WO2019167478A1 - Procédé et dispositif de mesure spectroscopique bidimensionnelle - Google Patents

Procédé et dispositif de mesure spectroscopique bidimensionnelle Download PDF

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Publication number
WO2019167478A1
WO2019167478A1 PCT/JP2019/001898 JP2019001898W WO2019167478A1 WO 2019167478 A1 WO2019167478 A1 WO 2019167478A1 JP 2019001898 W JP2019001898 W JP 2019001898W WO 2019167478 A1 WO2019167478 A1 WO 2019167478A1
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Prior art keywords
frequency comb
optical frequency
optical
comb
spectroscopic measurement
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PCT/JP2019/001898
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English (en)
Japanese (ja)
Inventor
薫 美濃島
峰士 加藤
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国立大学法人電気通信大学
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Priority to JP2019509004A priority Critical patent/JP7194438B2/ja
Publication of WO2019167478A1 publication Critical patent/WO2019167478A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry

Definitions

  • the present invention relates to a two-dimensional spectroscopic measurement method and a two-dimensional spectroscopic measurement apparatus.
  • spectroscopic information many techniques such as an imaging method, Fourier transform infrared spectroscopy (FT-IR), and a dispersive infrared spectroscopic method are used. In these methods, it is difficult to obtain two-dimensional spatial information and one-dimensional wavelength information at the same time.
  • FT-IR Fourier transform infrared spectroscopy
  • dispersive infrared spectroscopic method it is difficult to obtain two-dimensional spatial information and one-dimensional wavelength information at the same time.
  • the two-dimensional spatial information and the one-dimensional wavelength information may be collectively referred to as two-dimensional spectral information.
  • Two-dimensional spectroscopy is also called surface spectroscopy or hyperspectral imaging. If two-dimensional spectroscopic information is obtained, for example, an image of an arbitrary wavelength can be extracted from the acquired data, and a celestial body such as a galaxy can be analyzed in detail.
  • two-dimensional spectroscopic information can be acquired by performing FT-IR for each point while scanning each point (a plurality of measurement regions) on the two-dimensional plane.
  • the conventional two-dimensional spectroscopy has a problem that it is difficult to measure a dynamic object because it takes time to sweep the space.
  • two-dimensional spectroscopic information can be acquired at once, spectroscopic measurement of various dynamic objects can be accurately performed.
  • Non-Patent Document 1 discloses a variable bandpass filter that can be applied to a method of acquiring two-dimensional spatial information and one-dimensional wavelength information while sweeping a wavelength band transmitted by a variable bandpass filter. .
  • variable bandpass filter disclosed in Non-Patent Document 1
  • the present invention has been made to solve the above-described problem, and is a two-dimensional spectroscopic measurement method and a two-dimensional spectroscopic measurement that can instantaneously acquire high-resolution spectroscopic information and perform two-dimensional spectroscopic measurement in real time. Providing equipment.
  • the two-dimensional spectroscopic measurement method of the present invention includes a first frequency mode having a predetermined offset frequency with respect to zero on the frequency axis and an integer multiple of a predetermined repetition frequency with respect to the first frequency mode on the frequency axis.
  • the frequency comb is divided into a second optical frequency comb and a third optical frequency comb, the second optical frequency comb is divided into a fourth optical frequency comb and a fifth optical frequency comb, and the fourth optical frequency comb
  • the above-described two-dimensional spectroscopic measurement method further includes a repetition frequency adjustment step of adjusting the repetition frequency according to a phase shift between the fourth optical frequency comb and the fifth optical frequency comb on the time axis. May be.
  • the transmission intensity when the envelope intensity passes through each of the two filters whose wavelength dependences are opposite to each other is acquired.
  • the optical information may be calculated based on the transmission intensity ratio.
  • a predetermined delay time is added to the second optical frequency comb or the third optical frequency comb, and an intensity spectrum including the optical information and A phase spectrum may be acquired.
  • the two-dimensional spectroscopic measurement apparatus includes a first frequency mode having a predetermined offset frequency with respect to zero on the frequency axis and an integer multiple of a predetermined repetition frequency with respect to the first frequency mode on the frequency axis.
  • a first optical frequency comb emitting unit configured to emit a first optical frequency comb having a plurality of second frequency modes arranged at intervals, the repetition frequency being four times the offset frequency, and the first light
  • a first branching unit that divides the frequency comb into a second optical frequency comb and a third optical frequency comb
  • a second branching unit that divides the second optical frequency comb into a fourth optical frequency comb and a fifth optical frequency comb.
  • a phase difference providing unit that shifts the phase on the time axis of the fourth optical frequency comb by 90 ° with respect to the phase on the time axis of the fifth optical frequency comb, and the third optical frequency Comb or the fourth optical frequency comb and
  • the fifth optical frequency comb includes arbitrary optical information, causes the fourth optical frequency comb and the third optical frequency comb to interfere with each other to generate a first interference signal, and the fifth optical frequency comb.
  • An interference signal generator for generating a second interference signal by causing a comb to interfere with the third optical frequency comb; and an envelope for acquiring an envelope strength of the first interference signal and the second interference signal A line intensity acquisition unit; and an optical information extraction unit that extracts the optical information based on the envelope intensity.
  • the envelope intensity acquisition unit includes two filters whose transmittance wavelength dependence is opposite to each other, and the envelope intensity passes through each of the two filters.
  • the optical information extraction unit may calculate the optical information based on the transmission intensity ratio.
  • the above-described two-dimensional spectroscopic measurement apparatus further includes a delay mechanism that adds a predetermined delay time to the second optical frequency comb or the third optical frequency comb, and the optical information extraction unit includes the optical information.
  • the intensity / phase spectrum may be acquired.
  • the optical information is an optical frequency of any one of the third optical frequency comb, the fourth optical frequency comb, and the fifth optical frequency comb.
  • the refractive index distribution on the optical path of the comb, the fluctuation of the refractive index, the path of the third optical frequency comb, or the path of the fourth optical frequency comb and the fifth optical frequency comb Includes any of the sample shapes.
  • a two-dimensional spectroscopic measurement method and a two-dimensional spectroscopic measurement device that instantaneously acquire high-resolution spectroscopic information and enable two-dimensional spectroscopic measurement in real time.
  • FIG. 3 is a schematic diagram of a pulse generation optical system that generates optical frequency combs (optical pulse trains) that are 90 ° out of phase with each other. It is a schematic diagram for demonstrating the time interval of the 1st optical pulse and the 2nd optical pulse on the time axis in an optical frequency comb.
  • FIG. 1 It is a perspective view which shows the mode of permeation
  • FIG. 1 It is a schematic diagram which shows the envelope intensity distribution of the interference signal which the phase mutually shifted 90 degrees.
  • FIG. 1 is a schematic diagram showing an electric field distribution on the time axis (upper stage) and an intensity distribution on the frequency axis (lower stage) of the optical frequency comb.
  • the intensity distribution on the frequency axis represents a spectral distribution.
  • the relationship shown in the equation (1) is established between the repetition time T rep of the optical pulse train oscillated at a constant repetition and the frequency interval f rep .
  • Each optical pulse train is composed of a superposition of many longitudinal modes propagating inside a resonator of the light source.
  • the optical pulse train is composed of a carrier wave, which is a superposition wave of these longitudinal modes, and a wave packet constituting an envelope of the carrier wave.
  • a carrier wave is also called a carrier.
  • the envelope of the carrier wave is also called an envelope.
  • the velocity of the carrier wave and the velocity of the wave packet are different from each other, so that a phase difference occurs with time.
  • the laser resonator is constituted by a dispersion medium.
  • a phase shift ⁇ CEO occurs between adjacent pulses.
  • the period of the phase shift ⁇ CEO is one period at time T CEO .
  • the optical frequency comb is a frequency mode (first frequency mode) having a predetermined carrier envelope offset (CEO, offset frequency) f CEO with respect to zero on the frequency axis. ) F 0 and a plurality of frequency modes (second frequency modes) f m arranged at intervals of an integer multiple of a predetermined repetition frequency f rep with respect to the frequency mode f 0 on the frequency axis.
  • Carrier envelope offset f CEO of the optical frequency comb is equivalent to the reciprocal of the time T CEO.
  • the carrier envelope offset f CEO, shift phi CEO phase, between the time T CEO holds the relationship shown in equation (2).
  • Equation (3) The frequency of the nth spectrum of the optical frequency comb is expressed as shown in Equation (3) using the repetition frequency f rep and the carrier envelope offset f CEO as parameters.
  • the carrier wave and the envelope can be controlled by controlling the parameters related to the plurality of frequency modes of the optical frequency comb based on the above-described correlation.
  • two parameters of the optical frequency comb that is, parameters related to a plurality of frequency modes of the optical frequency comb are controlled so that the repetition frequency f rep and the carrier envelope offset f CEO maintain the relationship of the expression (4). To do.
  • FIG. 2 is a schematic diagram showing the electric field distribution on the time axis of the optical frequency comb in which the repetition frequency f rep and the carrier envelope offset f CEO are controlled so as to maintain the relationship of the expression (4).
  • the same phase and waveform pattern as the reference optical pulse appear in the four optical pulses ahead on the time axis from the reference optical pulse.
  • the relationship of the formula (5) is established between the time T CEO and the carrier envelope offset f CEO .
  • FIG. 3 is a schematic diagram showing an example of an optical system 120 that generates optical pulse trains that are 90 ° out of phase with each other.
  • the optical system 120 includes an optical frequency comb emitting unit 103, a half mirror (second branching unit) 112, a half mirror 118, total reflection mirrors 114 and 116, and a delay applying unit (phase difference). Granting part) 123.
  • the optical frequency comb emitting unit 103 includes a function generator (not shown).
  • the optical frequency comb emitting unit 103 mainly controls the carrier envelope offset f CEO so that the repetition frequency f rep and the carrier envelope offset f CEO keep the relationship of the expression (4) by the operation of the function generator.
  • the envelope offset f CEO is emitted from the controlled optical frequency comb C1.
  • the optical frequency comb C1 passes through the half mirror 112 and is separated into an optical frequency comb C4 and an optical frequency comb C5.
  • the optical frequency comb C4 is reflected by the total reflection mirror 116 and enters the half mirror 118.
  • the optical frequency comb C5 is reflected by the half mirror 112 and the total reflection mirror 114, passes through the delay applying unit 123, and enters the half mirror 118.
  • the delay imparting unit 123 is composed of two total reflection mirrors 121 and 122 with their respective reflecting surfaces facing each other.
  • the optical frequency comb C5 reflected by the total reflection mirror 114 enters the delay applying unit 123, reciprocates a predetermined number of times between the reflection surfaces of the total reflection mirrors 121 and 122 while shifting the optical path, toward the half mirror 118.
  • the positions and the separation distances of the total reflection mirrors 121 and 122 are adjusted so that one phase of the optical frequency combs C4 and C5 incident on the half mirror 118 is shifted by 90 ° with respect to the other phase. That is, in the optical system 120, the optical frequency comb is branched, and one is delayed by an amount corresponding to the time difference between a certain optical pulse and the next optical pulse on the time axis. The time difference between adjacent optical pulses on the time axis corresponds to the repetition time T rep .
  • FIG. 4 shows the first optical pulse ⁇ 1st optical pulse shown in FIG. 3 and FIG. 4> and the second optical pulse ⁇ shown in FIG. 3 and FIG.
  • the repetition frequency f rep of the optical frequency comb C1 is controlled.
  • the repetition time T rep is controlled by controlling the repetition frequency f rep of the optical frequency comb C 1 by operating the function generator of the optical frequency comb emission unit 103. Can be controlled.
  • FIG. 5 is a schematic diagram showing an example of an optical system 124 that can stabilize fluctuations that occur in the optical paths of the optical frequency combs C4 and C5.
  • the optical system 124 includes a half mirror 126 and a feedback mechanism 128 in addition to the configuration of the optical system 120.
  • Half mirror 126 is arranged ahead of half mirror 118 in the direction of travel of optical frequency combs C4 and C5.
  • the feedback mechanism 128 is arranged on the path of optical frequency combs C4 and C5 that are separated by the half mirror 126 and different from the optical frequency combs C4 and C5 that pass through the half mirror 126.
  • the optical frequency combs C4 and C5 combined by the half mirror 118 and including the time difference ⁇ are separated into two by the half mirror 126.
  • One of the separated optical frequency combs (parts of the fourth optical frequency comb and the fifth optical frequency comb) C4 and C5 are reflected by the half mirror 126 and input to the feedback mechanism 128, and the optical frequency comb output unit 103 Feedback.
  • the repetition frequency f rep of the optical frequency comb C1 is adjusted. As shown in FIG.
  • the repetition time T rep of the optical frequency comb C1 emitted from the optical frequency comb emission unit 103 is increased or decreased by the time difference ⁇ .
  • the repetition time T rep with the time difference ⁇ the phase shift between the optical frequency combs C4 and C5 incident on the half mirror 118 is again 90 °, that is, one optical pulse.
  • FIG. 6 is a schematic diagram showing the configuration of an interference intensity signal acquisition optical system 130 that instantaneously obtains interference intensity signals that are 90 ° out of phase with each other, which is an interference signal intensity acquisition apparatus of the present invention.
  • the interference intensity signal acquisition optical system 130 includes an optical frequency comb emission unit 103, a partial optical system 124P, a branching unit 150, a delay mechanism 206, and an imaging camera (envelope intensity acquisition unit) 161.
  • a partial optical system 124P illustrated in FIG. 6 has a configuration in which the optical frequency comb emitting unit 103 is excluded from the optical system 124 illustrated in FIG.
  • the branching unit 150 takes out the optical frequency combs C6 and C7 from the optical frequency comb C3.
  • the branching unit 150 includes a half mirror (interference signal generating unit) 152, half mirrors (first branching units) 153, 155, and 158, and total reflection mirrors 154, 156, and 157.
  • the optical frequency comb emitting unit 103 emits an optical frequency comb (first optical frequency comb) C1 in which the repetition frequency f rep is four times the carrier envelope offset f CEO .
  • the first branching unit 104 divides the optical frequency comb C1 into an optical frequency comb (second optical frequency comb) C2 and an optical frequency comb (third optical frequency comb) C3.
  • the second branching unit 105 divides the optical frequency comb C2 into an optical frequency comb (fourth optical frequency comb) C4 and an optical frequency comb (fifth optical frequency comb) C5 (see FIG. 5).
  • the phase difference providing unit 106 shifts the phase on the time axis of the optical frequency comb C4 and the phase on the time axis of the optical frequency comb C5 by 90 °.
  • the interference signal generation unit 107 generates an interference signal (first interference signal) IM1 by causing the optical frequency comb C4 and the optical frequency comb (third optical frequency comb) C6 including arbitrary optical information to interfere with each other.
  • the frequency comb C5 and an optical frequency comb (third optical frequency comb) C7 including optical information are caused to interfere with each other to generate an interference signal (second interference signal) IM2.
  • the optical information in this specification is added by passing through a sample placed on the optical path, optical characteristics of each optical frequency comb itself, refractive index distribution / fluctuation on the optical path of each optical frequency comb, and so on.
  • This includes all sample shapes.
  • the shape of the sample includes an uneven shape on the surface of the sample, the internal structure of the sample, and the like. That is, according to the interference intensity signal acquisition optical system 130, it is possible to acquire shape information such as the surface of the sample or the internal structure.
  • the optical information is the optical characteristics of the optical frequency comb C3 itself and the optical path of the optical frequency combs C3, C6, C7.
  • the optical information mainly includes optical characteristics including the shape of the sample S.
  • the envelope strength acquisition unit 108 acquires the envelope strength EV of the interference signal IM1 and the interference signal IM2.
  • the optical frequency comb C1 emitted from the optical frequency comb emission unit 103 is separated into optical frequency combs C2 and C3 by a half mirror 153.
  • the optical frequency comb C2 enters the partial optical system 124P and exits as optical frequency combs C4 and C5 whose phases are shifted by 90 ° as described above.
  • the optical frequency comb C3 reflected by the half mirror 153 enters the branching unit 150, is reflected by the total reflection mirror 154, and is separated by the half mirror 155 into optical frequency combs C6 and C7.
  • the delay mechanism 206 is a mechanism for adding a predetermined delay time to the optical frequency comb C3, and is arranged on the path of the optical frequency comb C3. As shown in FIG. 7, the delay mechanism 206 includes two total reflection prisms 207 in which respective reflection surfaces 207 r are arranged to face each other. As the delay mechanism 206 moves along the arrow M, the optical path length of the optical frequency comb C3 changes and a predetermined delay time is added.
  • FIG. 8 is a schematic diagram showing the state of reflection of the optical frequency comb C4 and transmission of the optical frequency comb C5 at the half mirror 118 of the partial optical system 124P (that is, the optical system 124).
  • the optical frequency comb C4 is incident on the reflection surface 118a of the half mirror 118, and is reflected substantially at right angles to the incident direction when viewed from above.
  • the optical frequency comb C5 transmits the surface 118b and the reflective surface 118a opposite to the reflective surface 118a of the half mirror 118, and overlaps the path of the optical frequency comb C4 in top view. The light is emitted from the half mirror 118 along the course. In the height direction, the paths of the optical frequency combs C4 and C5 are shifted from each other.
  • FIG. 9 is a schematic diagram showing a state of reflection of the optical frequency comb C6 and transmission of the optical frequency comb C7 in the half mirror 158 of the branching unit 150.
  • the optical frequency comb C6 is incident on the reflecting surface 158a of the half mirror 158 and is reflected substantially at right angles to the incident direction in a top view.
  • the optical frequency comb C7 transmits the surface 158b and the reflective surface 158a opposite to the reflective surface 158a of the half mirror 158, and overlaps the path of the optical frequency comb C6 in top view. The light is emitted from the half mirror 158 along the course.
  • the paths of the optical frequency combs C6 and C7 are shifted from each other.
  • the height of the path of the optical frequency comb C6 matches the height of the optical frequency comb C4, and the height of the optical frequency comb C7 matches the height of the optical frequency comb C5.
  • FIG. 10 is a schematic diagram showing a state of transmission of the optical frequency combs C4 and C5 and reflection of the optical frequency combs C6 and C7 in the half mirror 152 of the branching unit 150.
  • the optical frequency combs C ⁇ b> 4 and C ⁇ b> 5 emitted from the half mirror 118 pass through the surface 152 b on the opposite side of the reflection surface 152 a of the half mirror 152.
  • the optical frequency combs C6 and C7 emitted from the half mirror 158 are reflected by the reflecting surface 152a of the half mirror 152 at a substantially right angle with respect to the incident direction in a top view and transmitted through the surface 152b.
  • Interference signals IM1 and IM2 are generated.
  • the interference signal IM1 is an interference signal between the optical frequency combs C4 and C6, and the interference signal IM2 is an interference signal between the optical frequency combs C5 and C7.
  • the irradiation positions of the optical frequency combs C4 and C6 in the half mirror 118 are made different from each other, and the irradiation positions of the optical frequency combs C5 and C7 in the half mirror 158 are mutually different. Make it different. Accordingly, the position where the optical frequency combs C4 and C6 are overlapped to generate the interference signal IM1 is different from the position where the optical frequency combs C5 and C7 are overlapped to generate the interference signal IM2.
  • FIG. 11 is a graph showing an example of the envelope intensity EV obtained from the interference signals IM1 and IM2. If the intensity T1 of the interference signal IM1 and the intensity T2 of the interference signal IM2 at a certain moment are acquired by the imaging camera 161, the envelope intensity EV is calculated by calculating ⁇ (T1) 2 + (T2) 2 ⁇ 1/2. Can be obtained instantly.
  • the envelope intensity EV is detected by the imaging camera 161.
  • the envelope intensity EV detected by the imaging camera 161 is appropriately processed by a processing unit (not shown) attached to the imaging camera 161.
  • the processing unit is, for example, a program built in a computer connected to the imaging camera 161.
  • the envelope intensity EV of the interference signals IM1 and IM2 whose phases are shifted from each other by 90 ° can be instantaneously obtained.
  • FIG. 12 is a schematic diagram showing the configuration of the two-dimensional spectroscopic measurement apparatus 200 of the present invention.
  • the two-dimensional spectroscopic measurement apparatus 200 includes a wavelength information acquisition unit 208 in place of the single imaging camera 161 in addition to the configuration of the interference intensity signal acquisition optical system 130 described above.
  • the optical frequency combs C4 and C5 are fed back to the optical frequency comb output unit 103 by the feedback mechanism 128, and the phase shift from the optical frequency combs C4 and C5 (time difference ⁇ , see FIG. 3). Accordingly, the repetition frequency f rep is adjusted.
  • the wavelength information acquisition unit 208 includes a half mirror 231, a total reflection mirror 232, filters F1 and F2, two imaging cameras 241 and 242 having the same number of pixels, and an image processing unit (optical information extraction unit) 250.
  • the total reflection mirror 154 of the interference intensity signal acquisition optical system 130 is replaced with a half mirror 159.
  • the sample S that is the object of spectroscopic measurement is arranged on the path of the optical frequency comb C3 that passes through the half mirror 159.
  • the optical frequency comb C3 reflected by the half mirror 153 passes through the half mirror 159 and is irradiated onto the sample S.
  • the optical frequency comb C3 reflected from the sample S includes optical information including all the spectral information and phase / shape information of the sample S.
  • the optical information of the sample S is also included in the optical frequency combs C6 and C7 divided into two by the half mirror 155 from the optical frequency comb C3.
  • the optical information of the sample S is reflected in the interference signals IM1 and IM2.
  • the envelope strength EV of the interference signals IM1 and IM2 is divided into two by the half mirror 231, and the two divided envelope strengths EV1 and EV2 pass through the filters F1 and F2, respectively.
  • FIG. 13 is a graph showing the wavelength dependence of the transmittance of the filters F1 and F2. As shown in FIG. 13, the wavelength dependences of the transmittances of the filters F1 and F2 are opposite to each other.
  • the transmittance of the filter F1 generally decreases as the wavelength increases.
  • the transmittance of the filter F2 generally increases as the wavelength increases.
  • the wavelength dependency of the transmittance of the filters F1 and F2 is opposite to each other, so that there is a one-to-one correspondence between the light intensity ratio and the wavelength for the envelope intensities EV1 and EV2 that have passed through the filters F1 and F2. Is established.
  • the image processing unit 50 calculates the ratio of the transmission intensities of the envelope strengths EV1 and EV2 for each measurement region of the sample S acquired by the imaging cameras 241 and 242 through the filters F1 and F2. Based on the ratio of the transmission intensity of the envelope intensity EV1 and EV2 calculated for each pixel of the imaging cameras 241 and 242, the signal intensity ratio of each pixel is obtained, and the wavelength expressing each intensity in the distribution of the envelope intensity EV is Determined instantly.
  • the phase information of the optical frequency comb C3 reflected from the sample S at each spatial position (measurement region) is measured.
  • the phase information of the optical frequency comb C3 is a time difference and indicates a physical position difference and a refractive index difference. In this embodiment, when the physical position is acquired instantaneously, it is assumed that the phase spectrum of the optical frequency comb C6 reflected from the sample S basically does not change.
  • the two-dimensional spectroscopic measurement method of the present invention includes an optical frequency comb generation step, a phase difference providing step, a sample irradiation step, an interference signal generation step, an envelope intensity acquisition step, and an optical information extraction step.
  • the envelope intensity EV of the interference signals IM1 and IM2 is instantaneously acquired using the two-dimensional spectroscopic measurement apparatus 200, and the sample S is based on the acquired envelope intensity EV. It is a method that can obtain the optical information.
  • optical frequency comb C1 is generated (see FIG. 1).
  • Optical frequency comb C1 is a frequency mode f 0 having a predetermined carrier envelope offset f CEO against zero on the frequency axis, of the predetermined relative frequency mode f 0 the frequency axis repetition frequency f rep integral multiple of the A plurality of frequency modes f m arranged at intervals.
  • the carrier envelope envelope offset f CEO and the repetition frequency f rep are controlled using a function generator of the optical frequency comb emitting unit 103 or the like.
  • the optical frequency comb C1 is divided into the optical frequency comb C2 and the optical frequency comb C3 by the half mirror 153, and the optical frequency comb C2 is further divided into the optical frequency comb C4 by the half mirror 112 (see FIG. 3).
  • the delay applying unit 123 shifts the phase of the optical frequency comb C5 on the time axis by 90 ° with respect to the phase of the optical frequency comb C4 on the time axis.
  • the sample S is irradiated with the optical frequency comb C3 or the optical frequency combs C4 and C5, and the optical frequency comb C3 or the optical frequency combs C4 and C5 which are emitted from the sample S and include optical information are obtained.
  • the optical frequency comb C3 or the optical frequency combs C4 and C5 includes arbitrary optical information.
  • the optical frequency comb C4 and the optical frequency comb C6 including optical information in any one of them are caused to interfere with each other to generate an interference signal IM1.
  • the optical frequency comb C5 and the optical frequency comb C7 including optical information in any one of them are caused to interfere with each other to generate an interference signal IM2.
  • the interference signals IM1 and IM2 are simultaneously detected by the imaging camera 161 to obtain the envelope strength EV.
  • the optical information of the sample S is extracted based on the envelope intensity EV.
  • the envelope strength EV is divided into two envelope strengths EV1 and EV2, and the transmission strength when the envelope strengths EV1 and EV2 pass through the filters F1 and F2, respectively, is imaged. Obtained by the cameras 241 and 242.
  • wavelength information regarding the sample S is acquired instantaneously based on the ratio of the transmission intensities of the envelope strengths EV1 and EV2 acquired in the envelope intensity acquisition step, and the optical information of the sample S is obtained from the wavelength information described above by the image processing unit 250. Is calculated.
  • the two-dimensional spectroscopic information or the three-dimensional shape of the sample S can be calculated by comparing with the relationship between the wavelength information obtained from the intensity ratio measured in advance and the delay distance.
  • the two-dimensional spectroscopic measurement method of this embodiment further includes a frequency adjustment step in addition to the above-described steps.
  • a frequency adjustment step a part of the optical frequency combs C4 and C5 is fed back to the optical frequency comb output unit 103 by the feedback mechanism 128, and the phase shift from the optical frequency combs C4 and C5 (time difference ⁇ , see FIG. 3) To adjust the repetition frequency f rep .
  • the two-dimensional spectroscopic measurement method of the present embodiment includes the above-described optical frequency comb generation step, phase difference application step, interference signal generation step, envelope intensity acquisition step, and optical information extraction step.
  • the two-dimensional spectroscopic measurement apparatus 200 of this embodiment includes the above-described optical frequency comb emitting unit 103, the first branching unit 104, the second branching unit 105, the phase difference providing unit 106, and the interference signal generating unit 107. And an envelope strength acquisition unit 108 and an image processing unit 250.
  • the optical frequency comb whose rep is controlled is divided into two to generate optical frequency combs whose phases are shifted from each other by 90 °.
  • Two optical frequency combs that are 90 ° out of phase with each other are optical pulse trains that function as reference light. Each of these two optical frequency combs interferes with an optical frequency comb including arbitrary optical information, and an interference signal whose phase is shifted by 90 ° is optically generated in real time.
  • the optical frequency comb including arbitrary optical information is an optical pulse train that functions as probe light.
  • the envelope strength of the interference signal can be acquired instantaneously and in real time during measurement.
  • the repetition frequency f rep and the carrier envelope offset f CEO are controlled with the same degree of stability and accuracy as the atomic clock.
  • the carrier envelope offset f CEO the phase difference between the adjacent optical pulses on the time axis can be utilized, and in principle, the phase difference can be accurately aligned in the entire wavelength range to be measured. .
  • high-resolution spectroscopic information can be acquired instantaneously, and two-dimensional spectroscopic measurement can be performed in real time.
  • the fourth optical frequency comb and the fifth optical frequency comb are fed back to the optical frequency comb emitting unit 103, and the fourth optical frequency comb and the second optical frequency comb are combined.
  • the repetition frequency f rep is adjusted according to the phase shift (time difference ⁇ ) with respect to the optical frequency comb 5.
  • the phase shift between the optical frequency combs of the reference light can be eliminated.
  • the optical path variation of the optical frequency comb can be optically compensated without adding a mechanically driven configuration such as a piezo element to the optical system.
  • the optical information of the sample S is calculated based on the ratio of the transmission intensity of the acquired envelope intensities EV1 and EV2.
  • an intensity / phase spectrum including optical information can be acquired by adding a predetermined delay time to the optical frequency comb C3 by the delay mechanism 206.
  • the optical information obtained by the two-dimensional spectroscopic measurement method and the two-dimensional spectroscopic measurement apparatus 200 of the present embodiment includes the distribution and fluctuation of the refractive index on the optical path of the optical frequency comb C3 or the optical frequency combs C4 and C5, and the shape of the sample S.
  • the three-dimensional shape of the sample S is included. According to the two-dimensional spectroscopic measurement method and the two-dimensional spectroscopic measurement apparatus 200 of the present embodiment, since the three-dimensional shape of the sample S can be acquired based on the envelope strength EV, instantaneous and real-time three-dimensional shape measurement is realized, It can be applied to a wide range of fields including astronomy and physical properties.
  • the optical information of the sample S is given to the optical frequency comb C3.
  • the optical information of the sample S is changed to the optical frequency comb C3. May be given to the optical frequency combs C4 and C5.
  • the polarizations of the optical frequency combs C4 and C5 are multiplexed so as to be orthogonal to each other, and after passing through the sample S, are demultiplexed.
  • interference signals (first interference signal, second interference signal) between the optical frequency combs C4 and C5 including the optical information of the sample S and the optical frequency combs C6 and C7 not including the optical information of the sample S
  • first interference signal second interference signal
  • the optical information of the sample S does not have polarization dependency and can be acquired without considering the polarization dependency.
  • the optical frequency comb C3 reflected from the sample S is acquired.
  • the optical frequency comb C3 transmitted from the sample S by irradiating the sample S with the optical frequency comb C3 is obtained. You may get it.
  • the half mirror 159 may be replaced with a total reflection mirror, and the sample S may be disposed between the total reflection mirror and the half mirror 155 in which the sample S is replaced as described above on the path of the optical frequency comb C3.
  • the phase spectrum of the optical frequency comb C3 reflected from the sample S may change with respect to the wavelength.
  • the change of the phase spectrum of the optical frequency comb C3 in that case must be uniquely determined with respect to the wavelength.
  • the phase spectrum related to the sample S can be obtained by adding a time delay to the optical frequency comb C3 or the optical frequency comb C1 and measuring the delay time dependence of the intensity of the interference signals IM1 and IM2.
  • the delay mechanism 206 is disposed either on the path of the optical frequency comb C3 between the half mirrors 153 and 159 or on the path of the optical frequency comb C2 between the half mirrors 153 and 112, Good.
  • the configuration of the delay mechanism 206 is not particularly limited as long as a predetermined delay time can be added to a predetermined optical frequency comb.
  • the optical frequency comb C3 is given a delay time derived from the shape of the sample S when the sample S is transmitted or reflected.
  • the optical frequency comb C3 to which the delay time is given is measured by the two-dimensional spectroscopic measurement apparatus 200 of the above-described embodiment excluding the delay mechanism 206, whereby the sample
  • the delay time derived from the shape of S can be instantaneously acquired as wavelength information. Acquiring such wavelength information is the same as performing instantaneous three-dimensional shape measurement of the sample S.
  • depth information that is, a three-dimensional shape
  • the optical information of the sample S obtained by the two-dimensional spectroscopic measurement method and the two-dimensional spectroscopic measurement apparatus of the present invention is a three-dimensional shape as long as the time for the optical pulse train of the optical frequency comb to reach the interference signal generation unit is shifted. It is not limited to.
  • the optical information of the sample S obtained by the two-dimensional spectroscopic measurement method and the two-dimensional spectroscopic measurement apparatus of the present invention includes, for example, a refractive index fluctuation.
  • the configuration of the wavelength information acquisition unit and the optical information extraction unit and the processing content by the program of the processing unit can be appropriately changed.
  • the optical frequency combs C4, C5, C6, and C7 may be chirped.
  • an appropriate dispersion medium is installed on the optical path of each of the optical frequency combs C2 and C3 that are the sources of these optical frequency combs, and light is transmitted to the dispersion medium.
  • the frequency combs C2 and C3 may be passed.
  • the optical frequency combs C4, C5, C6, and C7 are chirped through the dispersion medium in this way, the interference signals IM1 and IM2 do not change, so that the same effects as those of the above-described embodiment can be obtained.
  • Optical frequency comb (first optical frequency comb)
  • C2 Optical frequency comb (second optical frequency comb)
  • C3 Optical frequency comb (third optical frequency comb)
  • C4 Optical frequency comb (fourth optical frequency comb)
  • C5 Optical frequency comb (fifth optical frequency comb)
  • C6 Optical frequency comb (third optical frequency comb)
  • C7 Optical frequency comb (third optical frequency comb) S ... Sample

Abstract

L'invention concerne un procédé de mesure spectroscopique bidimensionnelle, consistant à générer un premier peigne de fréquence optique dans lequel une fréquence de répétition correspond à quatre fois une fréquence de décalage, à diviser le premier peigne de fréquence optique en deuxième à cinquième peignes de fréquence optique, et à décaler les unes des autres les phases du quatrième peigne de fréquence optique et du cinquième peigne de fréquence optique de 90° sur un axe de temps. Selon le procédé de mesure spectroscopique bidimensionnelle, l'intensité d'enveloppe des éléments suivants est acquise : un signal d'interférence des troisième et quatrième peignes de fréquence optique dans lequel l'un quelconque desdits peignes de fréquence optique comprend des informations optiques concernant un échantillon ; et un signal d'interférence des troisième et cinquième peignes de fréquence optique dans lequel l'un quelconque desdits peignes de fréquence optique comprend des informations optiques concernant un échantillon. Les informations optiques concernant l'échantillon sont ensuite extraites sur la base de la force d'enveloppe.
PCT/JP2019/001898 2018-03-02 2019-01-22 Procédé et dispositif de mesure spectroscopique bidimensionnelle WO2019167478A1 (fr)

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Citations (7)

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US20110069309A1 (en) * 2009-09-18 2011-03-24 Newbury Nathan R Comb-based spectroscopy with synchronous sampling for real-time averaging
JP2011529180A (ja) * 2008-07-25 2011-12-01 サントル ナシオナル ドゥ ラ ルシェルシェサイアンティフィク（セエヌエールエス） 周波数コムを有する同期方式の干渉計
JP2012013574A (ja) * 2010-07-01 2012-01-19 Optical Comb Inc 光学式計測装置及びその干渉計用プリズム。
JP2013507005A (ja) * 2009-10-02 2013-02-28 イムラ アメリカ インコーポレイテッド モード同期レーザによる光信号処理
JP2015155822A (ja) * 2014-02-20 2015-08-27 株式会社東京精密 光信号生成装置、距離測定装置、分光特性測定装置、周波数特性測定装置及び光信号生成方法
JP2017090259A (ja) * 2015-11-10 2017-05-25 国立大学法人電気通信大学 屈折率補正法、距離測定法及び距離測定装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7123402B1 (en) * 2006-01-17 2006-10-17 Lucent Technologies Inc. Cloning optical-frequency comb sources
JP2011529180A (ja) * 2008-07-25 2011-12-01 サントル ナシオナル ドゥ ラ ルシェルシェサイアンティフィク（セエヌエールエス） 周波数コムを有する同期方式の干渉計
US20110069309A1 (en) * 2009-09-18 2011-03-24 Newbury Nathan R Comb-based spectroscopy with synchronous sampling for real-time averaging
JP2013507005A (ja) * 2009-10-02 2013-02-28 イムラ アメリカ インコーポレイテッド モード同期レーザによる光信号処理
JP2012013574A (ja) * 2010-07-01 2012-01-19 Optical Comb Inc 光学式計測装置及びその干渉計用プリズム。
JP2015155822A (ja) * 2014-02-20 2015-08-27 株式会社東京精密 光信号生成装置、距離測定装置、分光特性測定装置、周波数特性測定装置及び光信号生成方法
JP2017090259A (ja) * 2015-11-10 2017-05-25 国立大学法人電気通信大学 屈折率補正法、距離測定法及び距離測定装置

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