Light sensor, light detection device, and terahertz / infrared fourier spectroscope

Abstract

This light sensor comprises: a vibration input unit that generates vibrations on the basis of an input signal; a vibration unit that is formed using a MEMS structure using a silicon material, that vibrates on the basis of vibrations transmitted by the vibration input unit, and that includes a both-end supported beam the resonant frequency of which changes due to the input of light; and a vibration detection unit that detects the vibrations of the both-end supported beam.

Description

Optical sensor, optical detection device, and terahertz / infrared Fourier spectrometer

[0001] The present invention relates to an optical sensor, an optical detection device, and a terahertz / infrared Fourier spectrometer for detecting broadband light. This application claims priority to Japanese Patent Application No. 2022-087832, filed on May 30, 2022, the contents of which are incorporated herein by reference.

[0002] Optical sensors are used everywhere in our daily lives, such as in various remote controls, and have become an indispensable part of our lives. These optical sensors are classified into photoelectric and thermal effect types, of which pyroelectric detectors and bolometers are widely used as thermal effect sensors. The bolometer described above has a light-absorbing part that receives light and a detection part that detects temperature changes in the light-absorbing part. The light energy received by the light-absorbing part is converted into thermal energy, and the detection part detects the resistance value of a thermistor, which changes in response to temperature rise.

[0003] Conventional bolometers require cooling of the element and long-term heat integration to achieve high sensitivity. This makes it difficult for conventional bolometers to simultaneously achieve the performance of "room temperature operation," "high speed," and "high sensitivity." To achieve the performance of "room temperature operation," "high sensitivity," and "high speed" in a bolometer, it is necessary to use a physical quantity other than the usual resistance value as the signal.

[0004] In recent years, research has been conducted on elements called MEMS (Micro Electro Mechanical Systems), which are formed using semiconductor microfabrication technology and have microstructures that realize mechanical operations. For example, Patent Document 1 and Non-Patent Document 1 describe highly sensitive bolometer-type optical sensors configured using MEMS.

[0005] The optical sensor described in Patent Document 1 and Non-Patent Document 1 includes a doubly-supported beam formed using MEMS made of GaAs (gallium arsenide) based on semiconductor microfabrication technology, a vibration input unit that inputs vibration to the doubly-supported beam, and a vibration detection unit that detects the vibration of the doubly-supported beam. This optical sensor detects the sensitive change in resonant frequency caused by thermal expansion due to temperature changes in the beam based on incident light, thereby achieving the performance of "room temperature operation," "high sensitivity," and "high speed."

[0006] Furthermore, Non-Patent Document 2 describes an optical sensor configured with MEMS that detects infrared rays. The optical sensor described in Non-Patent Document 2 has a MEMS structure configured with paddles held by thin leads, and is configured to detect the torsional mode of the MEMS structure based on a change in resonance frequency caused by the thermal effect of light irradiated from outside.

[0007] Furthermore, Non-Patent Document 3 describes an optical sensor configured with SOI (silicon on insulator) MEMS that detects terahertz rays. The optical sensor in Non-Patent Document 3 employs an SOI cantilever structure, and is configured to drive the vibration of the cantilever structure due to the thermal effect of externally irradiated light, and detect the vibration amplitude of the cantilever.

[0008] Japanese Patent Application Publication No. 2018-146294

[0009] Y. Zhang, S. Hosono, N. Nagai, SH Song, and K. Hirakawa, “Fast and sensitive bolometric terahertz detection at room temperature through thermomechanical transduction”, Journal of Applied Physics 125, 151602 (2019); https: / / doi.org / 10.1063 / 1.5045256.XC Zhang, EB Myers, J. E. Sader, and ML Roukes, “Nanomechanical Torsional Resonators for Frequency-Shift Infrared Thermal Sensing” Nano Lett. 13, 1528 (2013); https: / / pubs.acs.org / doi / pdf / 10.1021 / nl304687pFroberger, K., et al. “SOI-based micro-mechanical terahertz detector operating at room-temperature." arXiv preprint arXiv:2204.03970 (2022).https: / / arxiv.org / pdf / 2204.03970.pdf

[0010] When applying an optical sensor to a spectroscopic system or the like, it is desirable that there be no dead zone in sensitivity to the frequency of incident light. The bolometer-type optical sensor described in Patent Document 1 and Non-Patent Document 1 is configured using a MEMS formed on a polar GaAs substrate. This optical sensor has a problem in that when input light in the terahertz or infrared region passes through the GaAs substrate, a dead zone occurs, causing a decrease in detection sensitivity in the terahertz to infrared region due to interaction with phonons in the GaAs crystal (see FIG. 14 ).

[0011] Furthermore, the response speed of a bolometer is determined by its thermal time constant. If the thermal conductivity is small, the thermal time constant increases, resulting in a slower response speed of the sensor. Generally, when a bolometer is formed in a small size, the thermal time constant of the element is reduced, enabling it to operate at a higher speed. However, GaAs material has a low thermal conductivity, and when it is formed to have a large light absorption area, the element size increases and the response speed deteriorates, which is a problem.

[0012] Furthermore, GaAs MEMS-based bolometers require the growth of a multilayer GaAs / AlGaAs heterostructure substrate (see Figure 15). The technology for growing GaAs / AlGaAs heterostructures is complex, difficult to control, and expensive, which makes large-scale manufacturing and application of MEMS bolometers difficult.

[0013] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical sensor, an optical detection device, and a terahertz / infrared Fourier spectrometer that can detect light in a wide wavelength band, including visible light, infrared light, and terahertz waves, with high sensitivity.

[0014] One aspect of the present invention is an optical sensor comprising: a vibration input section that generates vibrations based on an input signal; a vibration section formed by a MEMS structure using a silicon material, that vibrates based on the vibration transmitted by the vibration input section, and that has a doubly supported beam whose resonant frequency changes when light is input; and a vibration detection section that detects the vibration of the doubly supported beam.

[0015] According to the present invention, light in a wide wavelength band, including visible light, infrared light, and terahertz waves, can be detected with high sensitivity.

[0016] FIG. 1 is a diagram illustrating the configuration of a wideband photodetector according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating the configuration of an optical sensor. FIG. 3 is a diagram illustrating the transmission spectra of high-resistivity SOI and GaAs. FIG. 4 is a diagram illustrating measurement results of the resonance spectrum of an optical sensor. FIG. 5 is a diagram illustrating changes in the resonance spectrum when heat is input to an optical sensor. FIG. 6 is a diagram illustrating the function of the resonance frequency shift of an optical sensor corresponding to the input thermal power. FIG. 7 is a diagram illustrating changes in the resonance frequency when 530 nm visible light is input to an optical sensor. FIG. 8 is a diagram illustrating changes in the resonance frequency when 1.5 μm infrared light is input to an optical sensor. FIG. 9 is a diagram illustrating changes in the resonance frequency when 0.3 THz terahertz waves are input to an optical sensor. FIG. 10 is a diagram illustrating changes in the resonance frequency when light of 0 to 5 THz is input to an optical sensor. FIG. 11 is a diagram illustrating changes in the resonance frequency when light of 0 to 20 THz is input to an optical sensor. FIG. 12 is a diagram illustrating measurement results of the frequency shift when the modulation frequency is changed. FIG. 13 is a diagram illustrating the performance of an optical sensor and a conventional sensor. FIG. 14 is a diagram illustrating the performance of an optical sensor having a MEMS structure formed from conventional GaAs. FIG. 15 is a diagram illustrating the configuration of a substrate having a conventional multilayer GaAs / AlGaAs heterostructure. FIG. 1 is a diagram showing the configuration of a terahertz / infrared Fourier spectrometer to which an optical sensor is applied.

[0017] As shown in FIGS. 1 and 2 , the broadband photodetector 1 includes an optical sensor 10 that vibrates based on input light L input from a light source R, a vibration detection device 20 that detects the vibration of the optical sensor 10, and a phase synchronization unit 30 that detects and adjusts the frequency of the vibration of the optical sensor 10 based on the detection value of the vibration detection device 20. The light source R may be any light source. Examples of the input light L from the light source R include, but are not limited to, natural light, solid-state light emission such as laser light or LED light, transmitted light that has passed through a sample, reflected light from an object, and light emitted from a sample. The wavelength of the input light L is also not particularly limited as long as it is within the wavelength range detectable by the optical sensor 10, such as visible light, infrared light, or terahertz waves. The light source R does not have to be a component of the broadband photodetector 1.

[0018] The optical sensor 10 is formed in an optical element having, for example, a MEMS structure. In the following description, in the layer thickness direction of the optical sensor 10 (the Z-axis direction in the figure), the +Z direction will be referred to as the upper surface side, and the -Z direction will be referred to as the lower surface side. The above directions are defined for convenience and do not necessarily indicate the directions in the manner in which the optical sensor 10 is used.

[0019] The optical sensor 10 includes a substrate portion 13 formed in a plate shape, a vibration portion 11 formed on the substrate portion 13, and a sacrificial layer 12 for isolating the vibration portion 11 from the vibration portion 11. The optical sensor 10 is configured, for example, from a high-resistance SOI (Silicon on Insulator) wafer made of silicon (Si), a material used in semiconductor elements.

[0020] The sacrificial layer 12 is a silicon oxide film (SiO ２ ). The sacrificial layer 12 is formed into a pair of first and second legs 12A and 12B to support the vibration unit 11. The pair of first and second legs 12A and 12B are formed with a rectangular cross section in a plan view. A plate-shaped vibration unit 11 is provided on the upper surface 12C side of the sacrificial layer 12. The vibration unit 11 is formed of a silicon (Si) material. The vibration unit 11 has a both-supported beam 11A formed in a flat plate shape and extending so as to bridge the pair of sacrificial layers 12. A first support unit 11B supported by the first leg 12A is connected to one end of the both-supported beam 11A. A second support unit 11C supported by the second leg 12B is connected to the other end of the both-supported beam 11A. The both-supported beam 11A vibrates based on vibrations transmitted by a vibration input unit 16 described below.

[0021] The high-resistivity SOI used in the optical sensor 10 is, for example, p-type with a (100) crystal plane orientation and a resistivity exceeding 1000 ohm*cm, and has a stable transmission spectrum over a wide frequency band (see FIG. 3). Therefore, the optical sensor 10 formed from SOI can perform stable, highly sensitive optical measurements over a wide band. Compared to conventional optical sensors formed from GaAs, the optical sensor 10 formed from SOI has higher thermal conductivity and can realize a high-speed bolometer.

[0022] The doubly-supported beam 11A may be used as is as long as it can absorb the wavelength band of light to be measured. Furthermore, to achieve a consistent absorption rate across a wide wavelength band, it is preferable to provide a rectangular thin-film light-absorbing portion 15. This light-absorbing portion 15 can be made of a metal film, a high-absorption absorption film using a metasurface plasmon structure, or a doped film in which impurities are introduced into the surface of the doubly-supported beam 11A to match the sheet resistance with the vacuum electromagnetic wave resistance. When the light-absorbing portion 15 is made of a metal film, it can be formed by vapor deposition of nickel or a nickel-chromium (NiCr) alloy. The light-absorbing portion 15 heats up when light is input, and transmits the heat to the doubly-supported beam 11A. The impedance of the light-absorbing portion 15 matches the impedance of the input light or electromagnetic wave, converting the incident light into heat and transmitting it to the doubly-supported beam 11A. The light-absorbing portion 15 transmits its temperature to the doubly-supported beam 11A, causing it to expand and change the resonant frequency. The light absorption section 15 may be provided at any position as long as it can expand the both-supported beam 11A and change the resonant frequency, but it is preferable to provide it at the center of the both-supported beam 11A. A vibration input section 16 that inputs vibrations to the both-supported beam 11A is formed on the upper surface of the first support section 11B. A vibration detection section 17 that detects vibrations of the both-supported beam 11A is formed on the upper surface of the second support section 11C.

[0023] The vibration input unit 16 is formed, for example, by a pair of electrodes 16A and 16B. The pair of electrodes 16A and 16B are stacked in the thickness direction on the upper surface of the doubly-supported beam 11A and are provided at one longitudinal end of the doubly-supported beam 11A, i.e., on the side of the first support portion 11B in FIG. 2 . An insulating layer 16C made of a piezoelectric material is formed between the pair of electrodes 16A and 16B. The vibration input unit 16 is formed as a piezoelectric element that generates an electrostatic force between the pair of electrodes 16A and 16B based on a voltage input so as to generate a potential difference between the pair of electrodes 16A and 16B, thereby deforming the insulating layer 16C. The vibration input unit 16 generates vibrations based on an input signal output from a vibration generating unit 36 ​​(described below). The vibration input unit 16 vibrates when an input signal based on a voltage of a predetermined frequency generated by the vibration generating unit 36 ​​is input to the pair of electrodes 16A and 16B. The vibration input section 16 can transmit the generated vibration to the beam 11A, causing the beam 11A to vibrate.

[0024] The vibration input unit 16 may be configured as a piezoelectric element or an electrostatic element that applies a potential difference between the doubly supported beam 11A and the substrate unit 13 and inputs vibration to the doubly supported beam 11A based on the electrostatic effect. Alternatively, the vibration input unit 16 may be configured as an electromagnetic actuator that provides electrodes on the doubly supported beam 11A and inputs vibration to the doubly supported beam 11A based on the Lorentz force that is generated when a current flows through the electrodes in a magnetic field generated around the doubly supported beam 11A. The electromagnetic actuator may be configured to pass an AC current through the electrodes in a DC magnetic field, or may be configured to pass a DC current through the electrodes in an AC magnetic field.

[0025] The vibration detection unit 17 is formed, for example, by a pair of electrodes 17A and 17B. The vibration detection unit 17 has a configuration similar to that of the vibration input unit 16. The pair of electrodes 17A and 17B are stacked in the layer thickness direction on the upper surface of the doubly supported beam 11A and are provided at the other longitudinal end of the doubly supported beam 11A, i.e., on the support portion 11C side in FIG. 2 . An insulating layer 17C made of a piezoelectric material is formed between the pair of electrodes 17A and 17B. The vibration detection unit 17 is formed by a pair of electrodes 17A and 17B. The vibration detection unit 17 is formed as a piezoelectric element that generates a potential difference between the pair of electrodes 17A and 17B when the insulating layer 17C deforms. The vibration detection unit 17 deforms in response to vibrations of a predetermined frequency generated in the doubly supported beam 11A, and outputs an output signal based on a voltage of a predetermined frequency in response to the deformation of the insulating layer 17C.

[0026] The vibration detection unit 17 may be formed of a piezo-resistive element that detects a resistance that changes in response to a stress generated by the vibration of the doubly supported beam 11 A, other than a piezoelectric element. The vibration detection unit 17 may be a laser Doppler vibrometer that receives reflected light of a laser beam irradiated on the doubly supported beam 11 A and detects the vibration of the doubly supported beam 11 A based on the Doppler effect.

[0027] The vibration detection device 20 amplifies the signal output from the vibration detection unit 17 and outputs the detection signal to the phase synchronization unit 30. The phase synchronization unit 30 is configured as a general phase synchronization circuit. The phase synchronization unit 30 includes, for example, a phase comparator 32 that receives the output value of the detection signal output from the vibration detection device 20, a low-pass filter 34 connected downstream of the phase comparator 32, and a vibration generation unit 36 ​​that is connected downstream of the low-pass filter 34 and is also connected to the phase comparator 32 and the vibration input unit 16.

[0028] The phase comparator 32 compares the phase of the detection signal output from the vibration detection device 20 with a reference signal and outputs a signal indicating the phase difference. The low-pass filter 34 receives the signal output from the phase comparator 32 and outputs an output signal by blocking high frequencies from the signal. The vibration generating unit 36 ​​outputs a signal whose frequency is changed in a direction that cancels out the signal from the low-pass filter 34. The signal output from the vibration generating unit 36 ​​is input as an input signal to the vibration input unit 16 of the optical sensor 10 and is also input as a reference signal to the phase comparator 32. The signal output from the vibration generating unit 36 ​​is input to the vibration input unit 16 as an input signal having the resonant frequency of the doubly-supported beam 11A of the optical sensor 10. The vibration input unit 16 generates vibrations based on the input signal, causing the doubly-supported beam 11A to vibrate.

[0029] Next, the operation of the broadband photodetector 1 will be described. When no light is input to the optical sensor 10, the doubly supported beam 11A vibrates at a natural resonance frequency f ０ The initial value of the angular frequency ω corresponding to ０ = f ０ / 2π is expressed by the following equation (1).

[0030]

[0031] where Young's modulus of the doubly supported beam 11A is E, density is ρ, and constant according to the mode is μ n , the span length of the both-supported beam 11A: L, and the thickness of the both-supported beam 11A: t. When light is irradiated from the light source R onto the optical sensor 10, the light irradiated onto the both-supported beam 11A is converted into heat in the light absorbing section 15. The heat generated in the light absorbing section 15 is transferred to the both-supported beam 11A. When the temperature of the both-supported beam 11A rises, the both-supported beam 11A thermally expands. Since one end of the both-supported beam 11A is restrained by the first support section 11B and the other end is restrained by the second support section 11C, the both-supported beam 11A is compressed in the longitudinal direction in response to the thermal expansion, and stress σ is generated inside. The resonant frequency f of the both-supported beam 11A when stress σ is applied is ０ The angular frequency ω0(σ) = f ０ / 2π is expressed by the following equation (2).

[0032]

[0033] As shown in equation (2), the resonant frequency f ０ The angular frequency ω(σ) corresponding to the change in the resonant frequency of the doubly-supported beam 11A changes linearly with an increase in the thermal stress σ (<0). Here, by detecting the resonant frequency of the doubly-supported beam 11A using the optical sensor 10, the power of the input light can be calculated. When the resonant frequency of the doubly-supported beam 11A to which light is input changes, the phase synchronization unit 30 adjusts the vibration generating unit 36 ​​so that a signal of the changed resonant frequency is output. The resonant frequency of the doubly-supported beam 11A can be obtained by observing the signal output from the vibration generating unit 36. Therefore, the wideband photodetector 1 can detect the input of light by shifting the resonant frequency of the doubly-supported beam 11A based on the light input to the optical sensor 10.

[0034] Based on the optical sensor 10, the resonant frequency f ０ In order to detect minute changes in k, it is desirable that the quality factor (Q value) representing the state of vibration of the mechanical resonance of the doubly supported beam 11A is as high as possible. Ｂ is the Boltzmann constant, T is the temperature, f ０ is the resonant frequency, k is the spring constant of the doubly supported beam 11A, Q is the Q value, and A is the amplitude, then the frequency noise density n ｆ The relationship between the Q value and the Q factor is expressed by the following equation (3).

[0035]

[0036] 4 shows the measurement results of the resonance spectrum of the optical sensor 10 measured based on the wideband photodetector 1. According to the measurement results, the Q value of the optical sensor 10 was approximately 17,000. The optical sensor 10 exhibits a value more than twice as high as that of a conventional MEMS optical sensor formed from GaAs. Therefore, the optical sensor 10 is capable of measuring the frequency of light with lower noise and greater precision than a conventional MEMS optical sensor formed from GaAs.

[0037] FIG. 5 shows the change in the resonance spectrum when heat is input to the optical sensor 10. As shown, the optical sensor 10 generates thermal stress and softens due to the input of light, resulting in a decrease in the resonance frequency. FIG. 6 shows the function of the resonance frequency shift of the optical sensor 10 corresponding to the input thermal power. In the figure, (A) shows the measurement results using a doubly supported beam 11A formed with dimensions of 100 μm × 30 μm × 2.5 μm. As can be seen in FIG. 5, the frequency shift increases linearly with increasing thermal power, and therefore the normalized thermal response of this sample is expressed by the following equation (4):

[0038]

[0039] Such thermal response can be adjusted by thinning the thickness of the doubly supported beam 11A or lengthening the span length. In Figure 6, (B) shows the measurement results when a doubly supported beam 11A with a thickness of 0.8 μm is used. As shown in the figure, (B) shows a frequency shift compared to (A), and the thermal response R is about 26.5 W. －１ This measurement result was close to the thermal response of an optical sensor made of GaAs.

[0040] FIG. 7 shows the change in resonant frequency when 530 nm visible light is input to the optical sensor 10. FIG. 8 shows the change in resonant frequency when 1.5 μm infrared light is input to the optical sensor 10. FIG. 9 shows the change in resonant frequency when 0.3 THz terahertz waves are input to the optical sensor 10 using a terahertz wave multiplier. FIG. 10 shows the change in resonant frequency when light from a thermal light source (light bulb) is input to the optical sensor 10 via a far-infrared pass filter (cutoff frequency: 5 THz) (i.e., the input light is light from 0 to 5 THz). FIG. 11 shows the change in resonant frequency when light from a thermal light source (light bulb) is input to the optical sensor 10 via a far-infrared pass filter (cutoff frequency: 20 THz) (i.e., the input light is light from 0 to 20 THz). As shown in the figures, the optical sensor 10 can detect a resonant frequency that changes based on the input light. It can be seen that the optical sensor 10 has sensitivity to light in the frequency bands of visible light and infrared light.

[0041] The optical sensor 10 can detect light in a predetermined frequency band at high speed. The photothermal response speed of the optical sensor 10 is determined based on its thermal time constant. If the specific heat of silicon is c and the thermal conductivity is κ, the thermal time constant of the optical sensor 10 is expressed by the following equation (5):

[0042]

[0043] The response speed of the optical sensor 10 is 1 / τ, so the smaller τ is, the faster the response of the optical sensor 10. To demonstrate the high-speed response speed of the optical sensor 10, the modulation frequency of the input light was modulated and the shift in the resonant frequency was measured.

[0044] 12 shows the measurement results of the frequency shift Δf when the modulation frequency is changed. As shown in the figure, when optical sensor 10 is compared with a conventional optical sensor of the same size formed from GaAs, the thermal time constant of optical sensor 10 is approximately 35 μs, while the thermal time constant of the conventional optical sensor formed from GaAs is approximately 100 μs. As shown in this measurement result, when optical sensor 10 and an optical sensor of the same shape formed from GaAs are compared, it is found that the thermal response of optical sensor 10 is approximately three times faster than the thermal response of the conventional optical sensor formed from GaAs.

[0045] 13, the optical sensor 10 has a detection speed (Hz) that is 100 to 1000 times faster than conventional thermal sensors that utilize changes in resistance or capacitance, while maintaining the same sensitivity. The broadband photodetector 1 has an optical sensor 10 with a MEMS structure formed from an SOI material, making it possible to realize a bolometer with high resistance and high optical transmittance at low cost. The broadband photodetector 1 can realize a high-performance bolometer that operates at room temperature based on the optical sensor 10 and has a wide bandwidth, high sensitivity, high speed, and low cost.

[0046] The optical sensor 10 is formed using an SOI substrate, which provides high transmittance over a wide frequency range and is capable of measuring wavelengths ranging from visible light to infrared and terahertz waves, making it possible to realize a high-speed, highly sensitive sensor that operates at room temperature. The optical sensor 10 uses an SOI substrate structure, which is less expensive than GaAs heterostructures, which require a complex growth process, making it possible to mass-produce MEMS bolometers at low cost. The optical sensor 10 uses common silicon semiconductor technology, making it easy to mass-produce.

[0047] The optical sensor 10 has high sensitivity to light in a wide wavelength band, from visible light to infrared and terahertz waves, and therefore has a detection speed approximately three times faster than a conventional MEMS optical sensor formed in the same shape from GaAs. Because the optical sensor 10 is formed from a silicon-based material, the growth process is simplified and it can be formed inexpensively. The broadband photodetector 1 incorporating the optical sensor 10 has no insensitive band that reduces detection sensitivity in the terahertz to infrared region, and can realize a broadband, high-speed, and highly sensitive photodetector, spectrometer, or biological imaging device.

[0048] However, attempts to fabricate a doubly-supported beam resonator optical sensor using silicon-based materials have been plagued by the problem of high internal stress in the beam structure deposited by physical deposition. However, the present inventors discovered that this internal stress problem can be resolved by employing a MEMS structure formed from a crystalline SOI material (e.g., a single-crystal SOI substrate) with low internal stress. Thus, the performance of an optical sensor can be further improved by utilizing a MEMS doubly-supported beam structure formed from SOI material. For example, the example described in Non-Patent Document 2 uses a physically-deposited a-Si film, which results in relatively high internal stress in the MEMS structure. As a result, only the torsion mode, which has insufficient temperature sensitivity, can be used. Compared to the example described in Non-Patent Document 2, the temperature sensitivity of the above-described optical sensor 10 is approximately 20 times higher. While Non-Patent Document 3 describes an example using an SOI substrate, this does not take into account the internal stress of the beam structure described above. The example described in Non-Patent Document 3 employs a cantilever structure, so the initial stress within the structure is irrelevant. Furthermore, Non-Patent Document 3 does not discuss the crystallinity of the material. Furthermore, in the example described in Non-Patent Document 3, a cantilever structure is used, so the temperature sensitivity is approximately 10 nW / Hz ０．５ , and the optical sensor 10 is more than ten times better.

[0049] The broadband photodetector 1 incorporating the optical sensor 10 can be applied to industrial fields that utilize near-infrared, infrared, and terahertz frequency bands. The broadband photodetector 1 incorporating the optical sensor 10 can realize a terahertz / infrared Fourier transform spectrometer (FTIR), which is an essential device in fields such as materials, chemistry, pharmaceuticals, and biotechnology. Below, an FTIR incorporating the optical sensor 10 will be described. In the following description, the same components as those in the above embodiment will be designated by the same names and reference numerals, and duplicate descriptions will be omitted where appropriate.

[0050] As shown in FIG. 16 , the FTIR 100 includes a broadband light detecting device 1 equipped with an optical sensor 10, a lens unit N, a light source R, an interference light generating unit U that generates interference light, and a computing device 40 that analyzes the light detected by the broadband light detecting device 1. The FTIR 100 is configured as a spectroscopic device that measures the interference waveform of light using an interferometer and measures the spectral intensity distribution of the light by Fourier transforming the measured value. When the FTIR 100 is in use, a sample S is placed in the broadband light detecting device 1, and the FTIR 100 can investigate the optical properties of the sample S. Note that, in FIG. 16 , the sample S is placed between the semitransparent mirror U1 of the interference light generating unit U and the lens unit N, but this placement is not limited thereto and may be placed at any position where spectroscopic measurement is possible. The lens unit N is formed in a lens shape from silicon and focuses the input light and inputs it to the optical sensor 10. The computing device 40 analyzes and outputs the spectrum of the light input to the optical sensor 10. The arithmetic unit 40 is, for example, an information processing terminal device configured by a personal computer or the like.

[0051] The interference light generating unit U is, for example, a Michelson interferometer, and includes a half mirror U1, a first reflecting mirror U2 formed on a fixed mirror, and a second reflecting mirror U3 formed on a movable mirror. The half mirror U1 receives light L1 input from the light source R at an oblique angle and splits the light into two beams: a first reflected light L2 and a second transmitted light L3. The first light L2 is reflected by the first reflecting mirror U2 and returns to the half mirror U1. The second light L3 is reflected by the second reflecting mirror U3 and returns to the half mirror U1.

[0052] The first light L2 and the second light L3 are combined in the semitransparent mirror U1. The second reflecting mirror U3 is movable in the optical path direction, and an optical path difference occurs between the optical path length of the second light L3 and the optical path length of the first light L2. As a result, a phase difference occurs between the first light L2 and the second light L3 in the semitransparent mirror U1, and interference light L4 is generated in the semitransparent mirror U1. The interference light L4 generated in the semitransparent mirror U1 is focused by a lens unit N formed by a silicon lens and input to the optical sensor 10. The interference light L4 input to the optical sensor 10 vibrates the double-supported beam 11A, and the vibration is detected by the vibration detection device 20. The resonant frequency of the double-supported beam 11A changes based on the interference light L4. The phase synchronization unit 30 detects the vibration frequency of the optical sensor 10. The detection value detected by the phase synchronization unit 30 is input to the calculation device 40. The arithmetic unit 40 analyzes the spectrum of the light L1 based on the detection value detected by the phase synchronization unit 30. The arithmetic unit 40 performs Fourier analysis on the interference waveform of the interference light L4 at the detection value, and performs spectrum analysis of the light L1 output from the light source R. The arithmetic unit 40 outputs the spectrum of the light L1 for each wavelength component.

[0053] Because the modulation frequency of light caused by the movement of the second reflecting mirror U3 is proportional to the frequency of the light and the movement speed of the second reflecting mirror U3, the scanning speed of the FTIR 100 depends on the detection speed of the optical sensor. The light intensity modulation frequency of the FTIR 100 is calculated by fm = 2 * f / c * v, where f is the frequency of the light, c is the speed of the light, and v is the speed of the moving mirror. For example, if the light is 10 μm infrared (frequency 30 THz) and the movement speed of the moving mirror is 10 mm / s, the modulation frequency of the light is 2 kHz.

[0054] The FTIR 100 incorporating the optical sensor 10 has a detection speed approximately 100-1000 times faster than the pyroelectric detectors used in conventional FTIR, enabling high-speed, high-sensitivity measurement of the spectral distribution of light. The FTIR 100 can realize a multi-channel spectrometer that analyzes the spectral distribution of light in the near-infrared, infrared, and terahertz frequency bands with high speed and high sensitivity. Furthermore, the interference light generation unit U may be replaced with a Michelson interferometer or any other interferometer that generates interference light. Furthermore, the optical sensor 10 in the FTIR 100 may be an array of elements, and by integrating the circuitry of the vibration detection unit, it is possible to realize an imaging element or thermography that can detect near-infrared, infrared, and terahertz waves at high speed, which can be applied to night driving assistance devices, etc.

[0055] The above-described arithmetic device 40 is realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device such as an HDD (Hard Disk Drive) or flash memory provided in the arithmetic device 40, or may be stored in a removable storage medium such as a DVD or CD-ROM and installed by inserting the storage medium into a drive device.

[0056] Although the present invention has been described above using the embodiments, the present invention is not limited to these embodiments, and various modifications and substitutions can be made without departing from the spirit of the present invention. The configurations described in the above embodiments may be substituted for each other.

[0057] REFERENCE SIGNS LIST 10 Optical sensor 11 Vibration section 11A Double-supported beam 15 Light absorption section 16 Vibration input section 17 Vibration detection section 20 Vibration detection device 30 Phase synchronization section 36 Vibration generation section 40 Calculation device L Input light L1 Light R Light source

Claims

1. a vibration input unit that generates vibrations based on an input signal; a vibration section having a doubly supported beam formed by a MEMS structure using a silicon material, vibrating based on the vibration transmitted by the vibration input section and having a resonant frequency that changes when light is input; a vibration detection unit that detects vibration of the double-supported beam, The MEMS structure is formed of a high-resistance SOI (Silicon on Insulator) substrate (excluding the phononic crystal); Light sensor.

2. The MEMS structure is formed of an SOI substrate having a flat surface. The optical sensor of claim 1 .

3. The double-supported beam is provided between the vibration input unit and the vibration detection unit, and has a light absorption unit to which temperature is transmitted by inputting light.

3. The optical sensor according to claim 1 or 2.

4. The vibration input portion is formed by a piezoelectric element provided on one end side of the double-supported beam in the longitudinal direction. The optical sensor according to claim 3 .

5. The vibration input portion is formed by an electrostatic element provided on one end side of the double-supported beam in the longitudinal direction. The optical sensor according to claim 3 .

6. The vibration detection unit is formed of a piezoelectric element provided on the other end side of the double-supported beam in the longitudinal direction. The optical sensor according to claim 3 .

7. The vibration detection unit is formed of a piezoresistance element provided on the other end side of the double-supported beam in the longitudinal direction. The optical sensor according to claim 3 .

8. The MEMS structure includes: A substrate portion formed in a flat plate shape; A pair of sacrificial layers formed on the substrate portion; The vibration unit is made of a silicon material and has the two-sided beam formed in a flat plate shape so as to bridge the pair of sacrificial layers. The optical sensor according to claim 3 .

9. an optical sensor including a vibration input unit that generates vibrations based on an input signal, a vibration unit formed of a MEMS structure using a silicon material, that vibrates based on the vibration transmitted by the vibration input unit, and that has a double-supported beam whose resonance frequency changes when light is input, and a vibration detection unit that detects the vibration of the double-supported beam; a vibration detection device that amplifies and outputs the vibration of the optical sensor; a phase synchronization unit that detects a frequency of vibration of the optical sensor based on an output value of the vibration detection device, The MEMS structure is formed of a high-resistance SOI substrate (excluding phononic crystals); Light detection device.

10. The MEMS structure is formed of an SOI substrate having a flat surface.

10. The optical detection device according to claim 9.

11. an optical sensor including a vibration input unit that generates vibrations based on an input signal, a vibration unit formed of a MEMS structure using a silicon material, that vibrates based on the vibration transmitted by the vibration input unit, and that has a double-supported beam whose resonance frequency changes when light is input, a light absorption unit that transmits temperature to the double-supported beam when light is input, and a vibration detection unit that detects the vibration of the double-supported beam; A light source that inputs input light to the optical sensor; a vibration detection device that amplifies and outputs the vibration of the optical sensor; a phase synchronization unit that detects a frequency of vibration of the optical sensor based on an output value of the vibration detection device; a calculation unit that analyzes the spectrum of the light based on the detection value detected by the phase synchronization unit, The MEMS structure is formed of a high-resistance SOI substrate (excluding phononic crystals); Terahertz and infrared Fourier spectrometer.

12. The MEMS structure is formed of an SOI substrate having a flat surface. The terahertz / infrared Fourier spectrometer according to claim 11.

13. The resistivity of the SOI substrate is greater than 1000 Ω cm; The optical sensor of claim 1 .