 due to the contact of hydrogen gas is detected as a magneto-optical signal that is a change in reflected light. To detect hydrogen gas. Further, the laminated body 13 is not limited to the configuration described above, and may be a laminate in which the metal reflection layer 18, the dielectric optical interference layer 17, the metal magnetic layer 16, and the hydrogen gas detection layer 14 are laminated in this order.

  At this time, the magneto-optical signal detected by the photodetector 21 is detected in synchronization with the alternating current applied to the metal reflection layer 18 by the alternating current power supply 31. The alternating current is preferably about several mA. Therefore, performing synchronous detection or Fourier analysis is effective in improving detection sensitivity by reducing noise in the magneto-optical signal, as in the first embodiment.

  Further, differential detection using two spectroscopic detectors can reduce noise of the magneto-optical signal as in the case of the first embodiment, and is effective in improving detection sensitivity.

  As mentioned above, although this invention was demonstrated based on 1st, 2nd embodiment and an Example, this invention is not limited to these. For example, the direction of the magnetic field applied to the laminate by the magnetic field application mechanism is set to be perpendicular to the surface of the laminate that detects hydrogen gas, but is not limited thereto. In this case, Fe, Co, Ni having an axis of easy magnetization in the in-plane direction, or an alloy thereof is used as the metal magnetic layer constituting the laminate. Is preferred. Further, the present invention has been described based on a normal incidence optical system. However, the present invention is not limited to this, and the laminated body may be used as long as the light applied to the laminated body is a condition in which the magneto-optical signal is enhanced by multiple reflection. It is also possible to irradiate light from an oblique direction to the detection surface. Furthermore, as a method for irradiating the laminated body with light from the light source and guiding the reflected light from the laminated body to the photodetector, it is also possible to use an optical fiber reflective probe composed of a plurality of optical probes.

  The photodetection type hydrogen gas sensor according to the present invention can be used as a hydrogen gas sensor for detecting leakage of hydrogen gas.

  DESCRIPTION OF SYMBOLS 10, 30 Light detection type hydrogen gas sensor, 11 ... Light source, 12 ... Light splitter, 13, 51, 61 ... Laminated body, 14, 52, 62 ... Hydrogen gas detection layer, 15, 17 55, 63, 65 ... Dielectric optical interference layer, 16, 54, 64 ... Metal magnetic layer, 18, 56, 66 ... Metal reflective layer, 19 ... Magnetic field application mechanism, 20 ... -Polarizer, 21 ... photodetector, 31 ... alternating current power supply, 50, 60 ... sensing element, 57, 67 ... underlayer, 58, 68 ... glass substrate.

Claims (9)

At least a light source, a detection element composed of a laminate including a hydrogen gas detection layer, a metal magnetic layer, a dielectric optical interference layer, and a metal reflection layer, a magnetic field application mechanism, and a photodetector;
When the light emitted from the light source is incident on the sensing element, the light is emitted from the light source under the condition that the magneto-optical signal of the incident light is enhanced by the multiple reflection generated in the laminate, and the magnetic field application mechanism By controlling the magnetization of the stacked body, the optical detector detects a magneto-optical signal that is a change in reflected light from the stacked body due to a change in optical properties due to a reaction with the hydrogen gas of the hydrogen gas detection layer. A photodetection type hydrogen gas sensor characterized by detecting hydrogen gas.   The laminate is a laminate in which a metal reflective layer, a dielectric optical interference layer, a metal magnetic layer, a dielectric optical interference layer, and a hydrogen gas detection layer are sequentially laminated on a substrate. 1. A light detection type hydrogen gas sensor according to 1.   2. The light detection according to claim 1, wherein the stacked body is a stacked body in which a metal reflection layer, a dielectric optical interference layer, a metal magnetic layer, and a hydrogen gas detection layer are stacked in this order on a substrate. Type hydrogen gas sensor.   2. The magnetic field application mechanism according to claim 1, wherein the magnetization of the metal magnetic layer constituting the stacked body is controlled by applying an alternating current to the metal reflective layer constituting the sensing element. 3. Light detection type hydrogen gas sensor.   The light detection type hydrogen gas sensor according to claim 1, wherein the hydrogen gas detection layer constituting the laminate is a palladium thin film.   The photodetection type hydrogen gas sensor according to claim 1, wherein the metal magnetic layer constituting the laminated body is a perpendicular magnetization film.   The photodetective hydrogen gas sensor according to claim 6, wherein the metal magnetic layer constituting the laminate is an alloy thin film of cobalt and platinum.   The photodetection type hydrogen gas sensor according to claim 1, wherein the dielectric optical interference layer constituting the laminate is a zinc oxide thin film.   The photodetection type hydrogen gas sensor according to claim 1, wherein the metal reflection layer constituting the laminate is a silver thin film.

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