JP2017084991A - Terahertz wave generator, imaging device, camera, and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact terahertz wave generator capable of exiting stabilized terahertz waves, and to provide a camera, an imaging device, and a measurement device.SOLUTION: A terahertz wave generator 1 has an optical pulse generation unit 40 including a quantum well layer 32, and generating optical pulses, and a photoconduction antenna 50 including the quantum well layer 32. The optical pulse generation unit 40 includes a forward bias application unit 42 to be applied with a forward bias voltage, a reverse bias application unit 44 to be applied with a reverse bias voltage, and a distribution Bragg reflection unit 46 for reflecting a part of the light guiding the quantum well layer 32. The photoconduction antenna 50 receives the light transmitted through the distribution Bragg reflection unit 46, and generates terahertz waves.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a terahertz wave generation device, an imaging device, a camera, and a measurement device.

In recent years, a terahertz wave, which is an electromagnetic wave having a frequency of 100 GHz or more and 30 THz or less, has attracted attention. The terahertz wave can be used for, for example, each measurement such as imaging and spectroscopic measurement, non-destructive inspection, and the like.
This terahertz wave generating device that generates a terahertz wave is irradiated with a light source device that generates a light pulse (pulse light) having a pulse width of about sub-p seconds (several hundreds of seconds), and a light pulse generated by the light source device. And a photoconductive antenna that generates terahertz waves.
As the photoconductive antenna, for example, in Patent Document 1, an optical waveguide, a microstrip line, and a photoconductive element in which a plurality of semiconductor layers for converting light into terahertz waves are stacked are integrated on the same substrate. Are disclosed.

JP 2006-66864 A

  However, since the light source device and the photoconductive antenna are not integrated in the terahertz wave generation device having the photoconductive antenna described in Patent Document 1, the optical waveguides of the light source device and the photoconductive antenna are aligned with high accuracy. However, the light pulse emitted from the light source device is not incident on the photoconductive antenna but leaks to the outside, and there is a possibility that the terahertz wave cannot be generated efficiently.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A terahertz wave generator according to this application example includes a quantum well layer, and includes an optical pulse generation unit that generates an optical pulse, and a photoconductive antenna including the quantum well layer, The optical pulse generator includes a forward bias applying unit to which a forward bias voltage is applied, a reverse bias applying unit to which a reverse bias voltage is applied, and a distributed Bragg that reflects a part of the light guided through the quantum well layer. The photoconductive antenna generates a terahertz wave upon receiving a light pulse transmitted through the distributed Bragg reflector.

  According to this application example, the quantum well layer that guides the optical pulse generated by the optical pulse generation unit is formed integrally with the optical pulse generation unit and the photoconductive antenna that generates the terahertz wave. Alignment between the optical waveguides of the optical pulse generator and the photoconductive antenna is unnecessary, and a terahertz wave can be generated efficiently. In addition, since the reverse bias applying unit is provided in the optical pulse generation unit, the generated optical pulse can be compressed to reduce the pulse width, and an optical pulse having high intensity can be generated. Furthermore, since the distributed Bragg reflector is provided on the photoconductive antenna side, only a light pulse having a desired wavelength can be incident on the photoconductive antenna, and a terahertz wave having a desired wavelength can be efficiently generated. it can.

  Application Example 2 In the terahertz wave generator according to the application example described above, the distributed Bragg reflector includes a first cladding layer, the quantum well layer, and a second cladding layer, and the second cladding layer. Preferably has a plurality of convex portions toward the quantum well layer.

  According to this application example, since the second cladding layer has a plurality of convex portions toward the quantum well layer side, Bragg reflection that reflects only light pulses of a specific wavelength can be configured. Only a light pulse having a desired wavelength can be guided to the photoconductive antenna to generate a terahertz wave having the desired wavelength.

  Application Example 3 In the terahertz wave generation device according to the application example, the distributed Bragg reflector includes a first cladding layer, the quantum well layer, and a second cladding layer, and the second cladding It is preferable that the layer has a plurality of grooves that are open on the side opposite to the quantum well layer side.

  According to this application example, the second clad layer has a plurality of grooves that are opened on the side opposite to the quantum well layer side, thereby configuring a Bragg reflection that reflects only a light pulse of a specific wavelength. Therefore, only a light pulse having a desired wavelength can be guided to the photoconductive antenna, and a terahertz wave having a desired wavelength can be generated.

  Application Example 4 In the terahertz wave generation device according to the application example, it is preferable that a reverse bias voltage is applied to the photoconductive antenna.

  According to this application example, the acceleration of the optical carrier is increased by applying a reverse bias voltage to the photoconductive antenna. Therefore, the intensity of the terahertz wave emitted from the photoconductive antenna can be increased.

  Application Example 5 An imaging apparatus according to this application example includes the terahertz wave generation apparatus according to the application example described above, and terahertz wave detection that detects a terahertz wave that has been emitted from the terahertz wave generation apparatus and transmitted or reflected from an object. And an image forming unit that generates an image of the object based on the detection result of the terahertz wave detection unit.

  According to this application example, since the small terahertz wave generator in which the optical pulse generation unit and the photoconductive antenna are integrated is provided, a small and high-performance imaging apparatus can be configured.

  Application Example 6 A camera according to this application example includes the terahertz wave generation device according to the application example described above, a terahertz wave detection unit that detects a terahertz wave that is emitted from the terahertz wave generation device and reflected by an object. And a storage unit for storing the detection result of the terahertz wave detection unit.

  According to this application example, since a small terahertz wave generation device in which the optical pulse generation unit and the photoconductive antenna are integrated is provided, a small and high-performance camera can be configured.

  Application Example 7 A measurement apparatus according to this application example includes the terahertz wave generation device according to the application example described above, and terahertz wave detection that detects a terahertz wave that has been emitted from the terahertz wave generation device and transmitted or reflected from an object. And a measurement unit that measures an object based on a detection result of the terahertz wave detection unit.

  According to this application example, since a small terahertz wave generation device in which the optical pulse generation unit and the photoconductive antenna are integrated is provided, a small and high-performance measurement device can be configured.

  Application Example 8 In the measurement apparatus according to the application example, the terahertz wave detection unit is irradiated with a light pulse emitted from the terahertz wave generation device, and the terahertz wave generation device to the terahertz wave detection unit. It is preferable to provide a delay optical system that changes the optical path length of the light pulse.

  According to this application example, since the terahertz wave generation device can emit the terahertz wave and the optical pulse at the same time, the emitted optical pulse can be delayed from the terahertz wave by the delay optical system and irradiated onto the object or the like. it can. Therefore, a small and high-performance measuring device can be configured.

1 is a perspective view showing a configuration of a terahertz wave generation device according to a first embodiment of the present invention. The schematic sectional drawing of the AA in FIG. The schematic sectional drawing of the AA in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing of the AA in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing of the AA in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing of the BB line in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing of the BB line in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing of the BB line in FIG. 1 explaining the manufacturing process of a terahertz wave generator. The schematic sectional drawing which shows the structure of the terahertz wave generator which concerns on 2nd Embodiment of this invention. 1 is a block diagram showing a configuration of an imaging apparatus according to an embodiment of the present invention. The top view which shows the terahertz wave detection part of the imaging device shown in FIG. The graph which shows the spectrum in the terahertz band of a target object. The figure of the image which shows distribution of the substances A, B, and C of a target object. 1 is a block diagram showing a configuration of a camera according to an embodiment of the present invention. 1 is a perspective view illustrating a configuration of a camera according to an embodiment of the present invention. The block diagram which shows the structure of the measuring device which concerns on embodiment of this invention. The block diagram which shows the structure of the terahertz spectroscopy analyzer as a measuring device which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is different from the actual scale so that each layer and each member can be recognized.

[Terahertz wave generator]
<First Embodiment>
First, a terahertz wave generator 1 according to a first embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a perspective view showing a configuration of a terahertz wave generating apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic sectional view taken along line AA in FIG.

  As shown in FIG. 1, the terahertz wave generator 1 includes a substrate 10 that is a semiconductor substrate, a buffer layer 12 provided on the substrate 10, a first cladding layer 14 provided on the buffer layer 12, An active layer 16 provided on the first cladding layer 14, a second cladding layer 18 provided on the active layer 16, an insulating layer 20 and a contact layer 22 provided on the second cladding layer 18, and an insulating layer; 20 and a plurality of second electrodes 26a, 26b, 26c provided on the contact layer 22 and a first electrode 24 provided on the opposite side of the substrate 10 from the side on which the buffer layer 12 is provided. doing.

As the substrate 10, an n-type semiconductor such as an n-type GaAs substrate can be used.
The buffer layer 12 can improve the crystallinity of the layer formed above. For example, an n-type GaAs layer having better crystallinity than the substrate 10 can be used.

The first cladding layer 14 can be an n-type semiconductor, such as an n-type Al _0.5 Ga _0.5 As layer.
The active layer 16 may be a layer in which i-type semiconductors are stacked, for example, a layer in which i-type GaAs layers and i-type Al _0.3 Ga _0.7 As layers are alternately stacked.
For the second cladding layer 18, a p-type semiconductor such as a p-type Al _0.5 Ga _0.5 As layer can be used.

The insulating layer 20 is not particularly limited as long as it is an insulating material, and examples thereof include fluorine-based resins, polyimides, porazine-based compounds, hydrogenated hexane, benzocyclobutene, SiN, and SiO ₂ .
The contact layer 22 can be a p-type semiconductor such as a p-type GaAs layer.

As the first electrode 24, a layer in which a Cr layer, an AuGe layer, a Ni layer, and an Au layer are stacked in this order from the substrate 10 side can be used.
As the second electrodes 26a, 26b, and 26c, a layer in which a Cr layer, a Pt layer, a Ti layer, a Pt layer, and an Au layer are stacked in this order from the contact layer 22 side can be used.

  Further, in the terahertz wave generator 1, the active layer 16 guides a guide layer 30 provided on the first cladding layer 14 and an optical pulse provided on the guide layer 30 as shown in FIG. 2. A quantum well layer 32; a barrier layer 34 provided on the quantum well layer 32; a quantum well layer 32 provided on the barrier layer 34; and a guide layer 30 provided on the quantum well layer 32. It is configured. In the present embodiment, the structure is called a multiple quantum well in which a plurality of quantum well layers 32 and barrier layers 34 are alternately provided between the guide layers 30. However, the present invention is not limited to this, and a single quantum well structure or a single quantum well layer 32 in which the upper and lower sides of the quantum well layer 32 are sandwiched between the guide layers 30 may be used.

  The constituent material of the guide layer 30 and the barrier layer 34 is an i-type semiconductor, for example, an i-type AlGaAs layer. The constituent material of the quantum well layer 32 is an i-type semiconductor, for example, an i-type GaAs layer.

Furthermore, the terahertz wave generation device 1 includes an optical pulse generation unit 40 that generates an optical pulse, and a photoconductive antenna 50 that receives the optical pulse generated by the optical pulse generation unit 40 and generates a terahertz wave. Yes. Further, in the terahertz wave generating device 1, the optical pulse generation unit 40 and the photoconductive antenna 50 are integrated, that is, integrated on the same substrate 10, and the active layer 16 including the quantum well layer 32 in which the optical pulse is guided. Are integrated with the optical pulse generator 40 and the photoconductive antenna 50.
The terahertz wave means an electromagnetic wave having a frequency of 100 GHz to 30 THz, particularly an electromagnetic wave of 300 GHz to 3 THz.

  Next, the optical pulse generation unit 40 and the photoconductive antenna 50 constituting the terahertz wave generation device 1 will be described.

  The optical pulse generator 40 includes a forward bias applying unit 42 having a second electrode 26a provided on the contact layer 22, a reverse bias applying unit 44 having a second electrode 26b provided on the contact layer 22, and a distribution. And a Bragg reflector 46. The forward bias applying unit 42 is applied with a forward voltage between the first electrode 24 and the second electrode 26a from the power source 52a. The reverse bias applying unit 44 applies a reverse voltage from the power source 52b between the first electrode 24 and the second electrode 26b.

  The forward bias applying unit 42 has a pin structure including the second cladding layer 18 that is a p-type semiconductor, the active layer 16 that is an i-type semiconductor, and the first cladding layer 14 that is an n-type semiconductor. Therefore, each of the first cladding layer 14 and the second cladding layer 18 is a layer having a larger forbidden band width and a smaller refractive index than the active layer 16, and thus the active layer 16 has a function of amplifying light. The first cladding layer 14 and the second cladding layer 18 have a function of confining injected carriers (electrons and holes) and light with the active layer 16 interposed therebetween.

  Therefore, when a forward voltage is applied between the first electrode 24 and the second electrode 26a (pin structure part), electrons and holes are recombined in the active layer 16, and light is emitted by this recombination. . Luminescence occurs in a chain-induced manner. The emitted light has a boundary surface between the reverse bias application unit 44 and the distributed Bragg reflection unit 46 and a first side surface 28a that is an end of the forward bias application unit 42 opposite to the reverse bias application unit 44 side. The light intensity is amplified by reciprocating between them.

  The reverse bias applying unit 44 also has a pin structure including the second cladding layer 18 that is a p-type semiconductor, the active layer 16 that is an i-type semiconductor, and the first cladding layer 14 that is an n-type semiconductor. However, when a reverse voltage is applied between the first electrode 24 and the second electrode 26b (pin structure portion), the saturable absorber has a characteristic that the absorptance is lower as the amount of incident light is larger.

  For this reason, the light generated by the forward bias applying unit 42 has a higher absorption rate at the skirt portion of the light waveform than at the peak portion, so that the more light that passes through the reverse bias applying unit 44 that is a saturable absorber, The bottom part of the waveform is cut to form an optical pulse with a narrow pulse width. Further, since the saturable absorber also functions to align the phase of the emitted light, it passes through the reverse bias applying unit 44 many times, and the optical pulse is compressed by compressing the optical pulse and reducing the pulse width. Can be generated.

  Since the forward bias applying unit 42 emits light in a plurality of longitudinal modes, the forward bias applying unit 42 and the reverse bias applying unit 44 can generate optical pulses having a plurality of wavelengths and a narrow pulse width. The light pulses generated by the forward bias applying unit 42 and the reverse bias applying unit 44 are transmitted from the first side surface 28a of the quantum well layer 32 on the forward bias applying unit 42 side to the outside, and with the reverse bias applying unit 44 and distributed Bragg reflection. The light is emitted from the boundary surface with the portion 46 to the distributed Bragg reflector 46.

  The distributed Bragg reflector 46 includes the first cladding layer 14, the quantum well layer 32 constituting the active layer 16, and the second cladding layer 18. The second cladding layer 18 has a plurality of convex portions 48 toward the quantum well layer 32 side. Since the convex portions 48 of the second cladding layer 18 are periodically arranged, it can act as a diffraction grating and can selectively reflect light of a specific wavelength. Therefore, it is possible to transmit only an optical pulse having a desired wavelength from among the optical pulses having a plurality of wavelengths generated by the forward bias applying unit 42 and the reverse bias applying unit 44 and to enter the photoconductive antenna 50.

If the width dimension L1 of the guide layer 30 of the active layer 16 and the width dimension L2 of the convex portion 48 of the second cladding layer 18 are the same as the refractive index n of the guide layer 30 and the second cladding layer 18, ( m × are arranged such that λ _0/4 × n). Here, the diffraction order m is a natural number, usually 1, and when the desired wavelength λ ₀ is 800 nm and the refractive index n is 3.5, L1 and L2 are 57 nm.

The photoconductive antenna 50 has a second electrode 26c provided on the contact layer 22, and a reverse voltage is applied between the first electrode 24 and the second electrode 26c from the power source 52c.
By applying a reverse bias voltage to the photoconductive antenna 50, the acceleration of the optical carrier of a light pulse having a desired wavelength that has passed through the distributed Bragg reflector 46 and entered the photoconductive antenna 50 is increased. The strength can be increased.
Further, the terahertz wave generated by the photoconductive antenna 50 is emitted from the second side surface 28b of the quantum well layer 32 on the side opposite to the distributed Bragg reflector 46 side of the photoconductive antenna 50.

  As described above, in the terahertz wave generation device 1 according to this embodiment, the quantum well layer 32 that guides the optical pulse generated by the optical pulse generation unit 40 generates the terahertz wave with the optical pulse generation unit 40. Since it is formed integrally with the photoconductive antenna 50, alignment between the optical waveguides of the optical pulse generator 40 and the photoconductive antenna 50 is not necessary, and a terahertz wave can be generated efficiently. Further, since the reverse bias applying unit 44 is provided in the optical pulse generation unit 40, the generated optical pulse can be compressed to reduce the pulse width, and an optical pulse having high intensity can be generated. Further, since the distributed Bragg reflector 46 is provided between the reverse bias applying unit 44 and the photoconductive antenna 50, the optical pulse having a plurality of wavelengths generated by the forward bias applying unit 42 and the reverse bias applying unit 44 is provided. Only a light pulse having a desired wavelength can be transmitted and incident on the photoconductive antenna 50, and a terahertz wave having a desired wavelength can be efficiently generated.

  In addition, since the second cladding layer 18 has a plurality of convex portions 48 toward the quantum well layer 32 side, a Bragg reflection mirror that reflects only a light pulse of a specific wavelength can be configured. Only a light pulse having a desired wavelength is guided to the photoconductive antenna 50, and a terahertz wave having a desired wavelength can be efficiently generated.

  Moreover, by applying a reverse bias voltage to the photoconductive antenna 50, the acceleration of the photocarrier increases. Therefore, the intensity of the terahertz wave emitted from the photoconductive antenna 50 can be increased.

[Production method]
Next, a method for manufacturing the terahertz wave generator 1 according to the embodiment of the present invention will be described with reference to FIGS. 3A to 3F.
3A, 3B, and 3C are schematic cross-sectional views taken along line AA in FIG. 1 for explaining the manufacturing process of the terahertz wave generation device. 3D, 3E, and 3F are schematic cross-sectional views taken along the line BB in FIG. 1 for explaining the manufacturing process of the terahertz wave generation device.

  First, the substrate 10 is prepared, and the buffer layer 12, the first cladding layer 14, the guide layer 30, the quantum well layer 32, and the barrier layer 34 are stacked on the substrate 10 as shown in FIG. 3A. The active layer 16 to be formed is epitaxially grown in this order. As a method for epitaxial growth, for example, MOCVD (Metal Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) method or the like can be used.

  Next, as shown in FIG. 3B, a groove 49 is formed in the guide layer 30 constituting the active layer 16. The groove 49 is formed by patterning using, for example, a photolithography technique and an etching technique.

  Thereafter, as shown in FIG. 3C, the second cladding layer 18 and the contact layer 22 are formed in this order on the guide layer 30 constituting the active layer 16 in which the groove 49 is formed, for example, MOCVD (Metal Organic). Epitaxial growth is performed using a chemical vapor deposition (MBE) method, an MBE (Molecular Beam Epitaxy) method, or the like.

  Next, as shown in FIG. 3D, a convex portion 48a serving as a waveguide of an optical pulse is formed in the second cladding layer 18 and the contact layer 22. The convex portion 48a is formed by patterning using, for example, a photolithography technique and an etching technique.

  Thereafter, as shown in FIG. 3E, the insulating layer 20 is formed on the second cladding layer 18 excluding the convex portions 48a. The insulating layer 20 is formed, for example, by patterning using a photolithography technique and an etching technique after coating with a spin coater or the like.

  Next, as illustrated in FIG. 3F, the second electrode 26 a is formed on the insulating layer 20 and the contact layer 22. The second electrode 26a is formed, for example, by forming it on the entire surface by a vacuum deposition method and then patterning it using a photolithography technique and an etching technique. In the present embodiment, the second electrode 26a of the forward bias applying unit 42 is described as an example, but the same method applies to the second electrode 26b of the reverse bias applying unit 44 and the second electrode 26c of the photoconductive antenna 50. Formed with.

Thereafter, the first electrode 24 is formed on the opposite side of the substrate 10 from the buffer layer 12 side. The first electrode 24 may be formed on the entire surface of the substrate 10 by, for example, a vacuum evaporation method. However, the first electrode 24 is formed on the entire surface in the same manner as the second electrode 26a, and then patterned by using a photolithography technique and an etching technique. It doesn't matter.
In addition, the formation order of the 1st electrode 24 and the 2nd electrode 26a is not specifically limited.

  Through the above steps, the active layer 16 including the quantum well layer 32 in which the optical pulse is guided is formed integrally with the optical pulse generation unit 40 and the photoconductive antenna 50, and is integrated on the same substrate 10, A terahertz wave generator 1 that efficiently generates a terahertz wave can be manufactured.

  In addition, the terahertz wave generator 1 of the present embodiment can be very downsized with an outer shape having a thickness of about 0.35 mm, a short side length of about 2 mm, and a long side length of about 10 mm. Since it can be mass-produced using a semiconductor facility, a significant cost reduction can be achieved.

Second Embodiment
Next, a terahertz wave generator 1a according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a schematic cross-sectional view showing the configuration of the terahertz wave generation device according to the second embodiment of the present invention.
Hereinafter, the terahertz wave generator 1a according to the second embodiment will be described focusing on differences from the terahertz wave generator 1 of the first embodiment described above. Moreover, the same code | symbol is attached | subjected to the same structure and the description is abbreviate | omitted about the same matter.

As shown in FIG. 4, the terahertz wave generator 1a according to the second embodiment has a different configuration of the distributed Bragg reflector 46a.
The distributed Bragg reflector 46 a in the terahertz wave generator 1 a includes the first cladding layer 14, the quantum well layer 32 constituting the active layer 16, and the second cladding layer 18. The second cladding layer 18 has a plurality of grooves 49a that open to the side opposite to the quantum well layer 32 side. Since the groove portions 49a of the second cladding layer 18 are periodically arranged, it can function as a diffraction grating and selectively reflect light of a specific wavelength. Therefore, it is possible to transmit only an optical pulse having a desired wavelength from among the optical pulses having a plurality of wavelengths generated by the forward bias applying unit 42 and the reverse bias applying unit 44 and to enter the photoconductive antenna 50.

The width dimension L3 of the guide layer 30 and the second cladding layer 18 of the active layer 16, the refractive index n of the guide layer 30 and the second cladding layer 18 is the same as in _{3.5, (m × λ 0/} 4 From xn), when the diffraction order m is 1 and the wavelength λ ₀ of the desired light is 800 nm, it becomes 57 nm as in L1 of the first embodiment. Furthermore, the width L4 of the grooves 49a of the guide layer 30 and the second cladding layer 18 of the active layer 16, since the groove portion 49a is air, a _{(m × λ 0/4)} . Therefore, if the diffraction order m is 1, and the desired wavelength λ ₀ is 800 nm, L4 is 200 nm. Therefore, the groove portions 49a are arranged with the width dimensions L3 and L4 at intervals of 57 nm and 200 nm.

  By adopting such a configuration, it is possible to configure a Bragg reflection that reflects only an optical pulse having a specific wavelength. Therefore, in the optical pulse generated by the optical pulse generator 40a, only an optical pulse having a desired wavelength is emitted. A terahertz wave having a desired wavelength can be generated by being guided to the conductive antenna 50.

[Imaging equipment]
Next, an imaging apparatus 100 including the terahertz wave generation device 1 according to the embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a block diagram showing a configuration of the imaging apparatus according to the embodiment of the present invention. FIG. 6 is a plan view showing a terahertz wave detection unit of the imaging apparatus shown in FIG. FIG. 7 is a graph showing the spectrum of the target in the terahertz band. FIG. 8 is a diagram of an image showing the distribution of the substances A, B, and C of the object.

  As illustrated in FIG. 5, the imaging apparatus 100 includes a terahertz wave generation apparatus 1 that generates a terahertz wave, and a terahertz wave detection unit that detects the terahertz wave that is emitted from the terahertz wave generation apparatus 1 and transmitted or reflected by the object 110. 120, and an image forming unit 130 that generates an image of the object 110, that is, image data, based on the detection result of the terahertz wave detection unit 120. Note that the description of the terahertz wave generator 1 is omitted.

  Further, as shown in FIG. 6, the terahertz wave detection unit 120 includes a filter 150 that transmits a terahertz wave having a target wavelength, and a detection unit 170 that detects the terahertz wave having the target wavelength that has passed through the filter 150. Use what you have. Further, as the detection unit 170, for example, a detection unit that converts a terahertz wave into heat and detects it, that is, a unit that can convert a terahertz wave into heat and detect energy (intensity) of the terahertz wave is used. Examples of such a detection unit include a pyroelectric sensor and a bolometer. Needless to say, the terahertz wave detection unit 120 is not limited to the above-described configuration.

The filter 150 includes a plurality of pixels (unit filter units) 160 that are two-dimensionally arranged. That is, the pixels 160 are arranged in a matrix.
Each pixel 160 has a plurality of regions that transmit terahertz waves having different wavelengths, that is, a plurality of regions that have different wavelengths of terahertz waves that pass (hereinafter also referred to as “passing wavelengths”). In the illustrated configuration, each pixel 160 includes a first region 161, a second region 162, a third region 163, and a fourth region 164.

  The detection unit 170 also includes a first unit detection provided corresponding to the first region 161, the second region 162, the third region 163, and the fourth region 164 of each pixel 160 of the filter 150. A unit 171, a second unit detector 172, a third unit detector 173, and a fourth unit detector 174. Each first unit detector 171, each second unit detector 172, each third unit detector 173, and each fourth unit detector 174, respectively, includes a first region 161 of each pixel 160, The terahertz wave that has passed through the second region 162, the third region 163, and the fourth region 164 is converted into heat and detected. Thereby, in each of the pixels 160, terahertz waves having four target wavelengths can be reliably detected.

Next, a usage example of the imaging apparatus 100 will be described.
First, it is assumed that the object 110 to be subjected to spectral imaging is composed of three substances A, B, and C. The imaging apparatus 100 performs spectral imaging of the object 110. Here, as an example, the terahertz wave detection unit 120 detects a terahertz wave reflected from the object 110.
In each pixel 160 of the filter 150 of the terahertz wave detection unit 120, the first region 161 and the second region 162 are used.

  Further, the transmission wavelength of the first region 161 is λ1, the transmission wavelength of the second region 162 is λ2, the intensity of the component of wavelength λ1 of the terahertz wave reflected by the object 110 is α1, and the intensity of the component of wavelength λ2 is When α2 is set, the difference (α2−α1) between the intensity α2 and the intensity α1 can be distinguished from each other among the substance A, the substance B, and the substance C, so that the transmission wavelength λ1 of the first region 161 and The pass wavelength λ2 of the second region 162 is set.

As shown in FIG. 7, in the substance A, the difference (α2−α1) between the intensity α2 of the component with wavelength λ2 of the terahertz wave reflected by the object 110 and the intensity α1 of the component with wavelength λ1 is a positive value.
In the substance B, the difference (α2−α1) between the intensity α2 and the intensity α1 is zero.
Further, in the substance C, the difference (α2−α1) between the intensity α2 and the intensity α1 is a negative value.

  When spectral imaging of the object 110 is performed by the imaging apparatus 100, first, a terahertz wave is generated by the terahertz wave generation apparatus 1, and the object 110 is irradiated with the terahertz wave. Then, the terahertz wave reflected by the object 110 is detected by the terahertz wave detection unit 120 as α1 and α2. This detection result is sent to the image forming unit 130. Note that the irradiation of the terahertz wave to the object 110 and the detection of the terahertz wave reflected by the object 110 are performed on the entire object 110.

  In the image forming unit 130, based on the detection result, the intensity α2 of the component of the wavelength λ2 of the terahertz wave that has passed through the second region 162 of the filter 150 and the wavelength λ1 of the terahertz wave that has passed through the first region 161 are detected. The difference (α2−α1) of the intensity α1 of the component is obtained. Then, in the object 110, a part where the difference is a positive value is determined as a substance A, a part where the difference is zero is determined as a substance B, and a part where the difference is a negative value is determined as a substance C.

  Further, the image forming unit 130 creates image data of an image indicating the distribution of the substances A, B, and C of the object 110 as shown in FIG. This image data is sent from the image forming unit 130 to a monitor (not shown), and an image showing the distribution of the substances A, B, and C of the object 110 is displayed on the monitor. In this case, for example, the region in which the substance A is distributed in the object 110 is black (indicated by cross lines in FIG. 8), the region in which the substance B is distributed is gray (indicated by diagonal lines in FIG. 8), and the region in which the substance C is distributed. Are displayed in white. As described above, the imaging apparatus 100 can simultaneously identify each substance constituting the object 110 and measure the distribution of each substance.

  The use of the imaging apparatus 100 is not limited to the above, and for example, a terahertz wave is irradiated to a person, a terahertz wave transmitted or reflected by the person is detected, and the image forming unit 130 performs processing. Thus, it is possible to determine whether or not the person has a handgun, a knife, an illegal drug, or the like.

[camera]
Next, the camera 200 provided with the terahertz wave generator 1 according to the embodiment of the present invention will be described with reference to FIGS. 9 and 10.
FIG. 9 is a block diagram showing the configuration of the camera according to the embodiment of the present invention. FIG. 10 is a perspective view showing the configuration of the camera according to the embodiment of the present invention.
Hereinafter, the embodiment of the camera 200 will be described focusing on the differences from the above-described embodiment of the imaging apparatus 100, and the detailed description of the same matters will be omitted.

  As shown in FIGS. 9 and 10, the camera 200 detects the terahertz wave that is emitted from the terahertz wave generator 1 that generates the terahertz wave and is reflected from the object 210 and is reflected from the object 210. Part 220. These units are housed in a housing 250 of the camera 200. Further, the terahertz wave reflected by the object 210 is converged (imaged) on the terahertz wave detection unit 220, and the terahertz wave generated by the terahertz wave generator 1 is emitted to the outside of the housing 250. A window 270 is provided. The lens 260 and the window portion 270 are made of a member such as silicon, quartz, or polyethylene that transmits and refracts terahertz waves. Note that the window 270 may have a configuration in which an opening is simply provided like a slit.

Next, a usage example of the camera 200 will be described.
When imaging the object 210 with the camera 200, first, the terahertz wave is generated by the terahertz wave generator 1, and the object 210 is irradiated with the terahertz wave. Then, the terahertz wave reflected by the object 210 is converged (imaged) on the terahertz wave detection unit 220 by the lens 260 and detected. This detection result is sent to and stored in the storage unit 230. The irradiation of the terahertz wave to the object 210 and the detection of the terahertz wave reflected by the object 210 are performed on the entire object 210. The detection result can be transmitted to an external device such as a personal computer. In the personal computer, each process can be performed based on the detection result.

[Measurement equipment]
Next, a measurement device 300 including the terahertz wave generation device 1 according to the embodiment of the present invention will be described with reference to FIG.
FIG. 11 is a block diagram showing the configuration of the measuring apparatus according to the embodiment of the present invention.
Hereinafter, the embodiment of the measurement apparatus 300 will be described focusing on the differences from the above-described embodiment of the imaging apparatus 100, and detailed description of the same matters will be omitted.

  As shown in FIG. 11, the measurement device 300 includes a terahertz wave generation device 1 that generates a terahertz wave, and a terahertz wave detection unit that detects the terahertz wave that is emitted from the terahertz wave generation device 1 and transmitted or reflected by the object 310. 320 and a measurement unit 330 that measures the object 310 based on the detection result of the terahertz wave detection unit 320.

Next, a usage example of the measuring apparatus 300 will be described.
When spectroscopic measurement of the object 310 is performed by the measuring apparatus 300, first, the terahertz wave is generated by the terahertz wave generating apparatus 1, and the object 310 is irradiated with the terahertz wave. Then, the terahertz wave transmitted or reflected by the object 310 is detected by the terahertz wave detection unit 320. This detection result is sent to the measurement unit 330. Note that the irradiation of the terahertz wave to the object 310 and the detection of the terahertz wave transmitted or reflected by the object 310 are performed on the entire object 310.

  In the measurement unit 330, from the detection result, similarly to the terahertz wave detection unit 120 of the imaging device 100 illustrated in FIG. 6, the first region 161, the second region 162 of the filter 150 in the terahertz wave detection unit 320, The intensities of the terahertz waves that have passed through the third region 163 and the fourth region 164 are grasped, and the components of the object 310 and the distribution thereof are analyzed.

[Terahertz spectrometer]
Next, a terahertz spectroscopic analysis apparatus 300a as a measurement apparatus 300 including the terahertz wave generation apparatus 1 according to the embodiment of the present invention will be described with reference to FIG.
FIG. 12 is a block diagram illustrating a configuration of a terahertz spectroscopic analysis apparatus as a measurement apparatus according to an embodiment of the present invention.
Hereinafter, the embodiment of the terahertz spectroscopy analyzer 300a will be described with a focus on differences from the above-described embodiment of the measurement apparatus 300, and detailed description of the same matters will be omitted.

  As shown in FIG. 12, the terahertz spectrometer 300a includes a terahertz wave generator 1 that emits a terahertz wave and an optical pulse, a terahertz wave detector 320a that detects a terahertz wave that has passed through the object 310a, and terahertz wave detection. A delay optical system 350 that changes the optical path length of the optical pulse from the terahertz wave generator 1 to the terahertz wave detector 320a. I have.

Next, a usage example of the terahertz spectrometer 300a will be described.
When performing spectroscopic measurement of the object 310a by the terahertz spectrometer 300a, first, a terahertz wave and an optical pulse are emitted from the terahertz wave generator 1.
The terahertz wave emitted from the terahertz wave generation device 1 is collected by the curved mirror 340a and applied to the object 310a. The terahertz wave that has passed through the object 310a is again collected by the curved mirror 340b and is incident on the terahertz wave detection unit 320a.

The light pulse emitted from the terahertz wave generation device 1 is reflected by the reflection mirror 360a and is incident on the delay optical system 350 that changes the optical path length of the light pulse from the terahertz wave generation device 1 to the terahertz wave detection unit 320a. The delay optical system 350 includes four reflection mirrors 360b, 360c, 360d, and 360e, and changes the optical path length by adjusting the interval between the four reflection mirrors 360b, 360c, 360d, and 360e, and the terahertz wave detection unit 320a. The arrival time can be delayed.
The light pulse that has passed through the delay optical system 350 is reflected by the reflection mirror 360f and is incident on the terahertz wave detection unit 320a.

  In this embodiment, the delay optical system 350 uses four reflection mirrors 360b, 360c, 360d, and 360e. However, the present invention is not limited to this, and has two, three, or five or more configurations. There may be.

  The terahertz wave detection unit 320a is configured by a photoconductive antenna. When a terahertz wave that has passed through the object 310a is incident on the terahertz wave detection unit 320a, an electric field is generated in the antenna unit (not shown) of the terahertz wave detection unit 320a, and an optical pulse with a delayed time to reach this part is generated. When irradiated, a photocurrent according to the electric field intensity of the terahertz wave flows. By calculating the current value of the photocurrent, that is, the value of the electric field intensity, based on a predetermined theoretical formula in the measurement unit 330a, the electrical characteristics, the impurity concentration, and the like of the object 310a can be obtained. These measured values are displayed on a display (not shown) as necessary.

  Further, the electric field intensity of the terahertz wave transmitted through the object 310a detected by the terahertz wave detection unit 320a is measured while changing the delay time of the optical pulse emitted from the terahertz wave generation device 1 to reach the terahertz wave detection unit 320a. By doing so, time series terahertz spectroscopy becomes possible.

  As described above, the terahertz wave generation devices 1 and 1a, the imaging device 100, the camera 200, the measurement device 300, and the terahertz spectroscopic analysis device 300a of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited thereto. However, the configuration of each part can be replaced with any configuration having a similar function. In addition, any other component may be added to the present invention. Moreover, you may combine each embodiment suitably.

  DESCRIPTION OF SYMBOLS 1,1a ... Terahertz wave generator, 10 ... Board | substrate, 12 ... Buffer layer, 14 ... 1st clad layer, 16 ... Active layer, 18 ... 2nd clad layer, 20 ... Insulating layer, 22 ... Contact layer, 24 ... 1st 1 electrode, 26a, 26b, 26c ... 2nd electrode, 28a ... 1st side surface, 28b ... 2nd side surface, 30 ... Guide layer, 32 ... Quantum well layer, 34 ... Barrier layer, 40 ... Optical pulse generation part, 42 ... Forward bias applying unit, 44: reverse bias applying unit, 46: distributed Bragg reflector, 48, 48a ... convex portion, 49, 49a ... groove, 50 ... photoconductive antenna, 52a, 52b, 52c ... power source, 100 ... imaging device , 200 ... camera, 300 ... measuring device, 300a ... terahertz spectroscopy analyzer.

Claims (8)

An optical pulse generator including a quantum well layer and generating an optical pulse;
A photoconductive antenna including the quantum well layer;
The optical pulse generator is
A forward bias application unit to which a forward bias voltage is applied;
A reverse bias application unit to which a reverse bias voltage is applied;
A distributed Bragg reflector that reflects a portion of the light guided through the quantum well layer,
The photoconductive antenna is
A terahertz wave generating apparatus, which receives a light pulse transmitted through the distributed Bragg reflector and generates a terahertz wave. The distributed Bragg reflector has a first cladding layer, the quantum well layer, and a second cladding layer,
2. The terahertz wave generating device according to claim 1, wherein the second cladding layer has a plurality of convex portions toward the quantum well layer. The distributed Bragg reflector has a first cladding layer, the quantum well layer, and a second cladding layer,
2. The terahertz wave generating device according to claim 1, wherein the second cladding layer has a plurality of grooves that are opened to a side opposite to the quantum well layer side.   The terahertz wave generation device according to any one of claims 1 to 3, wherein a reverse bias voltage is applied to the photoconductive antenna. The terahertz wave generator according to any one of claims 1 to 4,
A terahertz wave detector that detects a terahertz wave that is emitted from the terahertz wave generator and is transmitted or reflected by the object;
An image forming unit that generates an image of an object based on a detection result of the terahertz wave detection unit;
An imaging apparatus comprising: The terahertz wave generator according to any one of claims 1 to 4,
A terahertz wave detector that detects the terahertz wave that is emitted from the terahertz wave generator and reflected by the object;
A storage unit for storing a detection result of the terahertz wave detection unit;
A camera characterized by comprising: The terahertz wave generator according to any one of claims 1 to 4,
A terahertz wave detector that detects a terahertz wave that is emitted from the terahertz wave generator and is transmitted or reflected by the object;
A measurement unit that measures an object based on a detection result of the terahertz wave detection unit;
A measuring device comprising: The terahertz wave detection unit is irradiated with a light pulse emitted from the terahertz wave generator,
The measurement apparatus according to claim 7, further comprising a delay optical system that changes an optical path length of an optical pulse from the terahertz wave generation apparatus to the terahertz wave detection unit.

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