WO2011001521A1 - Terahertz light generating device and method - Google Patents

Terahertz light generating device and method Download PDF

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Publication number
WO2011001521A1
WO2011001521A1 PCT/JP2009/062040 JP2009062040W WO2011001521A1 WO 2011001521 A1 WO2011001521 A1 WO 2011001521A1 JP 2009062040 W JP2009062040 W JP 2009062040W WO 2011001521 A1 WO2011001521 A1 WO 2011001521A1
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Prior art keywords
terahertz light
light
terahertz
frequency
refractive index
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PCT/JP2009/062040
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French (fr)
Japanese (ja)
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隆信 樋口
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パイオニア株式会社
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Priority to PCT/JP2009/062040 priority Critical patent/WO2011001521A1/en
Publication of WO2011001521A1 publication Critical patent/WO2011001521A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • G02F1/3534—Three-wave interaction, e.g. sum-difference frequency generation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2202/00—Materials and properties
    • G02F2202/32—Photonic crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00—Function characteristic
    • G02F2203/13—Function characteristic involving THZ radiation

Definitions

  • the present invention relates to a variable frequency terahertz light generating apparatus and method using a one-dimensional photonic crystal.
  • electromagnetic waves also referred to as terahertz light
  • terahertz light in the terahertz frequency band of 0.1 to 100 THz correspond to vibrational energy such as lattice vibration, intramolecular vibration, and intermolecular interaction.
  • Information specific to a substance such as a polymer can be obtained.
  • terahertz light applications in various fields are conceivable, and there is great interest in the generation and control of terahertz light, and many terahertz light generators have been developed.
  • a terahertz light generator there is a variable frequency type device using a semiconductor laser as a pump light source and a signal light source (see Patent Document 1).
  • the nonlinear crystal in order to solve the problem that the output of the terahertz light is low, in order to reduce the optical path cross-sectional area in the optical nonlinear crystal such as GaP, the nonlinear crystal has a waveguide structure or pump light.
  • the signal light is condensed by an optical lens so that the minimum beam radius becomes the required optical cross-sectional area.
  • a photonic crystal is known as a crystal in which two kinds of substances having different dielectric constants (refractive indices) are artificially arranged alternately one-dimensionally, two-dimensionally or three-dimensionally.
  • dielectric constants reffractive indices
  • the wave travels through the material while feeling the periodicity of the dielectric constant, similar to the situation where electrons pass through a crystal in which atoms are periodically arranged.
  • the dispersion relationship of electromagnetic waves in a photonic crystal is called a photonic band, and it corresponds to a photonic band gap just as an electron with an energy corresponding to the electronic band gap cannot exist in the crystal. Frequency electromagnetic waves cannot exist in the photonic crystal. Research on control technology of photonic crystals having such properties has been made.
  • terahertz light generation using a photonic crystal is also performed.
  • a terahertz light source including a resonator structure including a one-dimensional photonic crystal having a nonlinear optical material defect portion therein and a mirror sandwiching the defect portion has been proposed (see Patent Document 2).
  • terahertz light corresponding to the frequency difference of a femtosecond pulse laser multiple longitudinal modes
  • terahertz light having a wavelength corresponding to the resonance wavelength of the one-dimensional photonic crystal Only take out.
  • an optical device in which an impurity structure made of a nonlinear crystal is provided between the first and second photonic crystal structures (see Patent Document 3).
  • this optical device by changing the thickness of the nonlinear optical crystal and the surface state of the adjacent photonic crystal, the spectrum and intensity of the terahertz light corresponding to the difference between the many longitudinal mode frequencies of the incident femtosecond pulse laser can be changed. adjust.
  • a terahertz light generating element having a wedge structure in which the spectral component of the emitted terahertz light is made of a nonlinear optical crystal that varies with thickness and has a continuously varying thickness. This is to emit terahertz light by femtosecond pulse laser irradiation of incident pulsed light, and by changing the irradiation position of the pulsed light, the thickness of the nonlinear optical crystal is varied, and the generated broadband terahertz is generated. The wavelength of light is changed.
  • Patent Document 1 it is difficult and expensive to form a waveguide structure, and there is a problem that the optical system becomes complicated when a condensing optical system is used.
  • Patent Document 3 since the thickness of the nonlinear optical crystal and the surface state of the adjacent photonic crystal are changed, a plurality of independent devices are produced, and the device is not changed. The spectrum and intensity of terahertz light cannot be adjusted, and there is a problem that terahertz light with excellent monochromaticity cannot be extracted as long as a femtosecond pulse laser is used.
  • Patent Document 4 As long as a femtosecond pulse laser is used, terahertz light having excellent monochromaticity cannot be extracted, and a resonator structure such as a one-dimensional photonic crystal for enhancing wavelength selection is used. There are problems that are difficult to use.
  • the present invention is an example of a problem to deal with such a problem. That is, it is an example of an object of the present invention to provide a small and high intensity variable frequency terahertz light generating apparatus and method.
  • a terahertz light generating device is a terahertz light generating device that emits terahertz band electromagnetic waves upon incidence of laser light, and is a one-dimensional photonic in which dielectric layers of high refractive index and low refractive index are alternately stacked.
  • An amplification optical element having a defect layer made of a non-linear optical crystal in the periodic direction of the crystal, a rotation axis passing through the defect layer and perpendicular to the periodic direction of the one-dimensional photonic crystal, and the amplification
  • a rotation mechanism that rotates an optical element around the rotation axis, and at least two laser beams having frequencies close to each other are incident in a periodic direction of the one-dimensional photonic crystal, and an incident angle is adjusted by the rotation mechanism. It has a control device which changes the frequency of the electromagnetic wave radiated by changing it relatively.
  • the terahertz light can be generated by collinear phase matching in which the laser light and the terahertz light are arranged on the same optical axis.
  • the laser light includes a light source that uses two laser lights having different wavelengths as pump light, and has a frequency corresponding to a difference in frequency between the two pump lights. Can be generated.
  • the control device includes a light source wavelength rough adjustment unit that changes the frequency of at least one of the two pump lights, and the frequency of the terahertz light is adjusted by the pump light having the frequency changed. It can be changed.
  • the control device includes a rotation control unit that drives the rotation mechanism and rotates the amplification optical element according to the frequency of the pump light whose frequency has been changed. be able to.
  • the terahertz light generator includes a sensor that detects the intensity of the generated terahertz light, and the rotation control unit finely adjusts the incident angle of the laser light so that the intensity of the generated terahertz light is maximized. Can be.
  • the nonlinear optical crystal can be GaP, ZnTe, GaSe, or DAST (4-dimethylamino-N-methyl-4-stilbazolium-tosylate).
  • the high refractive index and low refractive index dielectric layers of the one-dimensional photonic crystal may be fused silica glass and polyethylene.
  • the frequency difference of the laser light may be in a terahertz frequency band of 0.1 to 100 THz.
  • the terahertz light generation method of the present invention is a terahertz light generation method that emits terahertz band electromagnetic waves upon incidence of laser light, and is a one-dimensional photonic in which dielectric layers of high refractive index and low refractive index are alternately stacked.
  • the step of preparing an amplifying optical element having a defect layer made of a nonlinear optical crystal in the periodic direction of the crystal is the same as the laser light having at least two frequencies close to each other in the periodic direction of the one-dimensional photonic crystal.
  • a step of making it incident on the optical axis a step of changing the frequency of at least one of the laser beams, and a rotation axis extending through the defect layer in a direction perpendicular to the periodic direction of the one-dimensional photonic crystal.
  • the frequency of the emitted electromagnetic wave is changed. Characterized in that it comprises a Mel coarse step.
  • the terahertz light generator according to the present invention can provide a small and high-intensity terahertz light source that can take advantage of the wavelength variability that is characteristic of the difference frequency generation of terahertz light using a nonlinear optical crystal.
  • a non-linear optical crystal defect layer disposed in the middle of a periodic direction of a one-dimensional photonic crystal in which dielectric layers having a high refractive index and a low refractive index are alternately stacked, and the defect layer are sandwiched Since the amplifying optical element having a resonator structure including a mirror is rotatable, terahertz light corresponding to the difference in frequency between two pump lights having different wavelengths incident on the amplifying optical element is generated (difference frequency).
  • the terahertz light having a wavelength corresponding to the resonance wavelength of the one-dimensional photonic crystal can be extracted with high accuracy by the rotation of the amplification optical element, and the terahertz light having a desired wavelength is amplified. Can do. Thereby, the quality of output terahertz light can be improved.
  • FIG. 1 is a schematic partial cross-sectional view of an amplification optical element of a terahertz light generator according to an embodiment of the present invention. It is a flowchart which shows an example of the terahertz light generation method by the terahertz light generator concerning embodiment of this invention. It is sectional drawing of the optical element for amplification of the terahertz light generator concerning embodiment of this invention. It is a graph which shows the change of the terahertz light intensity with respect to the terahertz light frequency at the time of changing an incident angle in the terahertz light generator concerning other embodiment of this invention.
  • FIG. 1 is a schematic diagram of a terahertz light generator according to an embodiment of the present invention.
  • the terahertz light generation device 11 of the present embodiment includes an amplification optical element 12 and a rotation mechanism 13 that holds the amplification optical element.
  • FIG. 2 is a schematic cross-sectional view of a one-dimensional photonic crystal as the amplification optical element 12.
  • the one-dimensional photonic crystal of the amplifying optical element 12 is a multilayer in which a plurality of pairs of high refractive index dielectric layers H and low refractive index dielectric layers L are alternately stacked. It has a structure of M1 and M2, and a non-linear optical crystal layer having a predetermined film thickness is provided as a defect layer 14 between them (central part).
  • the high refractive index and low refractive index dielectric layers H and L (high refractive index layer and low refractive index layer) of the one-dimensional photonic crystal are, for example, fused silica glass and polyethylene.
  • the nonlinear optical crystal of the defect layer 14 has a high second-order nonlinear optical coefficient, such as GaP, ZnTe, GaSe as an inorganic material, or DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) as an organic material.
  • the amplifying optical element 12 includes dielectric layers having high refractive index (n H ) and low refractive index (n L ⁇ n H ) (optical film thicknesses: n H ⁇ d H and n L ⁇ d L, respectively).
  • the defect layer 14 made of a nonlinear optical crystal is interposed in the film thickness direction (period direction) of the one-dimensional photonic crystal laminated alternately. Composed.
  • the multilayers M1 and M2 constitute a resonator corresponding to a dielectric multilayer mirror having a high reflectance, and a nonlinear optical crystal is provided in the resonator.
  • the amplitude of the photoelectric field in the defect layer is larger than the amplitude of the incident photoelectric field.
  • (n H / n L ) is a refractive index ratio between the high refractive index layer and the low refractive index layers H and L. Therefore, since the defect layer is a nonlinear optical crystal, the nonlinear optical effect (terahertz light generated by difference frequency) is greatly amplified due to the amplified light intensity.
  • the rotation mechanism 13 of the terahertz light generator 11 has a rotation axis O extending through a defect layer 14 in a direction perpendicular to the periodic direction of the one-dimensional photonic crystals M1 and M2, and for amplification.
  • a rotation stage 131 for rotating the optical element 12 around the rotation axis O is included.
  • the rotation mechanism 13 includes a motor that rotates or rotates an electrically controllable rotation stage 131 and a drive mechanism (not shown).
  • the terahertz light generator 11 shown in FIG. 1 includes two variable wavelength laser light sources 21 and a fixed wavelength laser light source 22 that use two laser lights having different wavelengths as pump light.
  • These excitation laser light sources 21 and 22 are single mode lasers such as DFB and DBR.
  • the amplification optical element 12 and the laser light source 21 are arranged so that the optical axis of the injection pump light of one laser light source 21 passes through the rotation axis O of the one-dimensional photonic crystals M1 and M2, and the other laser light source 22 is disposed.
  • the pump light emitted from the light beam is reflected by the half mirror 23 arranged on the optical axis, and both pump lights are incident on the amplification optical element 12 on the same optical axis.
  • the terahertz light generation device 11 shown in FIG. 1 includes a control device 31 connected to a variable wavelength laser light source 21, and the control device 31 functions as a light source wavelength rough adjustment unit that changes the frequency of the pump light.
  • the pump light ( ⁇ 1 ⁇ ⁇ ) whose frequency is changed by the control device 31 slightly changes the frequency of the output terahertz light.
  • the control device 31 of the terahertz light generation device 11 shown in FIG. 1 is further connected to the rotation mechanism 13, and controls and drives the rotation mechanism 13 in accordance with the frequency ( ⁇ 1 ⁇ ⁇ ) of the pump light whose frequency has been changed. It functions as a rotation control unit (light source wavelength fine tuning unit) that rotates the nick crystals M1 and M2.
  • the terahertz light generation device 11 shown in FIG. 1 includes a sensor 32 that is connected to the control device 31 and detects the intensity of the generated terahertz light.
  • the sensor 32 is disposed on the optical axis downstream of the half mirror 24 that branches the terahertz light from the optical axis of the pump light and terahertz light opposite to the pump light of the amplification optical element 12.
  • the control device 31 as the rotation control unit further finely adjusts the relative incident angle ⁇ of the pump light ( ⁇ 1, ⁇ 2) by the rotation mechanism 13 so that the intensity of the terahertz light detected by the sensor 32 is maximized.
  • terahertz light generator A small piece of zinc telluride (ZnTe) having a 10 mm square and a thickness of 1 mm is used as the nonlinear optical crystal of the amplification optical element of the terahertz light generator.
  • ZnTe zinc telluride
  • Fused silica glass is used for the high refractive index layer, and polyethylene is used for the low refractive index layer.
  • the thickness is 19 microns and 27 microns, respectively.
  • the frequency of the terahertz light to be amplified is 2 THz when the pump light is vertically incident on the amplification optical element.
  • a terahertz light generator is assembled by installing a rotating stage, an amplification optical element, a light source, etc. on a vibration isolator.
  • the optical element for amplification is mounted on a vibration isolation table via a stepping motor driven automatic rotation stage such as SGSP-40YAW manufactured by Sigma Kogyo.
  • the light source includes, for example, a high-power DFB laser diode (single-mode fixed wavelength, output of 100 mW or more) from Frankfurt Laser (Germany) as a fixed wavelength laser, and a high-power Littrow external cavity tunable laser Tiger from Sacher Lasertechnik (Germany). (Variable wavelength range 750 nm to 1070 nm, output 100 mW or more). Two pump lights emitted from these two light sources are arranged on the same axis using an optical mirror as appropriate, and guided to the amplification optical element.
  • the optical system is adjusted so that two pump lights are incident collinearly in the periodic direction of the one-dimensional photonic crystal of the prepared amplification optical element.
  • the output wavelength of the wavelength tunable laser is set (wavelength setting of the wavelength tunable laser: S1) so that terahertz light having a desired frequency is obtained, and coarse adjustment is performed.
  • the incident angle of the pump light incident on the amplification optical element is controlled by rotating the automatic rotation stage to a predetermined angle (element incident angle adjustment: S2).
  • the output wavelength of the fixed wavelength laser is 800.0 nm
  • the output wavelength of the wavelength tunable laser is set to 804.8 nm and the incident angle is 45 degrees. Adjust the automatic rotation stage so that
  • the fixed wavelength laser and the wavelength tunable laser are turned on (laser ON: S3).
  • the generated terahertz light is amplified by a one-dimensional photonic crystal structure, and is extracted coaxially with the pump light and opposite to the pump light.
  • the intensity of the terahertz light is detected by a light receiving optical system such as a silicon bolometer (terahertz light output measurement: S4), and it is determined whether or not the terahertz light intensity is maximum (maximum terahertz light output: S5).
  • a light receiving optical system such as a silicon bolometer (terahertz light output measurement: S4)
  • the automatic rotation stage is driven to roughly adjust and finely adjust the incident angle of the pump light.
  • the pump light may be condensed by an optical lens and made incident on the amplification optical element.
  • ⁇ Specific configuration example of one-dimensional photonic crystal of terahertz light generator> An example of the configuration of the amplification optical element and the incident angle control with respect to the frequency of the terahertz light to be amplified in the amplification optical element is given.
  • the high refractive index layer of the one-dimensional photonic crystal was fused silica glass (refractive index 1.96), and the low refractive index layer was polyethylene (refractive index 1.37).
  • zinc telluride (ZnTe) was used as a nonlinear optical crystal for generating terahertz light.
  • FIG. 4 shows a cross-sectional view of the amplification optical element 42 of the terahertz light generator.
  • Five pairs of low refractive index layer / high refractive index layer are stacked in this order from the incident side of the pump light, then a nonlinear optical crystal is used as a defect layer, and then five sets of high refractive index layer / low refractive index layer are stacked in this order.
  • an amplification optical element was configured.
  • the thickness of the fused silica glass that is the high refractive index layer is 19.1 microns
  • the thickness of the polyethylene that is the low refractive index layer is 27.4 microns
  • the thickness of zinc telluride (ZnTe) that is a nonlinear optical crystal The thickness was 1 mm.
  • H fused silica glass
  • L is polyethylene
  • 44 is ZnTe.
  • FIG. 5 is a graph showing changes in the terahertz light intensity with respect to the terahertz light frequency when the incident angle is changed to 0 degrees, 30 degrees, and 45 degrees.
  • the terahertz light intensity is periodically amplified with respect to the terahertz light frequency, there is a frequency having a high amplification factor with respect to the incident angle.
  • the incident angle is 0 degree
  • 2.06 THz terahertz light is efficiently amplified.
  • the amplification efficiency is good for 2.15 THz terahertz light when the incident angle is 30 degrees, and 2.24 THz terahertz light when the incident angle is 45 degrees.
  • the output wavelength of the fixed wavelength laser is 800.0 nm
  • the output wavelength of the tunable laser is set to 804.8 nm
  • the automatic rotation stage is adjusted so that the incident angle is 45 degrees.
  • 2.24 THz terahertz light can be generated.
  • the terahertz light generator is the same as the above configuration example except that gallium phosphide (GaP) is used for the nonlinear optical crystal and a fixed wavelength laser and a wavelength tunable laser having a light source wavelength of about 990 nm are used.
  • GaP gallium phosphide
  • the organic nonlinear optical crystal 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) is used as the nonlinear optical crystal, and the wavelength of the light source is variable from 780 to 800 nm or 1064 nm.
  • DAST dimethylamino-N-methyl-4-stilbazolium tosylate
  • the above configuration example is the same except that a laser is used.
  • Organic nonlinear optical crystals generally have high nonlinear optical coefficients and have a small difference in refractive index between the light wave band and the terahertz wave band. Therefore, organic nonlinear optical crystals are materials that are expected to generate high-efficiency and broadband terahertz light due to difference frequency generation. .
  • the optical filter 33 is disposed between the amplification optical element 12 and the downstream half mirror 24 to block the pump light, and the terahertz light is generated. It can also be set as the structure which permeate

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

A terahertz light generating device of a variable frequency type having a small size and generating a strong light.  A method for generating a terahertz light is also disclosed.  The terahertz light generating device emits an electromagnetic wave in the terahertz band when receiving a laser beam.  The terahertz light generating device includes a controller which comprises an amplifying optical element and a rotating mechanism.  The amplifying optical element is composed of linear photonic crystals in which dielectric layers of high refractive index and those of low refractive index are alternated and a defect layer of a nonlinear optical crystal is interposed in the periodicity direction of the linear photonic crystals.  The rotating mechanism has a rotary shaft extending through the defect layer perpendicularly to the periodicity direction and rotates the amplifying optical element around the rotary shaft.  The controller causes at least two laser beams having frequencies approximate to each other to enter the linear photonic crystal in the periodicity direction and relatively varies the angle of incidence by means of the rotating mechanism so as to vary the frequency of the emitted electromagnetic wave.

Description

テラヘルツ光発生装置及び方法Terahertz light generation apparatus and method
　本発明は、１次元フォトニック結晶を用いた可変周波数型のテラヘルツ光発生装置及び方法に関する。 The present invention relates to a variable frequency terahertz light generating apparatus and method using a one-dimensional photonic crystal.
　従来から、０．１～１００ＴＨｚのテラヘルツ周波数帯域の電磁波（テラヘルツ光ともいう）は、格子振動、分子内振動、分子間相互作用などの振動エネルギーに相当することから、テラヘルツ光を利用してタンパク質、高分子などの物質固有の情報を得ることができる。物質分析以外にも種々の分野のテラヘルツ光応用が考えられ、テラヘルツ光の発生、制御には大きな関心が寄せられ、多くのテラヘルツ光発生装置が開発されている。たとえば、テラヘルツ光発生装置として、ポンプ光源と信号光源として半導体レーザを利用した可変周波数型のものがある（特許文献１、参照）。この装置においては、テラヘルツ光の出力が低いという問題を解決するために、ＧａＰなどの光非線形性結晶中の光路断面積を小さくするために、非線形性結晶を導波路構造にし、あるいは、ポンプ光と信号光を光学レンズで集光して、ビーム最小半径を必要な光断面積となるようにしている。 Conventionally, electromagnetic waves (also referred to as terahertz light) in the terahertz frequency band of 0.1 to 100 THz correspond to vibrational energy such as lattice vibration, intramolecular vibration, and intermolecular interaction. Information specific to a substance such as a polymer can be obtained. In addition to material analysis, terahertz light applications in various fields are conceivable, and there is great interest in the generation and control of terahertz light, and many terahertz light generators have been developed. For example, as a terahertz light generator, there is a variable frequency type device using a semiconductor laser as a pump light source and a signal light source (see Patent Document 1). In this device, in order to solve the problem that the output of the terahertz light is low, in order to reduce the optical path cross-sectional area in the optical nonlinear crystal such as GaP, the nonlinear crystal has a waveguide structure or pump light. The signal light is condensed by an optical lens so that the minimum beam radius becomes the required optical cross-sectional area.
　一方、フォトニック結晶は、誘電率（屈折率）の異なる２種類の物質を交互に１次元、２次元又は３次元と人工的に周期的に並べた結晶として知られている。フォトニック結晶に電磁波を入射させると、その波は誘電率の周期性を感じながら物質内を進むことになり、原子が周期的に並んだ結晶中を電子が通るという状況と類似している。電子バンドと同様に、フォトニック結晶中の電磁波の分散関係をフォトニックバンドと呼び、結晶中で電子バンドギャップに相当するエネルギーの電子が存在できないのと同じように、フォトニックバンドギャップに相当する周波数の電磁波はフォトニック結晶中に存在できない。このような性質を有するフォトニック結晶の制御技術の研究がなされている。 On the other hand, a photonic crystal is known as a crystal in which two kinds of substances having different dielectric constants (refractive indices) are artificially arranged alternately one-dimensionally, two-dimensionally or three-dimensionally. When an electromagnetic wave is incident on a photonic crystal, the wave travels through the material while feeling the periodicity of the dielectric constant, similar to the situation where electrons pass through a crystal in which atoms are periodically arranged. Similar to the electronic band, the dispersion relationship of electromagnetic waves in a photonic crystal is called a photonic band, and it corresponds to a photonic band gap just as an electron with an energy corresponding to the electronic band gap cannot exist in the crystal. Frequency electromagnetic waves cannot exist in the photonic crystal. Research on control technology of photonic crystals having such properties has been made.
　そして、フォトニック結晶を用いたテラヘルツ光発生も行われている。たとえば、その内部に非線形光学材料欠陥部を持つ１次元フォトニック結晶と、欠陥部を挟むミラーからなる共振器構造を備えるテラヘルツ光源が提案されている（特許文献２、参照）。この光源においては、１次元フォトニック結晶へフェムト秒パルスレーザ（多数の縦モード）の周波数の差分に相当するテラヘルツ光を発生し、１次元フォトニック結晶の共振波長に相当する波長をもつテラヘルツ光のみを取り出すものである。 And terahertz light generation using a photonic crystal is also performed. For example, a terahertz light source including a resonator structure including a one-dimensional photonic crystal having a nonlinear optical material defect portion therein and a mirror sandwiching the defect portion has been proposed (see Patent Document 2). In this light source, terahertz light corresponding to the frequency difference of a femtosecond pulse laser (multiple longitudinal modes) is generated on a one-dimensional photonic crystal, and terahertz light having a wavelength corresponding to the resonance wavelength of the one-dimensional photonic crystal. Only take out.
　また、第１及び第２のフォトニック結晶構造の間に非線形結晶からなる不純物構造を設けた光デバイスも提案されている（特許文献３、参照）。この光デバイスにおいては、非線形光学結晶の厚みや隣接するフォトニック結晶の表面状態を変更することによって、入射したフェムト秒パルスレーザの多数の縦モード周波数の差分に相当するテラヘルツ光のスペクトルや強度を調整する。 Also proposed is an optical device in which an impurity structure made of a nonlinear crystal is provided between the first and second photonic crystal structures (see Patent Document 3). In this optical device, by changing the thickness of the nonlinear optical crystal and the surface state of the adjacent photonic crystal, the spectrum and intensity of the terahertz light corresponding to the difference between the many longitudinal mode frequencies of the incident femtosecond pulse laser can be changed. adjust.
　さらに、放射されるテラヘルツ光のスペクトル成分が厚みにより変化する非線形光学結晶からなりかつ厚みが連続的に変化するウェッジ構造を有したテラヘルツ光発生素子も提案されている（特許文献４、参照）。これは、入射されるパルス光のフェムト秒パルスレーザ照射によりテラヘルツ光を放射するものであって、そのパルス光照射位置を変更することによって非線形光学結晶の厚さを可変させ、発生した広帯域のテラヘルツ光の波長を変更している。 Furthermore, a terahertz light generating element having a wedge structure in which the spectral component of the emitted terahertz light is made of a nonlinear optical crystal that varies with thickness and has a continuously varying thickness has been proposed (see Patent Document 4). This is to emit terahertz light by femtosecond pulse laser irradiation of incident pulsed light, and by changing the irradiation position of the pulsed light, the thickness of the nonlinear optical crystal is varied, and the generated broadband terahertz is generated. The wavelength of light is changed.
特開２００６－９１８０２JP 2006-91802 A 特開２００９－０８０４４８JP2009-080448 特開２００４－１０２１５９JP 2004-102159 A 特開２００５－０９９４５３JP 2005-099453 A
　しかしながら、特許文献１記載の先行技術では、導波路構造の形成が難しく高価になり、集光光学系を用いると光学系が複雑になる問題点がある。 However, in the prior art described in Patent Document 1, it is difficult and expensive to form a waveguide structure, and there is a problem that the optical system becomes complicated when a condensing optical system is used.
　また、特許文献２記載の先行技術では、欠陥部をもつ１次元フォトニック結晶は、フォトニックバンドギャップに相当する波長の光を選択的に取り出すことができるが、フォトニックバンドギャップはフォトニック結晶を構成する光学媒質の屈折率と厚さによって一義的に決まるため、非線形光学結晶を用いたテラヘルツ光の差周波発生の特徴である波長可変性を生かすことができない問題点がある。 In the prior art described in Patent Document 2, a one-dimensional photonic crystal having a defect portion can selectively extract light having a wavelength corresponding to the photonic band gap, but the photonic band gap is a photonic crystal. Therefore, there is a problem that wavelength variability, which is a feature of the difference frequency generation of terahertz light using a nonlinear optical crystal, cannot be utilized.
　また、特許文献３記載の先行技術では、非線形光学結晶の厚みや隣接するフォトニック結晶の表面状態を変更していることから、それぞれ独立した複数のデバイスを作製しており、デバイスの変更なしにテラヘルツ光のスペクトルや強度を調整することはできず、フェムト秒パルスレーザを用いる以上は、単色性の優れたテラヘルツ光を取り出すことができない問題点がある。 Further, in the prior art described in Patent Document 3, since the thickness of the nonlinear optical crystal and the surface state of the adjacent photonic crystal are changed, a plurality of independent devices are produced, and the device is not changed. The spectrum and intensity of terahertz light cannot be adjusted, and there is a problem that terahertz light with excellent monochromaticity cannot be extracted as long as a femtosecond pulse laser is used.
　また、特許文献４記載の先行技術でも、フェムト秒パルスレーザを用いる以上は、単色性の優れたテラヘルツ光を取り出すことができず、波長選択を高めるための１次元フォトニック結晶など共振器構造を利用することが難しい問題点がある。 In the prior art described in Patent Document 4, as long as a femtosecond pulse laser is used, terahertz light having excellent monochromaticity cannot be extracted, and a resonator structure such as a one-dimensional photonic crystal for enhancing wavelength selection is used. There are problems that are difficult to use.
　本発明は、このような問題に対処することを課題の一例とするものである。すなわち、小型かつ高強度の可変周波数型のテラヘルツ光発生装置及び方法を提供することが本発明の目的の一例である。 The present invention is an example of a problem to deal with such a problem. That is, it is an example of an object of the present invention to provide a small and high intensity variable frequency terahertz light generating apparatus and method.
　本発明によるテラヘルツ光発生装置は、レーザ光の入射によりテラヘルツ帯域の電磁波を放射するテラヘルツ光発生装置であって、高屈折率及び低屈折率の誘電体層が交互に積層された１次元フォトニック結晶の周期方向において非線形光学結晶からなる欠陥層を介在させた増幅用光学素子と、前記欠陥層を通り前記１次元フォトニック結晶の周期方向に垂直な方向に回転軸を有しかつ前記増幅用光学素子を前記回転軸まわりに回転せしめる回転機構と、を含み、前記１次元フォトニック結晶の周期方向に、少なくとも２つの互いに近傍の周波数を有するレーザ光を入射させ、前記回転機構により入射角度を相対的に変化させることによって、放射される前記電磁波の周波数を変化せしめる制御装置を有することを特徴とする。 A terahertz light generating device according to the present invention is a terahertz light generating device that emits terahertz band electromagnetic waves upon incidence of laser light, and is a one-dimensional photonic in which dielectric layers of high refractive index and low refractive index are alternately stacked. An amplification optical element having a defect layer made of a non-linear optical crystal in the periodic direction of the crystal, a rotation axis passing through the defect layer and perpendicular to the periodic direction of the one-dimensional photonic crystal, and the amplification A rotation mechanism that rotates an optical element around the rotation axis, and at least two laser beams having frequencies close to each other are incident in a periodic direction of the one-dimensional photonic crystal, and an incident angle is adjusted by the rotation mechanism. It has a control device which changes the frequency of the electromagnetic wave radiated by changing it relatively.
　本発明によるテラヘルツ光発生装置においては、前記レーザ光とテラヘルツ光が同一光軸上に配置するコリニア位相整合によってテラヘルツ光を発生させることとすることができる。 In the terahertz light generating device according to the present invention, the terahertz light can be generated by collinear phase matching in which the laser light and the terahertz light are arranged on the same optical axis.
　本発明によるテラヘルツ光発生装置においては、前記レーザ光として、波長の異なる２本のレーザ光をポンプ光とする光源を含み、前記２本のポンプ光の周波数の差に相当する周波数を有するテラヘルツ光を発生することとすることができる。 In the terahertz light generation device according to the present invention, the laser light includes a light source that uses two laser lights having different wavelengths as pump light, and has a frequency corresponding to a difference in frequency between the two pump lights. Can be generated.
　本発明によるテラヘルツ光発生装置においては、前記制御装置は２本のポンプ光のうち少なくとも１本の周波数を変更する光源波長粗調部を含み、周波数変更されたポンプ光によって、テラヘルツ光の周波数を変更することとすることができる。 In the terahertz light generation device according to the present invention, the control device includes a light source wavelength rough adjustment unit that changes the frequency of at least one of the two pump lights, and the frequency of the terahertz light is adjusted by the pump light having the frequency changed. It can be changed.
　本発明によるテラヘルツ光発生装置においては、前記制御装置は、前記周波数変更されたポンプ光の周波数に応じて、前記回転機構を駆動し前記増幅用光学素子を回転せしめる回転制御部を含むこととすることができる。 In the terahertz light generation device according to the present invention, the control device includes a rotation control unit that drives the rotation mechanism and rotates the amplification optical element according to the frequency of the pump light whose frequency has been changed. be able to.
　本発明によるテラヘルツ光発生装置においては、発生するテラヘルツ光の強度を検出するセンサを含み、前記回転制御部は発生するテラヘルツ光の強度が最大になるように前記レーザ光の入射角度を微調整することとすることができる。 The terahertz light generator according to the present invention includes a sensor that detects the intensity of the generated terahertz light, and the rotation control unit finely adjusts the incident angle of the laser light so that the intensity of the generated terahertz light is maximized. Can be.
　本発明によるテラヘルツ光発生装置においては、前記非線形光学結晶は、ＧａＰ、ＺｎＴｅ、ＧａＳｅ、またはＤＡＳＴ（4-dimethylamino-N-methyl-4-stilbazolium tosylate）であることとすることができる。 In the terahertz light generator according to the present invention, the nonlinear optical crystal can be GaP, ZnTe, GaSe, or DAST (4-dimethylamino-N-methyl-4-stilbazolium-tosylate).
　本発明によるテラヘルツ光発生装置においては、前記１次元フォトニック結晶の高屈折率及び低屈折率の誘電体層は溶融石英ガラス及びポリエチレンであることとすることができる。 In the terahertz light generator according to the present invention, the high refractive index and low refractive index dielectric layers of the one-dimensional photonic crystal may be fused silica glass and polyethylene.
　本発明によるテラヘルツ光発生装置においては、前記レーザ光の周波数差は０．１～１００ＴＨｚのテラヘルツ周波数帯域にあることとすることができる。 In the terahertz light generator according to the present invention, the frequency difference of the laser light may be in a terahertz frequency band of 0.1 to 100 THz.
　本発明のテラヘルツ光発生方法は、レーザ光の入射によりテラヘルツ帯域の電磁波を放射するテラヘルツ光発生方法であって、高屈折率及び低屈折率の誘電体層が交互に積層された１次元フォトニック結晶の周期方向において非線形光学結晶からなる欠陥層を介在させた増幅用光学素子を用意する工程と、前記１次元フォトニック結晶の周期方向に、少なくとも２つの互いに近傍の周波数を有するレーザ光を同一光軸上に入射させる工程と、前記レーザ光のうち少なくとも１本の周波数を変更する工程と、前記欠陥層を通り前記１次元フォトニック結晶の周期方向に垂直な方向に伸長する回転軸まわりに前記増幅用光学素子を回転せしめ前記レーザ光の入射角度を相対的に変化させることによって、放射される前記電磁波の周波数を変化せしめる粗調工程と、を含むことを特徴とする。 The terahertz light generation method of the present invention is a terahertz light generation method that emits terahertz band electromagnetic waves upon incidence of laser light, and is a one-dimensional photonic in which dielectric layers of high refractive index and low refractive index are alternately stacked. The step of preparing an amplifying optical element having a defect layer made of a nonlinear optical crystal in the periodic direction of the crystal is the same as the laser light having at least two frequencies close to each other in the periodic direction of the one-dimensional photonic crystal. A step of making it incident on the optical axis, a step of changing the frequency of at least one of the laser beams, and a rotation axis extending through the defect layer in a direction perpendicular to the periodic direction of the one-dimensional photonic crystal. By rotating the amplification optical element and relatively changing the incident angle of the laser beam, the frequency of the emitted electromagnetic wave is changed. Characterized in that it comprises a Mel coarse step.
　本発明によるテラヘルツ光発生装置によれば、非線形光学結晶を用いたテラヘルツ光の差周波発生の特徴である波長可変性を生かすことができる小型かつ高強度のテラヘルツ光源が提供できる。このテラヘルツ光発生装置においては、高屈折率及び低屈折率の誘電体層が交互に積層された１次元フォトニック結晶の周期方向の中間に配置された非線形光学結晶欠陥層と当該欠陥層を挟むミラーからなる共振器構造を備える回転自在な増幅用光学素子するので、当該増幅用光学素子に入射される異なる波長を持つ２本のポンプ光の周波数の差分に相当するテラヘルツ光が発生（差周波発生）したとき、当該増幅用光学素子の回転により、１次元フォトニック結晶の共振波長に相当する波長をもつテラヘルツ光のみを精度よく取り出すことができ、所望の波長をもつテラヘルツ光を増幅することができる。これにより、出力テラヘルツ光の品質を向上できる。 The terahertz light generator according to the present invention can provide a small and high-intensity terahertz light source that can take advantage of the wavelength variability that is characteristic of the difference frequency generation of terahertz light using a nonlinear optical crystal. In this terahertz light generation device, a non-linear optical crystal defect layer disposed in the middle of a periodic direction of a one-dimensional photonic crystal in which dielectric layers having a high refractive index and a low refractive index are alternately stacked, and the defect layer are sandwiched Since the amplifying optical element having a resonator structure including a mirror is rotatable, terahertz light corresponding to the difference in frequency between two pump lights having different wavelengths incident on the amplifying optical element is generated (difference frequency). The terahertz light having a wavelength corresponding to the resonance wavelength of the one-dimensional photonic crystal can be extracted with high accuracy by the rotation of the amplification optical element, and the terahertz light having a desired wavelength is amplified. Can do. Thereby, the quality of output terahertz light can be improved.
本発明の実施形態にかかるテラヘルツ光発生装置の模式図である。It is a mimetic diagram of a terahertz light generator concerning an embodiment of the present invention. 本発明の実施形態にかかるテラヘルツ光発生装置の増幅用光学素子の概略部分断面図である。1 is a schematic partial cross-sectional view of an amplification optical element of a terahertz light generator according to an embodiment of the present invention. 本発明の実施形態にかかるテラヘルツ光発生装置によるテラヘルツ光発生方法の一例を示すフローチャートである。It is a flowchart which shows an example of the terahertz light generation method by the terahertz light generator concerning embodiment of this invention. 本発明の実施形態にかかるテラヘルツ光発生装置の増幅用光学素子の断面図である。It is sectional drawing of the optical element for amplification of the terahertz light generator concerning embodiment of this invention. 本発明の他の実施形態にかかるテラヘルツ光発生装置において入射角度を変化させた場合の、テラヘルツ光周波数に対するテラヘルツ光強度の変化を示すグラフである。It is a graph which shows the change of the terahertz light intensity with respect to the terahertz light frequency at the time of changing an incident angle in the terahertz light generator concerning other embodiment of this invention.
　１１　テラヘルツ光発生装置
　１２，４２　増幅用光学素子
　１３　回転機構
　１４　欠陥層
　２１　可変波長のレーザ光源
　２２　固定波長のレーザ光源
　２３，２４　ハーフミラー
　３１　制御装置
　３２　センサ
　４４　非線形光学結晶
　３３　光学フィルタ
　１３１　回転ステージ
　Ｈ　高屈折率の誘電体層
　Ｌ　低屈折率の誘電体層
　Ｍ１，Ｍ２　多層
　θ　入射角度
　O　回転軸 DESCRIPTION OF SYMBOLS 11 Terahertz light generator 12, 42 Optical element for amplification 13 Rotating mechanism 14 Defect layer 21 Laser light source of variable wavelength 22 Laser light source of fixed wavelength 23, 24 Half mirror 31 Controller 32 Sensor 44 Nonlinear optical crystal 33 Optical filter 131 Rotating stage H Dielectric layer with high refractive index L Dielectric layer with low refractive index M1, M2 Multilayer θ Incident angle O Rotation axis
　本発明によるテラヘルツ光発生装置の実施形態について添付の図面を参照しつつ説明する。なお、実施形態は例示に過ぎずこれらに本発明は制限されないことはいうまでもない。 Embodiments of a terahertz light generator according to the present invention will be described with reference to the accompanying drawings. Needless to say, the embodiments are merely examples, and the present invention is not limited thereto.
　＜テラヘルツ光発生装置の構成＞
　図１は本発明による実施形態のテラヘルツ光発生装置の模式図である。 <Configuration of terahertz light generator>
FIG. 1 is a schematic diagram of a terahertz light generator according to an embodiment of the present invention.
　本実施形態のテラヘルツ光発生装置１１は増幅用光学素子１２と、増幅用光学素子を保持する回転機構１３とを含んでいる。図２は、増幅用光学素子１２としての１次元フォトニック結晶の概略断面図である。 The terahertz light generation device 11 of the present embodiment includes an amplification optical element 12 and a rotation mechanism 13 that holds the amplification optical element. FIG. 2 is a schematic cross-sectional view of a one-dimensional photonic crystal as the amplification optical element 12.
　図２に示すように、増幅用光学素子１２の１次元フォトニック結晶は、高屈折率の誘電体層Ｈ及び低屈折率の誘電体層Ｌの対が周期的に交互に複数積層された多層Ｍ１，Ｍ２の構造を有し、それらの間（中央部）に欠陥層１４として所定膜厚の非線形光学結晶層を設けて構成されている。１次元フォトニック結晶の高屈折率及び低屈折率の誘電体層Ｈ，Ｌ（高屈折率層及び低屈折率層）は、たとえば溶融石英ガラス及びポリエチレンである。欠陥層１４の非線形光学結晶は高い２次非線形光学係数の、たとえば、無機材料のＧａＰ、ＺｎＴｅ、ＧａＳｅ、または、有機材料のＤＡＳＴ（4-dimethylamino-N-methyl-4-stilbazolium tosylate）である。このように、増幅用光学素子１２は、高屈折率（ｎＨ）及び低屈折率（ｎＬ＜ｎＨ）の誘電体層（それぞれ光学膜厚：ｎＨ・ｄＨ及びｎＬ・ｄＬを有する。ただし、ｄＨ及びｄＬはそれぞれの膜厚である）が交互に積層された１次元フォトニック結晶の膜厚方向（周期方向）において非線形光学結晶からなる欠陥層１４を介在させて構成される。増幅用光学素子１２では、多層Ｍ１，Ｍ２が高反射率の誘電体多層膜ミラーに対応して共振器を構成し、共振器中に非線形光学結晶が設けられている。 As shown in FIG. 2, the one-dimensional photonic crystal of the amplifying optical element 12 is a multilayer in which a plurality of pairs of high refractive index dielectric layers H and low refractive index dielectric layers L are alternately stacked. It has a structure of M1 and M2, and a non-linear optical crystal layer having a predetermined film thickness is provided as a defect layer 14 between them (central part). The high refractive index and low refractive index dielectric layers H and L (high refractive index layer and low refractive index layer) of the one-dimensional photonic crystal are, for example, fused silica glass and polyethylene. The nonlinear optical crystal of the defect layer 14 has a high second-order nonlinear optical coefficient, such as GaP, ZnTe, GaSe as an inorganic material, or DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) as an organic material. As described above, the amplifying optical element 12 includes dielectric layers having high refractive index (n H ) and low refractive index (n L <n H ) (optical film thicknesses: n H · d H and n L · d L, respectively). (Where d H and d L are the respective film thicknesses), and the defect layer 14 made of a nonlinear optical crystal is interposed in the film thickness direction (period direction) of the one-dimensional photonic crystal laminated alternately. Composed. In the amplifying optical element 12, the multilayers M1 and M2 constitute a resonator corresponding to a dielectric multilayer mirror having a high reflectance, and a nonlinear optical crystal is provided in the resonator.
　図２に示すフォトニック結晶の多層Ｍ１側から多層Ｍ２へ所定周波数帯域のレーザ光を入射した場合、その透過光スペクトルを観察すると、欠陥層がある場合は鋭い透過ピークが現れる。フォトニック結晶に欠陥層がある場合、フォトニックバンドギャップ中に欠陥準位ができ、欠陥準位に相当する波長の光が透過することとなる。欠陥層に共鳴する光を入射すると１次元フォトニック結晶中で多重反射が生じ、光電場は欠陥層のまわりに局在化する。一方、欠陥層を含まない場合は広い範囲で透過率が低い領域が存在する（フォトニックバンドギャップ）が、透過ピークは現れない。欠陥準位に対応した波長の光を入射させた場合、この欠陥モードと結合することで透過が許されるようになる。 When a laser beam of a predetermined frequency band is incident on the multilayer M2 from the multilayer M1 side of the photonic crystal shown in FIG. 2, when the transmitted light spectrum is observed, a sharp transmission peak appears when there is a defect layer. When the photonic crystal has a defect layer, a defect level is formed in the photonic band gap, and light having a wavelength corresponding to the defect level is transmitted. When light that resonates with the defect layer is incident, multiple reflection occurs in the one-dimensional photonic crystal, and the photoelectric field is localized around the defect layer. On the other hand, when a defect layer is not included, a region having a low transmittance exists in a wide range (photonic band gap), but a transmission peak does not appear. When light having a wavelength corresponding to the defect level is incident, coupling with this defect mode allows transmission.
　欠陥準位に対応した波長の光を入射した場合、欠陥層における光電場の振幅は入射光電場の振幅と較べて大きくなる。欠陥層における電場振幅の増幅度Ｇは、欠陥層の両側がそれぞれＮ周期の周期的な多層Ｍ１，Ｍ２であるとするとＧ＝（ｎＨ／ｎＬ）Ｎとなる。ここで（ｎＨ／ｎＬ）は高屈折率層及び低屈折率層Ｈ，Ｌの屈折率比である。よって、欠陥層が非線形光学結晶であるので、この増幅された光強度に起因して非線形光学効果（差周波発生のテラヘルツ光）が大きく増幅される。 When light having a wavelength corresponding to the defect level is incident, the amplitude of the photoelectric field in the defect layer is larger than the amplitude of the incident photoelectric field. The amplification degree G of the electric field amplitude in the defect layer is G = (n H / n L ) N , assuming that both sides of the defect layer are periodic multilayers M1 and M2 each having N periods. Here, (n H / n L ) is a refractive index ratio between the high refractive index layer and the low refractive index layers H and L. Therefore, since the defect layer is a nonlinear optical crystal, the nonlinear optical effect (terahertz light generated by difference frequency) is greatly amplified due to the amplified light intensity.
　図１に示すように、テラヘルツ光発生装置１１の回転機構１３は、欠陥層１４を通り１次元フォトニック結晶Ｍ１，Ｍ２の周期方向に垂直な方向に伸長する回転軸Oを有しかつ増幅用光学素子１２を回転軸Oまわりに回転せしめる回転ステージ１３１を含んでいる。回転機構１３は、電気的に制御できる回転ステージ１３１を回転又は回動せしめるモータやその駆動機構（図示せず）を含む。 As shown in FIG. 1, the rotation mechanism 13 of the terahertz light generator 11 has a rotation axis O extending through a defect layer 14 in a direction perpendicular to the periodic direction of the one-dimensional photonic crystals M1 and M2, and for amplification. A rotation stage 131 for rotating the optical element 12 around the rotation axis O is included. The rotation mechanism 13 includes a motor that rotates or rotates an electrically controllable rotation stage 131 and a drive mechanism (not shown).
　図１に示すテラヘルツ光発生装置１１は、レーザ光として、波長の異なる２本のレーザ光をポンプ光とする２つの可変波長のレーザ光源２１及び固定波長のレーザ光源２２を含む。これら励起レーザ光源２１，２２はＤＦＢやＤＢＲなどの単一モードのレーザである。一方のレーザ光源２１の射出ポンプ光の光軸を、１次元フォトニック結晶Ｍ１，Ｍ２の回転軸Oを通過するように、増幅用光学素子１２とレーザ光源２１を配置し、他方のレーザ光源２２からの射出ポンプ光を、光軸上に配置されたハーフミラー２３で反射させて、両ポンプ光を同一光軸上で増幅用光学素子１２へ入射させる。レーザ光源２１，２２の２本のポンプ光の周波数ω１，ω２の差に相当する周波数（ω３＝ω１－ω２）を有するテラヘルツ光を発生する。すなわち、テラヘルツ光発生装置１１は、ポンプ光とテラヘルツ光が同一光軸上に配置するコリニア位相整合によってテラヘルツ光を発生させる。 The terahertz light generator 11 shown in FIG. 1 includes two variable wavelength laser light sources 21 and a fixed wavelength laser light source 22 that use two laser lights having different wavelengths as pump light. These excitation laser light sources 21 and 22 are single mode lasers such as DFB and DBR. The amplification optical element 12 and the laser light source 21 are arranged so that the optical axis of the injection pump light of one laser light source 21 passes through the rotation axis O of the one-dimensional photonic crystals M1 and M2, and the other laser light source 22 is disposed. The pump light emitted from the light beam is reflected by the half mirror 23 arranged on the optical axis, and both pump lights are incident on the amplification optical element 12 on the same optical axis. Terahertz light having a frequency (ω3 = ω1−ω2) corresponding to the difference between the frequencies ω1 and ω2 of the two pump lights of the laser light sources 21 and 22 is generated. That is, the terahertz light generation device 11 generates terahertz light by collinear phase matching in which pump light and terahertz light are arranged on the same optical axis.
　このように、図１に示すテラヘルツ光発生装置１１においては、１次元フォトニック結晶の周期方向に、少なくとも２つの互いに近傍の周波数を有するポンプ光を入射させ、回転機構により入射角度θを相対的に変化させることによって、放射されるテラヘルツ光の周波数を変化せしめる。すなわち、図１に示すテラヘルツ光発生装置１１は、可変波長のレーザ光源２１に接続された制御装置３１を含み、制御装置３１はそのポンプ光の周波数を変更する光源波長粗調部として機能する。制御装置３１により周波数変更されたポンプ光（ω１±α）によって、出力のテラヘルツ光の周波数を微妙に変更する。 As described above, in the terahertz light generating device 11 shown in FIG. 1, at least two pump lights having frequencies close to each other are incident in the periodic direction of the one-dimensional photonic crystal, and the incident angle θ is relatively set by the rotation mechanism. By changing to, the frequency of the terahertz light emitted is changed. That is, the terahertz light generation device 11 shown in FIG. 1 includes a control device 31 connected to a variable wavelength laser light source 21, and the control device 31 functions as a light source wavelength rough adjustment unit that changes the frequency of the pump light. The pump light (ω1 ± α) whose frequency is changed by the control device 31 slightly changes the frequency of the output terahertz light.
　図１に示すテラヘルツ光発生装置１１の制御装置３１は、さらに回転機構１３に接続され、周波数変更されたポンプ光の周波数（ω１±α）に応じて回転機構１３を制御、駆動し１次元フォトニック結晶Ｍ１，Ｍ２を回転せしめる回転制御部（光源波長微調部）として機能する。 The control device 31 of the terahertz light generation device 11 shown in FIG. 1 is further connected to the rotation mechanism 13, and controls and drives the rotation mechanism 13 in accordance with the frequency (ω1 ± α) of the pump light whose frequency has been changed. It functions as a rotation control unit (light source wavelength fine tuning unit) that rotates the nick crystals M1 and M2.
　また、図１に示すテラヘルツ光発生装置１１は、制御装置３１に接続されて、発生するテラヘルツ光の強度を検出するセンサ３２を含む。センサ３２は増幅用光学素子１２のポンプ光反対側のポンプ光およびテラヘルツ光の光軸からテラヘルツ光を分岐するハーフミラー２４の下流の光軸へ配置される。回転制御部としての制御装置３１は、さらに、センサ３２で検出されたテラヘルツ光の強度が最大になるようにポンプ光（ω１，ω２）の相対的入射角度θを回転機構１３により微調整する。 The terahertz light generation device 11 shown in FIG. 1 includes a sensor 32 that is connected to the control device 31 and detects the intensity of the generated terahertz light. The sensor 32 is disposed on the optical axis downstream of the half mirror 24 that branches the terahertz light from the optical axis of the pump light and terahertz light opposite to the pump light of the amplification optical element 12. The control device 31 as the rotation control unit further finely adjusts the relative incident angle θ of the pump light (ω1, ω2) by the rotation mechanism 13 so that the intensity of the terahertz light detected by the sensor 32 is maximized.
　＜テラヘルツ光発生装置の具体的な構成例＞
　テラヘルツ光発生装置の増幅用光学素子の非線形光学結晶として１０ｍｍ角厚さ１ｍｍのテルル化亜鉛（ＺｎＴｅ）の小片を用いる。ＺｎＴｅ片の両面に屈折率の異なる層を積層した１次元フォトニック結晶を作製しＺｎＴｅ片を欠陥層として機能させる。高屈折率層には溶融石英ガラスを、低屈折率層にはポリエチレンを用いる。厚さはそれぞれ１９ミクロンおよび２７ミクロンとする。このとき、増幅用光学素子に対してポンプ光を垂直入射させると増幅されるテラヘルツ光の周波数は２ＴＨｚになる。 <Specific configuration example of terahertz light generator>
A small piece of zinc telluride (ZnTe) having a 10 mm square and a thickness of 1 mm is used as the nonlinear optical crystal of the amplification optical element of the terahertz light generator. A one-dimensional photonic crystal in which layers having different refractive indexes are laminated on both sides of a ZnTe piece is produced, and the ZnTe piece is caused to function as a defect layer. Fused silica glass is used for the high refractive index layer, and polyethylene is used for the low refractive index layer. The thickness is 19 microns and 27 microns, respectively. At this time, the frequency of the terahertz light to be amplified is 2 THz when the pump light is vertically incident on the amplification optical element.
　次に、防振台上に回転ステージ、増幅用光学素子、光源等を設置してテラヘルツ光発生装置を組み立てる。 Next, a terahertz light generator is assembled by installing a rotating stage, an amplification optical element, a light source, etc. on a vibration isolator.
　増幅用光学素子をステッピングモータ駆動自動回転ステージ、たとえばシグマ光機製SGSP-40YAWなどを介して防振台上に取り付ける。光源は、たとえば固定波長レーザとしてFrankfurt Laser社（ドイツ）の高出力ＤＦＢレーザダイオード（シングルモード固定波長、出力１００ｍＷ以上）と、Sacher Lasertechnik社（ドイツ）の高出力リトロー型外部共振器波長可変レーザTiger（可変波長域７５０ｎｍ～１０７０ｎｍ、出力１００ｍＷ以上）を用いる。これら２つの光源から出射する２本のポンプ光を適宜光学ミラー等を用いて同軸上に配置し増幅用光学素子に導く。 The optical element for amplification is mounted on a vibration isolation table via a stepping motor driven automatic rotation stage such as SGSP-40YAW manufactured by Sigma Kogyo. The light source includes, for example, a high-power DFB laser diode (single-mode fixed wavelength, output of 100 mW or more) from Frankfurt Laser (Germany) as a fixed wavelength laser, and a high-power Littrow external cavity tunable laser Tiger from Sacher Lasertechnik (Germany). (Variable wavelength range 750 nm to 1070 nm, output 100 mW or more). Two pump lights emitted from these two light sources are arranged on the same axis using an optical mirror as appropriate, and guided to the amplification optical element.
　ここで、テラヘルツ光発生装置によるテラヘルツ光発生方法を、図３に示すフローチャートを参照して説明する。 Here, a terahertz light generation method using the terahertz light generation apparatus will be described with reference to a flowchart shown in FIG.
　まず、用意した増幅用光学素子の１次元フォトニック結晶の周期方向に２本のポンプ光をコリニアに入射させるように光学系を調整する。出力波長選択では、所望の周波数をもつテラヘルツ光が得られるように、波長可変レーザの出力波長を設定し（波長可変レーザの波長設定：Ｓ１）、粗調整する。そして、自動回転ステージを所定の角度に回転させ増幅用光学素子へ入射するポンプ光の入射角度を制御する（素子入射角度調整：Ｓ２）。たとえば、２．２４ＴＨｚのテラヘルツ光を発生させたい場合には、固定波長レーザの出力波長が８００．０ｎｍであるとすると、波長可変レーザの出力波長を８０４．８ｎｍに設定し、入射角度が４５度になるように、自動回転ステージを調整する。 First, the optical system is adjusted so that two pump lights are incident collinearly in the periodic direction of the one-dimensional photonic crystal of the prepared amplification optical element. In the output wavelength selection, the output wavelength of the wavelength tunable laser is set (wavelength setting of the wavelength tunable laser: S1) so that terahertz light having a desired frequency is obtained, and coarse adjustment is performed. Then, the incident angle of the pump light incident on the amplification optical element is controlled by rotating the automatic rotation stage to a predetermined angle (element incident angle adjustment: S2). For example, when it is desired to generate terahertz light of 2.24 THz, if the output wavelength of the fixed wavelength laser is 800.0 nm, the output wavelength of the wavelength tunable laser is set to 804.8 nm and the incident angle is 45 degrees. Adjust the automatic rotation stage so that
　固定波長レーザと波長可変レーザをオン状態とする（レーザON：Ｓ３）。 The fixed wavelength laser and the wavelength tunable laser are turned on (laser ON: S3).
　発生したテラヘルツ光は１次元フォトニック結晶構造によって増幅され、ポンプ光と同軸上、ポンプ光と逆側へ取り出される。テラヘルツ光の強度を別途用意した受光光学系、たとえばシリコンボロメータなどによって検出し（テラヘルツ光出力測定：Ｓ４）、テラヘルツ光強度が最大か否か判断し（テラヘルツ光出力最大?：Ｓ５）、テラヘルツ光強度が最大になるように、自動回転ステージを駆動してポンプ光入射角を粗調整および微調整を行う。 The generated terahertz light is amplified by a one-dimensional photonic crystal structure, and is extracted coaxially with the pump light and opposite to the pump light. The intensity of the terahertz light is detected by a light receiving optical system such as a silicon bolometer (terahertz light output measurement: S4), and it is determined whether or not the terahertz light intensity is maximum (maximum terahertz light output: S5). In order to maximize the intensity, the automatic rotation stage is driven to roughly adjust and finely adjust the incident angle of the pump light.
　このときテラヘルツ光の強度をさらに増幅するために特開２００６－９１８０２に記載されているようにポンプ光を光学レンズで集光して増幅用光学素子に入射させるなどしても良い。 At this time, in order to further amplify the intensity of the terahertz light, as described in JP-A-2006-91802, the pump light may be condensed by an optical lens and made incident on the amplification optical element.
　＜テラヘルツ光発生装置の具体的な１次元フォトニック結晶の構成例＞
　増幅用光学素子において増幅したいテラヘルツ光の周波数に対する増幅用光学素子の構成および入射角度制御の例を挙げる。ここで１次元フォトニック結晶の高屈折率層は溶融石英ガラス（屈折率１．９６）で、低屈折率層はポリエチレン（屈折率１．３７）とした。また、テラヘルツ光発生用の非線形光学結晶としてテルル化亜鉛（ＺｎＴｅ）を用いた。 <Specific configuration example of one-dimensional photonic crystal of terahertz light generator>
An example of the configuration of the amplification optical element and the incident angle control with respect to the frequency of the terahertz light to be amplified in the amplification optical element is given. Here, the high refractive index layer of the one-dimensional photonic crystal was fused silica glass (refractive index 1.96), and the low refractive index layer was polyethylene (refractive index 1.37). Further, zinc telluride (ZnTe) was used as a nonlinear optical crystal for generating terahertz light.
　図４に、テラヘルツ光発生装置の増幅用光学素子４２の断面図を示す。ポンプ光の入射側から低屈折率層／高屈折率層の順に５組積層し、次に欠陥層として非線形光学結晶を用い、次に高屈折率層／低屈折率層の順に５組積層することで増幅用光学素子を構成した。このとき、高屈折率層である溶融石英ガラスの厚さは１９．１ミクロン、低屈折率層であるポリエチレンの厚さは２７．４ミクロン、非線形光学結晶であるテルル化亜鉛（ＺｎＴｅ）の厚さは１ｍｍとした。図中、Ｈは溶融石英ガラス、Ｌはポリエチレン、４４はＺｎＴｅである。 FIG. 4 shows a cross-sectional view of the amplification optical element 42 of the terahertz light generator. Five pairs of low refractive index layer / high refractive index layer are stacked in this order from the incident side of the pump light, then a nonlinear optical crystal is used as a defect layer, and then five sets of high refractive index layer / low refractive index layer are stacked in this order. Thus, an amplification optical element was configured. At this time, the thickness of the fused silica glass that is the high refractive index layer is 19.1 microns, the thickness of the polyethylene that is the low refractive index layer is 27.4 microns, and the thickness of zinc telluride (ZnTe) that is a nonlinear optical crystal. The thickness was 1 mm. In the figure, H is fused silica glass, L is polyethylene, and 44 is ZnTe.
　図５に、入射角度を０度、３０度、４５度に変化させた場合の、テラヘルツ光周波数に対するテラヘルツ光強度の変化をグラフに示す。テラヘルツ光強度はテラヘルツ光周波数に対して周期的に増幅されるが、入射角度に対して増幅率の高い周波数がある。入射角度が０度の場合は、２．０６ＴＨｚのテラヘルツ光を効率よく増幅する。また、入射角度が３０度の場合は２．１５ＴＨｚのテラヘルツ光に対して、入射角度が４５度の場合は２．２４ＴＨｚのテラヘルツ光に対して増幅効率が良好である。このように、固定波長レーザの出力波長が８００．０ｎｍであるとき、波長可変レーザの出力波長を８０４．８ｎｍに設定し、入射角度が４５度になるように、自動回転ステージを調整することによって、２．２４ＴＨｚのテラヘルツ光を発生させることができる。 FIG. 5 is a graph showing changes in the terahertz light intensity with respect to the terahertz light frequency when the incident angle is changed to 0 degrees, 30 degrees, and 45 degrees. Although the terahertz light intensity is periodically amplified with respect to the terahertz light frequency, there is a frequency having a high amplification factor with respect to the incident angle. When the incident angle is 0 degree, 2.06 THz terahertz light is efficiently amplified. In addition, the amplification efficiency is good for 2.15 THz terahertz light when the incident angle is 30 degrees, and 2.24 THz terahertz light when the incident angle is 45 degrees. Thus, when the output wavelength of the fixed wavelength laser is 800.0 nm, the output wavelength of the tunable laser is set to 804.8 nm, and the automatic rotation stage is adjusted so that the incident angle is 45 degrees. , 2.24 THz terahertz light can be generated.
　＜他の構成例１＞
　テラヘルツ光発生装置において、非線形光学結晶にガリウム燐（ＧａＰ）を用い、光源波長が９９０ｎｍ付近の固定波長レーザと波長可変レーザを用いる以外、上記構成例と同一とする。 <Other configuration example 1>
The terahertz light generator is the same as the above configuration example except that gallium phosphide (GaP) is used for the nonlinear optical crystal and a fixed wavelength laser and a wavelength tunable laser having a light source wavelength of about 990 nm are used.
　＜他の構成例２＞
　テラヘルツ光発生装置において、非線形光学結晶に、有機非線形光学結晶の4-dimethylamino-N-methyl-4-stilbazolium tosylate（ＤＡＳＴ）を用い、光源波長が７８０～８００ｎｍあるいは１０６４ｎｍ付近の固定波長レーザと波長可変レーザを用いる以外、上記構成例と同一とする。有機非線形光学結晶は、一般に高い非線形光学係数を有するとともに、光波帯とテラヘルツ波帯での屈折率差が小さいことから、差周波発生による高効率かつ広帯域なテラヘルツ光発生が期待される材料である。特に、イオン塩結晶ＤＡＳＴはその大きな非線形光学係数（ｄ１１＝２５０ｐｍ／Ｖ）とともに、コリニアな位相整合が０．８～１．６μｍ付近で得られる特性を持つ。さらに、テラヘルツ光偏光方向をＤＡＳＴ結晶のａ軸方向にほぼ一致させることでコリニア位相整合を満たすさらに良好な差周波発生を実現することができる。 <Other configuration example 2>
In the terahertz light generator, the organic nonlinear optical crystal 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) is used as the nonlinear optical crystal, and the wavelength of the light source is variable from 780 to 800 nm or 1064 nm. The above configuration example is the same except that a laser is used. Organic nonlinear optical crystals generally have high nonlinear optical coefficients and have a small difference in refractive index between the light wave band and the terahertz wave band. Therefore, organic nonlinear optical crystals are materials that are expected to generate high-efficiency and broadband terahertz light due to difference frequency generation. . In particular, the ionic salt crystal DAST has a characteristic that a collinear phase matching is obtained in the vicinity of 0.8 to 1.6 μm, together with its large nonlinear optical coefficient (d 11 = 250 pm / V). Furthermore, by making the polarization direction of the terahertz light substantially coincide with the a-axis direction of the DAST crystal, it is possible to realize better difference frequency generation that satisfies the collinear phase matching.
　＜他の構成例３＞
　上記のいずれの構成例においても、図１に示すテラヘルツ光発生装置１１において、増幅用光学素子１２と下流のハーフミラー２４の間に光学フィルタ３３を配置して、ポンプ光を遮断して、テラヘルツ光のみを透過する構成とすることもできる。 <Other configuration example 3>
In any of the above configuration examples, in the terahertz light generation device 11 shown in FIG. 1, the optical filter 33 is disposed between the amplification optical element 12 and the downstream half mirror 24 to block the pump light, and the terahertz light is generated. It can also be set as the structure which permeate | transmits only light.

Claims (10)

  1. 　レーザ光の入射によりテラヘルツ帯域の電磁波を放射するテラヘルツ光発生装置であって、
    　高屈折率及び低屈折率の誘電体層が交互に積層された１次元フォトニック結晶の周期方向において非線形光学結晶からなる欠陥層を介在させた増幅用光学素子と、
    　前記欠陥層を通り前記１次元フォトニック結晶の周期方向に垂直な方向に回転軸を有しかつ前記増幅用光学素子を前記回転軸まわりに回転せしめる回転機構と、を含み、
    　前記１次元フォトニック結晶の周期方向に、少なくとも２つの互いに近傍の周波数を有するレーザ光を入射させ、前記回転機構により入射角度を相対的に変化させることによって、放射される前記電磁波の周波数を変化せしめる制御装置を有することを特徴とするテラヘルツ光発生装置。     A terahertz light generator that emits electromagnetic waves in the terahertz band by the incidence of laser light,
    An amplification optical element having a defect layer made of a nonlinear optical crystal interposed in a periodic direction of a one-dimensional photonic crystal in which dielectric layers of high refractive index and low refractive index are alternately laminated;
    A rotation mechanism having a rotation axis in a direction perpendicular to the periodic direction of the one-dimensional photonic crystal through the defect layer and rotating the amplification optical element around the rotation axis,
    The frequency of the radiated electromagnetic wave is changed by causing at least two laser beams having frequencies close to each other to enter the periodic direction of the one-dimensional photonic crystal and relatively changing the incident angle by the rotation mechanism. A terahertz light generation device comprising a control device for staking.
  2. 　前記レーザ光とテラヘルツ光が同一光軸上に配置するコリニア位相整合によってテラヘルツ光を発生させることを特徴とする請求項１記載のテラヘルツ光発生装置。 2. The terahertz light generating device according to claim 1, wherein the terahertz light is generated by collinear phase matching in which the laser light and the terahertz light are arranged on the same optical axis.
  3. 　前記レーザ光として、波長の異なる２本のレーザ光をポンプ光とする光源を含み、前記２本のポンプ光の周波数の差に相当する周波数を有するテラヘルツ光を発生することを特徴とする請求項１または２記載のテラヘルツ光発生装置。 The laser beam includes a light source that uses two laser beams having different wavelengths as pump light, and generates terahertz light having a frequency corresponding to a difference in frequency between the two pump beams. The terahertz light generator according to 1 or 2.
  4. 　前記制御装置は２本のポンプ光のうち少なくとも１本の周波数を変更する光源波長制御部を含み、周波数変更されたポンプ光によって、テラヘルツ光の周波数を変更することを特徴とする請求項３記載のテラヘルツ光発生装置。 The said control apparatus contains the light source wavelength control part which changes at least 1 frequency among two pump lights, The frequency of terahertz light is changed with the pump light by which the frequency was changed. Terahertz light generator.
  5. 　前記制御装置は、前記周波数変更されたポンプ光の周波数に応じて、前記回転機構を駆動し前記増幅用光学素子を回転せしめる回転制御部を含むことを特徴とする請求項４記載のテラヘルツ光発生装置。 5. The terahertz light generation according to claim 4, wherein the control device includes a rotation control unit that drives the rotation mechanism and rotates the amplification optical element in accordance with the frequency of the pump light whose frequency has been changed. apparatus.
  6. 　発生するテラヘルツ光の強度を検出するセンサを含み、前記回転制御部は発生するテラヘルツ光の強度が最大になるように前記レーザ光の入射角度を微調整することを特徴とする請求項１～５のいずれか１記載のテラヘルツ光発生装置。 6. A sensor for detecting the intensity of the generated terahertz light, wherein the rotation control unit finely adjusts the incident angle of the laser light so that the intensity of the generated terahertz light is maximized. The terahertz light generator according to any one of the above.
  7. 　前記非線形光学結晶は、ＧａＰ、ＺｎＴｅ、ＧａＳｅ、またはＤＡＳＴ（4-dimethylamino-N-methyl-4-stilbazolium tosylate）であることを特徴とする請求項１～６のいずれか１記載のテラヘルツ光発生装置。 7. The terahertz light generator according to claim 1, wherein the nonlinear optical crystal is GaP, ZnTe, GaSe, or DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate). .
  8. 　前記１次元フォトニック結晶の高屈折率及び低屈折率の誘電体層は溶融石英ガラス及びポリエチレンであることを特徴とする請求項１～７のいずれか１記載のテラヘルツ光発生装置。 The terahertz light generating device according to any one of claims 1 to 7, wherein the high refractive index and low refractive index dielectric layers of the one-dimensional photonic crystal are fused silica glass and polyethylene.
  9. 　前記レーザ光の周波数差は０．１～１００ＴＨｚのテラヘルツ周波数帯域にあることを特徴とする請求項１～８のいずれか１記載のテラヘルツ光発生装置。 9. The terahertz light generation device according to claim 1, wherein a frequency difference of the laser light is in a terahertz frequency band of 0.1 to 100 THz.
  10. 　レーザ光の入射によりテラヘルツ帯域の電磁波を放射するテラヘルツ光発生方法であって、
    　高屈折率及び低屈折率の誘電体層が交互に積層された１次元フォトニック結晶の周期方向において非線形光学結晶からなる欠陥層を介在させた増幅用光学素子を用意する工程と、
    　前記１次元フォトニック結晶の周期方向に、少なくとも２つの互いに近傍の周波数を有するレーザ光を同一光軸上に入射させる工程と、
    　前記レーザ光のうち少なくとも１本の周波数を変更する工程と、
    　前記欠陥層を通り前記１次元フォトニック結晶の周期方向に垂直な方向に伸長する回転軸まわりに前記増幅用光学素子を回転せしめ前記レーザ光の入射角度を相対的に変化させることによって、放射される前記電磁波の周波数を変化せしめる粗調工程と、を含むことを特徴とするテラヘルツ光発生方法。
          A terahertz light generation method for emitting terahertz band electromagnetic waves by incidence of laser light,
    Providing an amplification optical element having a defect layer made of a nonlinear optical crystal interposed in a periodic direction of a one-dimensional photonic crystal in which dielectric layers of high refractive index and low refractive index are alternately laminated;
    Allowing at least two laser beams having frequencies close to each other to enter the same optical axis in the periodic direction of the one-dimensional photonic crystal;
    Changing the frequency of at least one of the laser beams;
    The laser beam is emitted by rotating the amplification optical element around a rotation axis extending in a direction perpendicular to the periodic direction of the one-dimensional photonic crystal through the defect layer and relatively changing an incident angle of the laser beam. A terahertz light generating method, comprising: a rough tuning step of changing a frequency of the electromagnetic wave.
PCT/JP2009/062040 2009-07-01 2009-07-01 Terahertz light generating device and method WO2011001521A1 (en)

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WO2012077769A1 (en) * 2010-12-09 2012-06-14 公立大学法人大阪府立大学 Light generation device and light generation method
CN104701713A (en) * 2015-03-25 2015-06-10 天津大学 Photonic crystal fiber THz laser device

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JP2006091802A (en) * 2004-09-21 2006-04-06 Semiconductor Res Found Device and method for terahertz electromagnetic wave generation
JP2009080448A (en) * 2007-09-07 2009-04-16 Kagawa Univ Terahertz light source

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JP2006091802A (en) * 2004-09-21 2006-04-06 Semiconductor Res Found Device and method for terahertz electromagnetic wave generation
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WO2012077769A1 (en) * 2010-12-09 2012-06-14 公立大学法人大阪府立大学 Light generation device and light generation method
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