Single-comb spectrometer

Abstract

To conduct spectroscopic analysis with a high frequency resolution comparable to dual-comb spectroscopy by a single laser light source.SOLUTION: This single-comb spectrometer comprises: a CW laser light source 5; a light modulation unit 6 for phase modulating a laser beam from the CW laser light source 5 with a prescribed repetition frequency and generating an electro-chemical modulation comb; a broadband light generation unit 2 for causing broadband light to be generated from the electro-chemical modulation comb; a CEO signal detection unit 4a for detecting a CEO signal that indicates the CEO frequency of the broadband light; a feedback circuit 4b for modulating the light frequency of the CW laser light source 5 on the basis of the CEO frequency; and a spectroscopic measurement unit 3 for obtaining spectroscopic data from the result of observation of the broadband light having passed through a sample.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a single-comb spectroscopic device that performs precision spectroscopy using an electro-optic modulation comb. [Background technology]

[0002] Conventional spectrometers can be broadly divided into two types: dispersive and Fourier spectroscopy. Dispersive spectrometers use dispersive elements such as prisms and diffraction gratings to separate the optical spectrum in space and measure the intensity of each wavelength sequentially. Dispersive spectrometers have the problem that they cannot achieve high wavelength resolution due to the limitations of the dispersive elements, and because they measure the intensity for each wavelength, it takes a long time to measure a wide spectral band.

[0003] Fourier spectroscopy spectrometers have the advantage over dispersive spectrometers of being able to simultaneously disperse multiple wavelengths with a single detector, and are widely used in molecular spectroscopy in the infrared wavelength range, etc. However, the frequency resolution and data acquisition speed of Fourier spectroscopy spectrometers are determined by the movement distance and speed of the delay stage, and since mechanical stage movement has reached its limit, there has been a limit to how much performance can be improved.

[0004] Dual-comb spectroscopy, which has attracted attention in recent years, uses two mode-locked (ML) laser light sources with slightly different repetition rates. Because the repetition rates are slightly different, the relative phase of the two beams can be varied without moving the delay stage. This reduces data acquisition time by an order of magnitude compared to Fourier spectroscopy. Furthermore, the amount of relative phase change can be made large, which allows for higher frequency resolution (see Non-Patent Document 1).

[0005] Although dual-comb spectroscopy is a high-speed, high-resolution spectroscopy method, it requires highly advanced technology, as it requires highly accurate synchronization of the repetition rates and phases of two ML lasers using a complex control mechanism. For this reason, dual-comb spectroscopy has only been performed at a few advanced ML laser research institutes, posing a barrier to widespread adoption of high-speed, precise spectroscopy using optical combs. Furthermore, to further shorten measurement times, it is necessary to further increase the repetition rate of the ML laser, but the repetition rate of optical resonator-based ML lasers is limited to a few GHz. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] IAN CODDINGTON, NATHAN NEWBURY, AND WILLIAM SWANN, “Dual-comb spectroscopy”, Vol. 3, No. 4, April 2016, Optica Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a single-comb spectroscopy device that can easily perform precision spectroscopy with a single laser light source at a frequency resolution as high as that of conventional dual-comb spectroscopy. [Means for solving the problem]

[0008] The single-comb spectroscopic device of the present invention comprises a continuous-wave laser light source, a first modulator configured to phase-modulate laser light from the continuous-wave laser light source at a predetermined repetition rate to generate an electro-optic modulation comb, a detection unit configured to detect the carrier envelope offset frequency of the electro-optic modulation comb, a feedback circuit unit configured to modulate the optical frequency of the continuous-wave laser light source based on the carrier envelope offset frequency, a spectroscopic measurement unit configured to obtain spectroscopic data from the observation results of the electro-optic modulation comb transmitted through a sample, a digitizer configured to acquire the spectroscopic data in synchronization with a carrier envelope offset signal indicating the carrier envelope offset frequency, and a data accumulation device configured to output data of the carrier envelope offset frequency, wherein the digitizer performs labeling to add data of the carrier envelope offset frequency to the spectroscopic data.

[0009] Furthermore, in one configuration example of the single-comb spectrometer of the present invention, the feedback circuit section is characterized in that it modulates the optical frequency of the continuous wave laser light source by changing the injection current value of the continuous wave laser light source. Furthermore, one configuration example of the single-comb spectroscopic device of the present invention is characterized in that it further includes a second modulator consisting of a single-sideband electro-optical modulator or an acousto-optical element, arranged downstream of the continuous-wave laser light source, and the feedback circuit section modulates the optical frequency of the continuous-wave laser light source by controlling the second modulator. Furthermore, in one configuration example of the single-comb spectrometer of the present invention, the feedback circuit section is characterized in that it modulates the optical frequency of the continuous wave laser light source so that the carrier envelope offset frequency changes continuously by the repetition frequency. In addition, in one configuration example of the single-comb spectrometer of the present invention, the feedback circuit section is characterized by being composed of a frequency modulation signal generator configured to output a frequency modulation signal, a frequency divider configured to divide the carrier envelope offset signal, and a frequency modulation feedback circuit configured to output a frequency control signal for modulating the optical frequency of the continuous wave laser light source based on the result of comparing the frequency modulation signal with the output signal of the frequency divider.

[0010] In addition, the single comb spectroscopic device of the present invention comprises a continuous wave laser light source configured to continuously change the optical frequency, a modulator configured to phase modulate the laser light from the continuous wave laser light source at a predetermined repetition frequency to generate an electro-optic modulation comb, a detection unit configured to detect the carrier envelope offset frequency of the electro-optic modulation comb, a spectroscopic measurement unit configured to obtain spectroscopic data from the observation results of the electro-optic modulation comb that has passed through a sample, a digitizer configured to acquire the spectroscopic data in synchronization with a carrier envelope offset signal that indicates the carrier envelope offset frequency, and a data accumulation device configured to output data of the carrier envelope offset frequency, wherein the digitizer performs labeling to add data of the carrier envelope offset frequency to the spectroscopic data. In one configuration example of the single-comb spectrometer of the present invention, the continuous wave laser light source is characterized in that the optical frequency changes continuously by the repetition frequency.

[0011] Furthermore, one configuration example of the single-comb spectroscopic device of the present invention further includes a dispersion medium configured to convert the electro-optic modulation comb into an optical pulse train by applying chromatic dispersion to the electro-optic modulation comb, a dispersion compensator configured to shorten the pulse width of the optical pulse train by compressing the pulse width, and a nonlinear medium configured to expand the bandwidth of the optical pulse train output from the dispersion compensator, and the spectroscopic measurement unit is configured to measure the optical pulses whose bandwidth is expanded by the nonlinear medium. Lightis incident on the sample. [Effects of the Invention]

[0012] Because electro-optical comb-based single-comb spectroscopy can precisely control the optical frequency of the electro-optical comb seed light source, this invention enables precise spectroscopy with a single continuous-wave laser light source at a frequency resolution comparable to that of conventional dual-comb spectroscopy. Furthermore, because the spectroscopic data acquisition time of this invention is determined by the sweep speed of the line sensor in the spectroscopic measurement unit, spectroscopic measurements can be expected to be completed in an order of magnitude shorter than conventional dual-comb spectroscopy. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram showing an electro-optic modulation comb. [Figure 2] FIG. 2 is a schematic diagram showing the basic configuration of a single-comb spectrometer according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram illustrating an example of the configuration of a single-comb spectrometer according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of a single-comb spectrometer according to a third embodiment of the present invention. [Figure 5] FIG. 5 is a diagram illustrating an example of the configuration of a single-comb spectrometer according to a fourth embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing another example of the configuration of a single-comb spectroscopic device according to the fourth embodiment of the present invention. [Figure 7] FIG. 7 is a diagram illustrating an example of the configuration of a single-comb spectrometer according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Principle of the Invention] To overcome the problems of the dual-comb spectroscopy described above, the present invention proposes a single-comb spectroscopy device that uses a CW (Continuous Wave) semiconductor laser as a seed light source instead of an ML laser to rapidly modulate the semiconductor laser using the carrier envelope offset (CEO) frequency of an electro-optic (EO) comb.

[0015] FIG. 1 is an explanatory diagram showing an EO comb. As shown in FIG. 1, the EO comb has a repetition frequency f rep This is a collection of many modes arranged in a comb-like pattern on the frequency axis. This collection of laser beams arranged in a comb-like pattern on the frequency axis is called an EO comb. The spectral frequency f n is the CEO frequency, f CEO Then, f n =f ceo +n×f rep (n is an integer).

[0016] The present invention combines broadband, high resolution, high speed, and simplicity, and does not require advanced phase synchronization of the laser as in conventional methods. Therefore, it can be easily handled by people other than laser experts, and it realizes a spectroscopic device that can be used in field environments, enabling high-resolution, high-speed real-time measurements.

[0017] [First Example]

[0023] The following describes in detail embodiments of the present invention. Fig. 2 is a schematic diagram showing the basic configuration of a single-comb spectrometer according to a first embodiment of the present invention. The single-comb spectrometer includes an EO comb generator 1, a broadband light generator 2, a spectroscopic measurement unit 3, a CEO signal detector 4a, and a feedback circuit 4b.

[0018] The EO comb generator 1 generates an EO comb and applies dispersion to the EO comb to generate optical pulses. The optical pulses output from the EO comb generator 1 are input to the broadband light generator 2, which generates broadband light by inducing nonlinear effects (self-phase modulation, cross-phase modulation, etc.). This broadband light is used by the spectroscopic measurement unit 3 to acquire spectroscopic data.

[0019] The EO comb mode spacing can be set arbitrarily using a signal generator, and the bandwidth can be broadened by widening the mode spacing, but the resolution is insufficient for precision spectroscopy such as molecular spectroscopy. Therefore, it is necessary to interpolate the EO comb mode spacing.

[0020] In this embodiment, the broadband light output from the broadband light generator 2 is input to the CEO signal detector 4a to detect the CEO signal. If the CEO frequency and repetition rate of the EO comb can be measured with an RF frequency counter, the optical frequency of the continuous wave (CW) laser light source inside the EO comb generator 1 can be measured with the accuracy of an RF frequency counter, enabling precise spectroscopy with just one EO comb. By high-speed frequency modulation of the CW laser light source using the CEO frequency and the feedback circuit 4b, the EO comb mode spacing can be interpolated, enabling wideband and high-speed single-comb spectroscopy.

[0021] [Second Example] Next, a second embodiment of the present invention will be described. Fig. 3 is a diagram showing an example of the configuration of a single-comb spectrometer according to the second embodiment of the present invention. This embodiment shows a specific example of the first embodiment.

[0022] The EO comb generation unit 1 is composed of a CW laser light source 5 made of a semiconductor laser, an optical modulation unit 6 (first modulator), a signal generator 7, and a dispersion medium 8. The broadband light generating unit 2 comprises an optical amplifier 9 , a dispersion compensator 10 , and a highly nonlinear medium 11 .

[0023] The spectroscopic measurement unit 3 is composed of an optical demultiplexer 12, diffraction gratings 13-1 and 13-2, line sensors 14-1 and 14-2, and a digitizer 16. The CEO signal detector 4 a is composed of a self-referencing interferometer 17 and an RF frequency counter 21 . The feedback circuit section 4b is composed of a frequency divider 18, a frequency modulation signal generator 19, and a frequency modulation feedback circuit 20.

[0024] The EO comb generator 1 uses a CW laser light source 5 as a seed light source for the EO comb. The CW laser light source 5 generates CW light of a wavelength that is included in the optical absorption spectrum of the spectroscopic sample 15. The CW light output from the CW laser light source 5 is incident on the optical modulator 6.

[0025] The optical modulation unit 6 includes an intensity modulator and a phase modulator. The intensity modulator and the phase modulator receive a signal from a signal generator 7, for example, at a frequency f rep The optical modulator 6 is driven by a sinusoidal microwave signal S1 having a repetition rate of f = 25 GHz. rep and phase modulated at a repetition frequency of f rep The EO comb with a frequency mode spacing of

[0026] The dispersion medium 8 such as a single-mode fiber applies wavelength dispersion to the EO comb emitted from the optical modulation unit 6, thereby dispersing the EO comb at a repetition frequency of f rep The optical pulse train transmitted through the dispersive medium 8 is incident on the broadband light generating unit 2.

[0027] Optical amplifier 9 in broadband light generating unit 2 amplifies the optical pulse train. Dispersion compensator 10 shortens the pulse width of the optical pulse train amplified by optical amplifier 9 by using a dispersive medium. The high-power short optical pulse train output from dispersion compensator 10 is incident on highly nonlinear medium 11, such as a highly nonlinear fiber, photonic crystal fiber, silicon wire waveguide, or silicon wire waveguide.

[0028] The highly nonlinear medium 11 broadens the bandwidth of the high-power short optical pulse train. The broadband light whose bandwidth has been broadened by the highly nonlinear medium 11 enters the spectroscopic measurement unit 3 and the CEO signal detection unit 4a.

[0029] The optical splitter 12 of the spectroscopic measurement unit 3 splits the broadband light into two beams. The diffraction grating 13-1 splits the reference light, which is one of the beams split by the optical splitter 12, into beams in different directions for each wavelength. The line sensor 14-1 receives the light split by the diffraction grating 13-1 and outputs an electrical signal (reference signal) S ref Convert to.

[0030] The other light beam split by the optical splitter 12 is incident on the spectroscopic sample 15. The diffraction grating 13-2 splits the light beam transmitted through the spectroscopic sample 15 into different directions for each wavelength. The line sensor 14-2 receives the light beam split by the diffraction grating 13-2 and outputs an electrical signal (spectroscopic signal) S sp Convert to.

[0031] The digitizer 16 converts the received light signal S obtained by the line sensor 14-2 into sp The reference signal S obtained by the line sensor 14-1 ref By normalizing the intensity of the absorption spectrum of the spectroscopic sample 15, it is possible to obtain an absorption spectrum of the spectroscopic sample 15 with a high signal-to-noise ratio.

[0032] On the other hand, the self-referencing interferometer 17 of the CEO signal detection unit 4a receives the broadband light from the highly nonlinear medium 11 of the broadband light generation unit 2 and detects the CEO frequency f CEO CEO signal S CEO The self-referencing interferometer 17 generates an optical interference signal of high-frequency components and low-frequency components contained in the broadband light, photoelectrically converts the generated optical interference signal, and detects the CEO signal S from the obtained electrical signal. CEO It has the function of outputting.

[0033] In this embodiment, the CEO frequency f CEO is the repetition rate of the EO comb, f rep For example, the frequency of the signal generator 7 is changed to 25 GHz (=f rep ), the mode spacing of the EO comb is 25 GHz. Therefore, the CEO frequency f CEOHowever, there is no signal generator capable of high-speed modulation of a wide bandwidth such as 25 GHz, so the CEO signal S CEO The frequency is divided by N (N is an integer of 2 or more) by a frequency divider 18 to convert the frequency downward.

[0034] The frequency modulation signal generator 19 of the feedback circuit section 4b is CEO The reference value of f is used as the reference frequency. rep The frequency modulation signal S repeats continuous frequency changes with a modulation width of / N. MOD1 As will be described later, the frequency modulation signal S MOD1 The frequency of varies according to the control from the digitizer 16.

[0035] The frequency modulation feedback circuit 20 of the feedback circuit section 4b receives the frequency modulation signal S MOD1 and the output signal of the frequency divider 18 are compared in phase, and the frequency control signal S CTL1 The frequency control signal S CTL1 is the optical frequency of the CW laser light source 5, rep Specifically, it is a signal for changing the injection current value of the CW laser light source 5.

[0036] The optical frequency of the CW laser light source 5 is controlled by the frequency control signal S CTL1 Thus, the CEO frequency f CEO The optical frequency of the CW laser light source 5 can be continuously changed by the frequency modulation width.

[0037] On the other hand, the RF frequency counter 21 of the CEO signal detector 4a detects the CEO signal S CEO frequency f CEO The digitizer 16 of the spectroscopic measurement unit 3 obtains the received light signal S obtained by the line sensor 14-2 based on the output of the RF frequency counter 21. sp and the reference signal S obtained by the line sensor 14-1. ref and CEO signal S CEOIt is synchronized with the camera and then captured and digitized.

[0038] The digitizer 16 converts the spectral data (received light signal S sp data or received light signal S sp is the reference signal S ref When the acquisition of the data (normalized by the intensity of the signal) is completed, the frequency modulation signal S output from the frequency modulation signal generator 19 is MOD1 In this way, by changing the output frequency of the frequency modulation signal generator 19 every time the acquisition of spectroscopic data is completed, the frequency of f n =f ceo +n×f rep Spectroscopic data can be acquired for each of the above modes. The control of the frequency modulation signal generator 19 by the digitizer 16 is the same in the following examples.

[0039] The measurement time in this embodiment is the modulation speed of the frequency modulation signal generator 19 or the data acquisition time by the line sensors 14-1, 14-2 and digitizer 16, enabling high-speed spectroscopy on the order of microseconds. Generally, the data acquisition time is several orders of magnitude faster than the frequency modulation speed, so the data acquisition time is the measurement time.

[0040] If the modulation speed of the frequency modulation signal generator 19 is approximately the same as the data acquisition time by the line sensors 14-1, 14-2 and the digitizer 16, it is necessary to synchronize the frequency modulation signal generator 19 and the digitizer 16 as shown by signal line 100 in Figure 3.

[0041] Thus, in this embodiment, precision spectroscopy can be easily performed with a single laser light source at a frequency resolution as high as that of conventional dual-comb spectroscopy.

[0042] In this embodiment, the CEO signal S CEO The optical frequency of the CW laser light source 5 is controlled by measuring the CEO frequency f CEOHowever, it is difficult to control the frequency near zero or at half the set frequency of the signal generator 7. To completely interpolate the mode spacing of the EO comb, two self-referencing interferometers must be prepared. One of the self-referencing interferometers is configured as a Mach-Zehnder interferometer, and a single-sideband modulator or an acousto-optic element is inserted in the optical path of this interferometer to generate the CEO signal S. CEO If the frequency of the EO comb mode is pseudo-shifted, the EO comb mode interval can be perfectly interpolated by the frequency modulation feedback circuit 20.

[0043] [Third Example] Next, a third embodiment of the present invention will be described. Fig. 4 is a diagram showing an example of the configuration of a single-comb spectrometer according to the third embodiment of the present invention. The single-comb spectrometer of this embodiment includes an EO comb generator 1a, a broadband light generator 2, a spectroscopic measurement unit 3, a CEO signal detector 4a, and a feedback circuit unit 4c. The feedback circuit unit 4c includes a frequency divider 18, a frequency modulation signal generator 19, and a frequency modulation feedback circuit 20c.

[0044] In the second embodiment, in order to change the optical frequency of the CW laser light source 5, a frequency control signal S CTL1 The injection current value of the CW laser light source 5 was controlled by the above.

[0045] In contrast, in this embodiment, an EO comb generator 1a is provided instead of the EO comb generator 1, and frequency-modulates the CW light output from the CW laser light source 5. The EO comb generator 1a is composed of the CW laser light source 5, an optical modulator 6, a signal generator 7, a dispersive medium 8, a modulator 22 (second modulator), a frequency-tuning signal generator 23, a frequency multiplier 24, and an RF amplifier 25.

[0046] The modulator 22 is an acousto-optical element or a single-sideband electro-optical modulator. The frequency varying signal generator 23 generates a frequency varying signal S MOD2 Output. The frequency multiplier 24 outputs a frequency variable signal S MOD2The frequency of the signal is multiplied by N. The RF amplifier 25 amplifies the output signal of the frequency multiplier 24.

[0047] The modulator 22, which is made up of an acousto-optical element, shifts the frequency of the CW light output from the CW laser light source 5 by the frequency of the output signal of the RF amplifier 25. In this embodiment, the frequency control signal S output from the frequency modulation feedback circuit 20c of the feedback circuit section 4c CTL2 is the frequency variable signal S MOD2 The frequency is 0 to f rep / N. In this embodiment, the frequency of the CW light output from the CW laser light source 5 is changed continuously within the range of 0 to f rep It is possible to repeat the frequency shift continuously within the range of .

[0048] When a single sideband electro-optic modulator 22 is used as the modulator 22, the frequency control signal S output from the frequency modulation feedback circuit 20c of the feedback circuit section 4c is CTL2 represents the frequency of the CW light output from the CW laser light source 5, from 0 to f rep This voltage signal is used to repeatedly shift the frequency continuously within the range of . The other configurations are the same as those in the second embodiment.

[0049] Although the second and third embodiments use the frequency divider 18, if a frequency modulation signal generator 19 capable of high-speed modulation over a wide bandwidth such as 25 GHz can be used, the frequency divider 18 is not necessary.

[0050] [Fourth Example] Next, a fourth embodiment of the present invention will be described. FIG. 5 is a diagram showing an example of the configuration of a single-comb spectrometer according to the fourth embodiment of the present invention. The single-comb spectrometer of this embodiment includes an EO comb generator 1, a broadband light generator 2, a spectroscopic measurement unit 3, a CEO signal detector 4a, and a feedback circuit unit 4d. In the second and third embodiments, the CEO signal S CEOis divided by N by the frequency divider 18 to down-convert the frequency, but in this embodiment, a multiplier is used to multiply the output frequency of the frequency modulation signal generator 19 by N in order to expand the modulation bandwidth of the frequency modulation signal generator 19.

[0051] The feedback circuit section 4d comprises a frequency modulation signal generator 19, a frequency modulation feedback circuit 20d, and a frequency multiplier 27. The frequency multiplier 27 multiplies the frequency modulation signal S output from the frequency modulation signal generator 19 by MOD1 The frequency is multiplied by N.

[0052] The frequency modulation feedback circuit 20d is a feedback circuit for modulating a frequency of the output signal of the frequency multiplier 27 and a CEO signal S CEO and a frequency control signal S for modulating the optical frequency of the CW laser light source 5 based on the comparison result. CTL1 The other configurations are the same as those in the second embodiment. In this way, the present embodiment can achieve the same effects as the second embodiment.

[0053] In this embodiment, the frequency multiplier 27 is applied to the second embodiment, but it may also be applied to the third embodiment. The configuration in this case is shown in FIG. The feedback circuit section 4 e comprises a frequency modulation signal generator 19 , a frequency modulation feedback circuit 20 e , and a frequency multiplier 27 .

[0054] The frequency modulation feedback circuit 20d is a feedback circuit for modulating a frequency of the output signal of the frequency multiplier 27 and a CEO signal S CEO Based on this, the frequency variable signal S MOD2 The frequency is 0 to f rep / N CTL2 As explained in the third embodiment, when a single sideband electro-optic modulator 22 is used as the modulator 22, the frequency control signal S CTL2 represents the frequency of the CW light output from the CW laser light source 5, from 0 to f rep This voltage signal is used to continuously shift the frequency within the range of

[0055] [Fifth Example] Next, a fifth embodiment of the present invention will be described. Fig. 7 shows an example of the configuration of a single-comb spectrometer according to the fifth embodiment of the present invention. The single-comb spectrometer of this embodiment includes an EO comb generator 1, a broadband light generator 2, a spectroscopic measurement unit 3, and a CEO signal detector 4f. The CEO signal detection unit 4f comprises a self-referencing interferometer 17, an RF frequency counter 21, a data accumulation device 26, and a setting unit .

[0056] In the second embodiment, the CEO signal S CEO On the other hand, in this embodiment, the CW laser light source 5 is controlled to have a CEO frequency f CEO It operates with a free rung where the position is not fixed.

[0057] In this example, before the operation of the single-comb spectrometer, the CEO frequency f CEO and the injection current value of the CW laser light source 5. At this time, the frequency of the CW laser light source 5 is the CEO frequency f CEO This can be calculated by a data collection device 26 that collects the results of the RF frequency counter 21 that measures the frequency.

[0058] The setting unit 28 of the CEO signal detection unit 4f detects the CEO frequency f stored in the data collection device 26. CEO and the injection current value of the CW laser light source 5, the optical frequency of the CW laser light source 5 is f rep The injection current value is set for the CW laser light source 5 so that the modulation width is continuously changed repeatedly. With such settings, the driver (not shown) of the CW laser light source 5 automatically and repeatedly changes the injection current value, so that the CW laser light source 5 operates in a free run.

[0059] As in the second embodiment, the digitizer 16 of the spectroscopic measurement unit 3 converts the received light signal S obtained by the line sensor 14-2 into sp and the reference signal S obtained by the line sensor 14-1.ref and CEO signal S CEO It is synchronized with the camera and then captured and digitized.

[0060] The data collection device 26 also receives the CEO frequency f CEO Based on the measurement results, the CEO frequency f CEO Output the data. The digitizer 16 converts the spectral data (received light signal S sp data or received light signal S sp is the reference signal S ref (data normalized by the intensity of the CEO frequency f CEO Data and repetition frequency f rep Labeling is performed by adding the data.

[0061] As described above, in this embodiment, the CEO frequency f CEO By labeling the data, the measurement conditions of the spectroscopic data can be identified. The labeling configuration of this embodiment may be applied to the first to fourth embodiments.

[0062] Although the present invention has been specifically described based on the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment and various modifications can be made without departing from the spirit and scope of the present invention. For example, if a high signal-to-noise ratio is not required, spectroscopic measurement can be performed using a single optical path without branching the light using the optical demultiplexer 12. [Industrial Applicability]

[0063] The present invention can be applied to techniques for obtaining precise spectroscopic data. [Explanation of symbols]

[0064] 1,1a...EO comb generation unit, 2...broadband light generation unit, 3...spectroscopic measurement unit, 4a,4f...CEO signal detection unit, 4b,4c,4d,4e...feedback circuit unit, 5...CW laser light source, 6...optical modulation unit, 7...signal generator, 8...dispersion medium, 9...optical amplifier, 10...dispersion compensator, 11...highly nonlinear medium, 12...optical splitter, 13-1,13-2...diffraction grating, 14-1,14-2...line sensor, 15...spectroscopic sample, 16...digitizer, 17...self-referencing interferometer, 18...frequency divider, 19...frequency modulation signal generator, 20,20c,20d,20e...feedback circuit for frequency modulation, 21...RF frequency counter, 22...modulator, 23...frequency variable signal generator, 24,27...frequency multiplier, 25...RF amplifier, 26...data accumulation device, 28...setting unit.

Claims

1. a continuous wave laser light source; a first modulator configured to phase-modulate the laser light from the continuous wave laser light source at a predetermined repetition rate to generate an electro-optic modulation comb; a detector configured to detect a carrier-envelope offset frequency of the electro-optic modulation comb; a feedback circuit configured to modulate the optical frequency of the continuous wave laser light source based on the carrier envelope offset frequency; a spectroscopic measurement unit configured to obtain spectroscopic data from an observation result of the electro-optic modulation comb transmitted through a sample; a digitizer configured to acquire the spectroscopic data synchronously with a carrier envelope offset signal indicative of the carrier envelope offset frequency; a data collection device configured to output data of the carrier envelope offset frequency; The single-comb spectroscopic device is characterized in that the digitizer performs labeling by adding data of the carrier envelope offset frequency to the spectroscopic data.

2. 2. The single-comb spectroscopic device according to claim 1, The single-comb spectrometer is characterized in that the feedback circuit section modulates the optical frequency of the continuous-wave laser light source by changing the injection current value of the continuous-wave laser light source.

3. 2. The single-comb spectroscopic device according to claim 1, a second modulator, which is a single-sideband electro-optic modulator or an acousto-optical element, provided downstream of the continuous wave laser light source; The single-comb spectrometer is characterized in that the feedback circuit section modulates the optical frequency of the continuous wave laser light source by controlling the second modulator.

4. 4. The single-comb spectroscopic device according to claim 1, The single comb spectrometer is characterized in that the feedback circuit section modulates the optical frequency of the continuous wave laser light source so that the carrier envelope offset frequency changes continuously by the repetition frequency.

5. 5. The single-comb spectroscopic device according to claim 1, The feedback circuit unit includes: a frequency modulation signal generator configured to output a frequency modulation signal; a frequency divider configured to divide the carrier envelope offset signal; and a frequency modulation feedback circuit configured to output a frequency control signal for modulating the optical frequency of the continuous wave laser light source based on the result of comparing the frequency modulation signal with the output signal of the frequency divider.

6. a continuous wave laser light source configured to continuously change its optical frequency; a modulator configured to phase-modulate the laser light from the continuous wave laser light source at a predetermined repetition rate to generate an electro-optic modulation comb; a detector configured to detect a carrier-envelope offset frequency of the electro-optic modulation comb; a spectroscopic measurement unit configured to obtain spectroscopic data from an observation result of the electro-optic modulation comb transmitted through a sample; a digitizer configured to acquire the spectroscopic data synchronously with a carrier envelope offset signal indicative of the carrier envelope offset frequency; a data collection device configured to output data of the carrier envelope offset frequency; The single-comb spectroscopic device is characterized in that the digitizer performs labeling by adding data of the carrier envelope offset frequency to the spectroscopic data.

7. 7. The single-comb spectroscopic device according to claim 6, The single-comb spectroscopic device is characterized in that the optical frequency of the continuous wave laser light source changes continuously by the repetition frequency.

8. 8. The single-comb spectrometer according to claim 1, a dispersion medium configured to convert the electro-optic modulation comb into an optical pulse train by applying wavelength dispersion to the electro-optic modulation comb; a dispersion compensator configured to compress the pulse width of the optical pulse train to shorten the pulses; a nonlinear medium configured to expand the bandwidth of the optical pulse train output from the dispersion compensator, The spectroscopic measurement unit is a single-comb spectroscopic device characterized in that light whose bandwidth has been expanded by the nonlinear medium is incident on the sample.

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