JP7731097B2 - Single-comb spectrometer - Google Patents

Description

The present invention relates to a single-comb spectroscopy device that performs precision spectroscopy using an electro-optic modulation comb.

Conventional spectrometers can be broadly divided into two types: dispersive and Fourier transform. 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.

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

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 larger, allowing for higher frequency resolution (see non-patent document 1).

As such, dual-comb spectroscopy is a high-speed, high-resolution spectroscopy method, but it requires highly advanced technology, as the repetition rate and phase of two ML lasers must be synchronized with high precision using a complex control mechanism. For this reason, dual-comb spectroscopy has only been performed at a few cutting-edge ML laser research institutes, and has been a barrier to widespread adoption of high-speed, precision 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.

IAN CODDINGTON, NATHAN NEWBURY, AND WILLIAM SWANN, “Dual-comb spectroscopy”, Vol.3, No.4, April 2016, Optica

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.

The single-comb spectroscopic device of the present invention comprises a continuous-wave laser light source, a first modulator configured to generate an electro-optic modulation comb by phase-modulating laser light from the continuous-wave laser light source at a predetermined repetition rate, 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.

In addition, 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 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 is characterized in that it 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.

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.

Furthermore, one example configuration of the single-comb spectroscopic device of the present invention further includes a dispersive 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 characterized in that the light whose bandwidth has been expanded by the nonlinear medium is incident on the sample.

Because electro-optic modulation comb-based single-comb spectroscopy allows for highly accurate control of the optical frequency of the electro-optic modulation comb's seed light source, this invention makes it possible to easily perform 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 performed in an order of magnitude or more shorter than conventional dual-comb spectroscopy.

FIG. 1 is an explanatory diagram showing an electro-optic modulation comb. FIG. 2 is a schematic diagram showing the basic configuration of a single-comb spectrometer according to a first embodiment of the present invention. FIG. 3 is a diagram showing an example of the configuration of a single-comb spectrometer according to a second embodiment of the present invention. FIG. 4 is a diagram showing an example of the configuration of a single-comb spectrometer according to a third embodiment of the present invention. FIG. 5 is a diagram showing an example of the configuration of a single-comb spectrometer according to a fourth embodiment of the present invention. FIG. 6 is a diagram showing another example of the configuration of a single-comb spectrometer according to the fourth embodiment of the present invention. FIG. 7 is a diagram showing an example of the configuration of a single-comb spectrometer according to a fifth embodiment of the present invention.

[Principles of the Invention]
To overcome the problems of the dual-comb spectroscopy, 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.

FIG. 1 is an explanatory diagram showing an EO comb. As shown in FIG. 1, an EO comb is a collection of many modes arranged in a comb-like pattern on the frequency axis at a repetition frequency f _rep that is equally spaced. 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 of each mode of the EO comb can be expressed as f _n = f _ceo + n × f _rep (n is an integer), where f _CEO is the CEO frequency.

This invention combines broadband, high resolution, high speed, and simplicity, and does not require advanced phase synchronization of the laser as in conventional methods. This allows for easy operation by anyone other than laser experts, and realizes a spectroscopic device that can be used in field environments, enabling high-resolution, high-speed real-time measurements.

[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.

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 effect, cross-phase modulation effect, etc.). This broadband light is used by the spectroscopic measurement unit 3 to acquire spectroscopic data.

The mode spacing of an EO comb can be set arbitrarily using a signal generator, and the bandwidth can be broadened by widening the mode spacing. However, this does not provide sufficient resolution for precision spectroscopy such as molecular spectroscopy. Therefore, it is necessary to interpolate the EO comb mode spacing.

In this embodiment, the broadband light output from the broadband light generation unit 2 is input to the CEO signal detection unit 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 generation unit 1 can be measured with the accuracy of an RF frequency counter, making precise spectroscopy possible with just one EO comb. By high-speed frequency modulating the CW laser light source using the CEO frequency and feedback circuit unit 4b, the EO comb mode spacing can be interpolated, enabling wideband and high-speed single comb spectroscopy.

[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.

The EO comb generator 1 includes a CW laser light source 5 made of a semiconductor laser, an optical modulator 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 .

The spectroscopic measurement unit 3 comprises an optical splitter 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 comprises a self-referencing interferometer 17 and an RF frequency counter 21 .
The feedback circuit section 4 b comprises a frequency divider 18 , a frequency modulation signal generator 19 , and a frequency modulation feedback circuit 20 .

The EO comb generator 1 uses a CW laser light source 5 as the seed light source for the EO comb. The CW laser light source 5 generates CW light at 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.

The optical modulation unit 6 includes an intensity modulator and a phase modulator. The intensity modulator and the phase modulator are driven by a sinusoidal microwave signal S1 having a frequency f _rep = 25 GHz, for example, from a signal generator 7. As a result, the optical modulation unit 6 phase-modulates the CW light from the CW laser light source 5 at the repetition frequency f _rep , and generates an EO comb having a frequency mode spacing of the repetition frequency f _rep .

A dispersive medium 8 such as a single-mode fiber applies chromatic dispersion to the EO comb output from the optical modulator 6, thereby converting the EO comb into an optical pulse train with a repetition frequency of f _rep . The optical pulse train transmitted through the dispersive medium 8 enters the broadband light generator 2.

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

The highly nonlinear medium 11 expands the bandwidth of the high-power short optical pulse train. The broadband light whose bandwidth has been expanded by the highly nonlinear medium 11 is incident on the spectroscopic measurement unit 3 and the CEO signal detection unit 4a.

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 different directions for each wavelength. The line sensor 14-1 receives the light split by the diffraction grating 13-1 and converts it into an electrical signal (reference signal) S _ref .

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 that has passed through the spectroscopic sample 15 into different directions for each wavelength. The line sensor 14-2 receives the light split by the diffraction grating 13-2 and converts it into an electrical signal (spectroscopic signal) _Ssp .

The digitizer 16 can acquire the absorption spectrum of the spectroscopic sample 15 with a high signal-to-noise ratio by normalizing the received light signal S _sp obtained by the line sensor 14-2 with the intensity of the reference signal S _ref obtained by the line sensor 14-1.

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

In this embodiment, the CEO frequency f _CEO is changed by the repetition frequency f _rep of the EO comb. For example, if the frequency of the signal generator 7 is set to 25 GHz (= f _rep ), the mode spacing of the EO comb is 25 GHz. Therefore, by frequency-modulating the CEO frequency f _CEO by 25 GHz, the frequency mode spacing of the EO comb can be interpolated to perform precise spectroscopy. However, since there is no signal generator capable of high-speed modulation of a wide bandwidth such as 25 GHz, the CEO signal S _CEO is frequency-downconverted by dividing it by N (N is an integer greater than or equal to 2) using the frequency divider 18.

The frequency modulation signal generator 19 of the feedback circuit 4b outputs a frequency modulation signal S _MOD1 that repeats continuous frequency changes with a modulation width of f _rep /N, using the reference value of f _CEO as the reference frequency. Note that the frequency of the frequency modulation signal S _MOD1 changes under control of the digitizer 16, as will be described later.

The frequency modulation feedback circuit 20 of the feedback circuit section 4b compares the phase of the frequency modulation signal S _MOD1 with the output signal of the frequency divider 18, and outputs a frequency control signal S _CTL1 based on the comparison result. The frequency control signal S _CTL1 in this embodiment is a signal for modulating the optical frequency of the CW laser light source 5 with a modulation width of f _rep , and more specifically, is a signal for changing the injection current value of the CW laser light source 5.

The optical frequency of the CW laser light source 5 changes in response to the frequency control signal S _CTL1 . In this way, the optical frequency of the CW laser light source 5 can be continuously changed by the frequency modulation width of the CEO frequency f _CEO .

Meanwhile, the RF frequency counter 21 of the CEO signal detection unit 4a acquires the frequency f _CEO of the CEO signal S _CEO . Based on the output of the RF frequency counter 21, the digitizer 16 of the spectroscopic measurement unit 3 captures the light reception signal S _sp obtained by the line sensor 14-2 and the reference signal S _ref obtained by the line sensor 14-1 in synchronization with the CEO signal S _CEO and digitizes them.

When the digitizer 16 finishes acquiring spectroscopic data (data of the received light signal _Ssp , or data obtained by normalizing the received light signal _Ssp with the intensity of the reference signal _Sref ), it changes the frequency of the frequency modulation signal _SMOD1 output from the frequency modulation signal generator 19. In this way, by changing the output frequency of the frequency modulation signal generator 19 each time acquisition of spectroscopic data is completed, spectroscopic data can be acquired for each mode of _fn = _fceo + _nxfrep . The control of the frequency modulation signal generator 19 by the digitizer 16 is the same in the following embodiments.

In this embodiment, the measurement time is the modulation speed of the frequency modulation signal generator 19, or the data acquisition time using 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.

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

In this way, in this embodiment, precision spectroscopy can be easily performed with a single laser light source at a frequency resolution comparable to that of conventional dual-comb spectroscopy.

In this embodiment, the CEO signal S _CEO is measured to control the optical frequency of the CW laser light source 5, but control is difficult when the CEO frequency f _CEO is near zero or at half the frequency set by the signal generator 7. To completely interpolate the EO comb mode spacing, two self-referencing interferometers are required. If 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 into the optical path of this interferometer to artificially frequency-shift the CEO signal S _CEO , the EO comb mode spacing can be completely interpolated by the frequency modulation feedback circuit 20.

[Third Example]
Next, a third embodiment of the present invention will be described. Fig. 4 shows 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 4c. The feedback circuit 4c includes a frequency divider 18, a frequency modulation signal generator 19, and a frequency modulation feedback circuit 20c.

In the second embodiment, in order to change the optical frequency of the CW laser light source 5, the injection current value of the CW laser light source 5 is controlled by the frequency control signal _SCTL1 from the frequency modulation feedback circuit 20.

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 dispersion medium 8, a modulator 22 (second modulator), a frequency-variable signal generator 23, a frequency multiplier 24, and an RF amplifier 25.

The modulator 22 is an acousto-optical element or a single-sideband electro-optical modulator. The frequency varying signal generator 23 outputs a frequency varying signal S _MOD2 .
The frequency multiplier 24 multiplies the frequency of the frequency varying signal S _MOD2 by N. The RF amplifier 25 amplifies the output signal of the frequency multiplier 24 .

The modulator 22, which is made up of an acousto-optic element, shifts the frequency of the CW light output from the CW laser light source 5 by the frequency of the output signal from the RF amplifier 25. In this embodiment, the frequency control signal S _CTL2 output from the frequency modulation feedback circuit 20 c of the feedback circuit section 4 c is a signal for repeatedly changing the frequency of the frequency varying signal S _MOD2 continuously within the range of 0 to f _rep /N. As a result, in this embodiment, the frequency of the CW light output from the CW laser light source 5 can be repeatedly shifted continuously within the range of 0 to f _rep .

When a single-sideband electro-optic modulator 22 is used as the modulator 22, the frequency control signal _SCTL2 output from the frequency modulation feedback circuit 20c of the feedback circuit section 4c becomes a voltage signal for repeatedly shifting the frequency of the CW light output from the CW laser light source 5 continuously within the range of 0 to _frep .
The other configurations are the same as those of the second embodiment.

In the second and third embodiments, a frequency divider 18 is used, but 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.

[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 4d. In the second and third embodiments, the CEO signal S _CEO is divided by N using a frequency divider 18 to down-convert the frequency. However, 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.

The feedback circuit section 4 d comprises a frequency modulation signal generator 19 , a frequency modulation feedback circuit 20 d , and a frequency multiplier 27 .
The frequency multiplier 27 multiplies the frequency of the frequency modulation signal S _MOD1 output from the frequency modulation signal generator 19 by N times.

The frequency modulation feedback circuit 20d compares the phase of the output signal of the frequency multiplier 27 with the CEO signal S _CEO and, based on the comparison result, outputs a frequency control signal S _CTL1 for modulating the optical frequency of the CW laser light source 5. The other configurations are the same as those of the second embodiment.
In this way, the present embodiment can achieve the same effects as the second embodiment.

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 .

The frequency modulation feedback circuit 20d outputs a frequency control signal S CTL2 for continuously changing the frequency of the frequency varying signal S _MOD2 in the range of 0 to f _rep /N based on the output signal of the frequency multiplier 27 and the _CEO signal S _CEO . As described in the third embodiment, when a single-sideband electro-optic modulator 22 is used as the modulator 22, the frequency control signal S _CTL2 becomes a voltage signal for continuously frequency-shifting the frequency of the CW light output from the CW laser light source 5 in the range of 0 to f _rep .

[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 .

In the second embodiment, the optical frequency of the CW laser light source 5 is changed based on the CEO signal S _CEO using the frequency modulation feedback circuit 20. In contrast, in this embodiment, the CW laser light source 5 is operated in a free run where the CEO frequency f _CEO is not determined.

In this example, before operating the single-comb spectrometer, the relationship between the CEO frequency f _CEO and the injection current value of the CW laser light source 5 is measured. At this time, the frequency of the CW laser light source 5 can be calculated by a data collection device 26 that collects the results of an RF frequency counter 21 that measures the CEO frequency f _CEO .

Based on the relationship between the CEO frequency f _CEO stored in the data accumulation device 26 and the injection current value of the CW laser light source 5, the setting unit 28 of the CEO signal detection unit 4f sets the injection current value for the CW laser light source 5 so that the optical frequency of the CW laser light source 5 repeatedly changes continuously with a modulation width of _f rep.
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.

As in the second embodiment, the digitizer 16 of the spectroscopic measurement unit 3 takes in the light reception signal S _sp obtained by the line sensor 14-2 and the reference signal S _ref obtained by the line sensor 14-1 in synchronization with the CEO signal S _CEO and digitizes them.

Furthermore, the data accumulator 26 outputs data on the CEO frequency f _CEO based on the measurement result of the CEO frequency f _CEO .
The digitizer 16 performs labeling by adding data on the CEO frequency f _CEO and data on the repetition frequency f _rep to the spectroscopic data (data on the received light signal S _sp or data on the received light signal S _sp normalized by the intensity of _the reference signal S ref).

As described above, in this embodiment, by performing labeling to add data on the CEO frequency f _CEO to the spectroscopic 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.

The present invention has been specifically described above based on the above-mentioned embodiment, but the present invention is not limited to the above-mentioned embodiment and various modifications are possible without departing from the spirit of the 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 splitter 12.

This invention can be applied to technologies for obtaining precise spectroscopic data.

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 demultiplexer, 13-1, 13-2...diffraction grating, 14-1, 14-2...light Sensor, 15...spectroscopic sample, 16...digitizer, 17...self-referencing interferometer, 18...frequency divider, 19...frequency modulation signal generator, 20, 20c, 20d, 20e...frequency modulation feedback circuit, 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 (8)

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. 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. 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. 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. 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. 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. 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. 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.