JP5475341B2 - Multi-wavelength simultaneous absorption spectroscopy apparatus and multi-wavelength simultaneous absorption spectroscopy method - Google Patents

Description

  The present invention relates to a multi-wavelength simultaneous absorption spectrometer having high sensitivity and high frequency detection accuracy.

  In recent years, methods for stabilizing the frequency of an optical frequency comb have been proposed and realized, and in particular, an optical frequency comb light source in which the wavelength of the optical frequency comb is stabilized by locking a carrier envelope offset (hereinafter referred to as “CEO”). Has been proposed (see Patent Document 1, Non-Patent Documents 1 to 6). These optical frequency comb light sources with accurately determined wavelengths for each mode of optical frequency combs are applied not only to high-precision frequency standards and related basic physics, but also to fields such as communications, precision measurement, and quantum information communications. Is expected to be a technology.

  In the field of precision measurement, a highly sensitive measurement technique based on absorption spectroscopy with ultra-high resolution using this CEO-locked optical frequency comb light source has been proposed (Non-patent Documents 7 and 8). This technique is a measurement technique using absorption spectroscopy in which an optical frequency comb light source is applied to capital ring-down spectroscopy (hereinafter referred to as “CRDS method”). According to the CRDS method using this optical frequency comb light source, the obtained data is characterized in that it can be acquired with high sensitivity and has high accuracy on the frequency axis.

This CRDS method is a high-sensitivity absorption spectroscopy that measures the absorption of molecules in a cavity by observing the intensity attenuation of light confined in the cavity composed of two high-reflectance mirrors. It is. A configuration example of this cavity is shown in FIG.
When pulse light is incident from one of the cavities in which two high-reflectivity mirrors as shown in FIG. 6 face each other, the light entering the cavity gradually attenuates its intensity between the two mirrors. Repeat round trip in the cavity. At this time, when the light is reflected by the mirror, a part of the light leaks out of the mirror. The CRDS method is a method for realizing a highly sensitive absorption spectroscopy measurement by measuring the leaked light waveform.

The CRDS method will be described in detail with specific mathematical expressions.
Here, when there is no substance that absorbs light in the cavity, that is, in a vacuum, the intensity waveform of light leaking when reflected from the mirror (hereinafter referred to as “leakage light”) is:
I (t) = I ₀ exp (−t / τ ₀ )
It is expressed. Here, I ₀ is the initial amplitude of light, and τ ₀ is the decay lifetime of light confined in the cavity (hereinafter referred to as “ring-down time”).
Next, if there is even a slight amount of light absorbing material in the cavity, the intensity waveform of the leaked light is
I (t) = I ₀ exp {− (1 / τ ₀ + σ * n * c) t}
It is expressed. Here, σ is the absorption cross section (or scattering cross section) of the light absorbing material present in the cavity, n is the number density of the absorbing material, and c is the speed of light .
From these equations, the difference between the reciprocal of the ring-down time when the absorbing material is present and the reciprocal of the ring-down time in vacuum, ie, (σ * n * c), is the concentration of the light-absorbed material in the cavity. Proportional. Therefore, quantification of the concentration of the measurement object can be realized.

JP 2009-116242 A

D.J.Jones, et al., "Carrier-Envelope Phase Control of Femtosecond Mode-Locked Lasers and Direct Optical Frequency Synthesis", Science, Vol.288, pp.635-639, 2000. R. Holzwarth, et al., "Optical Frequency Synthesizer for Precision Spectroscopy", Phys. Rev. Lett., Vol.85, No.11, pp.2264-2267, 2000. K. Sugiyama, et al., "Frequency Control of a Chirped-Mirror-Dispersion-Controlled Mode-Locked Ti: Al2O3 Laser for Comparison between Microwave and Optical Frequencies", Proceedings of SPIE, Vol.4269, pp.95-104, 2001 T.R.Schibli, et al., "Frequency metrology with a turnkey all-fiber system", Optics Letters, Vol.29, No.21, pp.2467-2469, 2004. T.M.Foritier, et al., "Octave-spanning Ti: sapphire laser with a repetition rate> 1 GHz for optical frequency measurements and comparisons", Optics Letters, Vol.31, No.7, pp.1011-1013, 2006. I. Hartl, et al., "Integrated self-referenced frequency-comb laser based on a combination of fiber and waveguide technology", Optics Express, Vol. 13, No. 17, pp. 6490-6496, 2005. M.J.Thorpe, et al., "Cavity-enhanced direct frequency comb spectroscopy", Applied Physics B-Lasers and Optics, B91, pp.397-414, 2008. M.J.Thorpe, et al., "Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis", Optics Express, Vol.16, No.4, pp.2387-2397, 2008. A. Bartels, et al., "Spectrally resolved optical frequency comb from a self-referenced 5GHz femtosecond laser", Optics Letters, Vol.32, No.17, pp.2553-2555, 2007.

However, in the CRDS method using the conventional CEO-locked optical frequency comb light source disclosed in Non-Patent Document 7 or 8, the ring-down time and the attenuation coefficient (light absorption cross section or scattering cross section of the measurement target substance) , Number density in the cavity), the decay lifetime of light incident in the cavity is determined. For this reason, there is a problem that the measurement accuracy by the absorption spectroscopy is deteriorated due to the attenuation coefficient inherent to the substance. That is, as the attenuation coefficient inherent to the substance increases, the attenuation lifetime of the light in the cavity is shortened, making it difficult to observe the leaked light waveform and degrading the measurement accuracy.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a multi-wavelength simultaneous absorption spectroscopic device in which the measurement accuracy is improved by reducing the influence of the attenuation coefficient inherent to a substance.

  To achieve the above object, the present invention provides a carrier envelope offset (CEO) -locked optical frequency comb light source unit, and a branching unit that branches laser light output from the optical frequency comb light source into two laser beams. A probe light extraction unit for extracting one of the laser beams branched by the branching unit as a probe light and entering the cavity where the measurement object is placed, and extracting an output waveform of the probe light; and the branching unit Of the branched laser light, the other laser light is used as a reference light, the frequency is shifted, and the reference light whose frequency is shifted is incident on the vacuum cavity with the same configuration as the cavity in which the measurement object is installed. A reference light extraction unit that extracts an output waveform of light, and extracted by the probe light extraction unit An interference signal deriving unit for causing interference light to interfere with the reference light extracted by the reference light extracting unit, and an interference signal for deriving the light intensity of each mode of the optical frequency comb of the interference signal measured by the interference signal deriving unit And an adjustment unit.

  Further, the reference light extraction unit of the multi-wavelength simultaneous absorption spectroscopic device of the present invention performs a frequency shift of each frequency of the optical frequency comb in the reference light by a predetermined frequency by phase-modulating the reference light by a predetermined frequency. It is good also as a structure provided with a shifter part and the cavity part which has the same cavity ring time as the cavity of the said probe light extraction part.

  Further, the interference signal deriving unit of the multi-wavelength simultaneous absorption spectroscopic device of the present invention first combines the probe light output by the probe light extraction unit and the reference light output by the reference light extraction unit, The signal may be re-branched into the second interference signal and the second interference signal.

  Further, the interference signal adjusting unit of the multi-wavelength simultaneous absorption spectroscopic device of the present invention includes an interference signal spectroscopic unit that splits the first and second interference signals for each mode of the optical frequency comb, and the interference signal spectroscopic unit. It is good also as a structure provided with the interference signal intensity | strength detection part which detects the difference of the said 1st and 2nd interference signal disperse | distributed for every mode of the optical frequency comb.

  According to the present invention, a CEO-locked optical frequency comb light source is bifurcated into a probe light and a reference light, and frequency-shifted with the probe light that is subjected to absorption spectroscopy by the CRDS method on the object to be measured. By interfering with the output reference light and deriving the difference between the branched interference signals, the attenuation time of the measurement object can be extended, and a material with a short attenuation life that has been difficult to measure with the conventional CRDS method In addition, it enables precise spectroscopic measurement by multi-wavelength simultaneous absorption spectroscopy using a CEO-locked optical frequency comb light source.

1 is a block diagram showing a configuration of a multi-wavelength simultaneous absorption spectrometer according to a first embodiment of the present invention. It is a figure which shows the optical intensity of the interference signal derived | led-out by the multiwavelength simultaneous absorption spectroscopy apparatus concerning the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the multiwavelength simultaneous absorption spectroscopy apparatus concerning the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the computer which improves the measurement sensitivity in the multiwavelength simultaneous absorption spectroscopy apparatus concerning the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the multiwavelength simultaneous absorption spectroscopy apparatus concerning the 3rd Embodiment of this invention. It is a figure which shows an example of a structure of the optical cavity used by cavity ring down spectroscopy. It is a figure which shows an example of the measurement waveform of the leak light from an optical cavity.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A multi-wavelength simultaneous absorption spectrometer according to an embodiment of the present invention described below is an example of an embodiment of the present invention, and a specific configuration is not limited to this embodiment. In other words, design changes within the scope of the present invention are included in the present invention.

[First Embodiment]
The multi-wavelength simultaneous absorption spectrometer according to the first embodiment of the present invention realizes precise spectroscopic measurement by cavity ring-down spectroscopy (CRDS method) using an optical frequency comb stabilized light source.
As shown in FIG. 1, the multi-wavelength simultaneous absorption spectrometer 10 according to the present embodiment includes an optical frequency comb light source unit 110, a branching unit 120, a probe light extraction unit 130, a reference light extraction unit 140, an interference The signal deriving unit 150 and the interference signal adjusting unit 160 are configured.

The optical frequency comb light source unit 110 is an optical frequency comb light source in which the repetition frequency of the passive mode-locked laser is equal to or higher than GHz and carrier envelope offset (CEO) is locked.
For example, it is desirable to use a CEO-locked optical frequency comb stabilized light source that generates a pulse train by applying phase modulation and wavelength dispersion to a CW (continuous light) light source (see Patent Document 1).

  The branching unit 120 is a beam splitter that branches the laser beam output from the optical frequency comb light source unit 110 into two laser beams. For example, a beam splitter that branches a laser beam is realized by using an optical coupler.

The probe light extraction unit 130 enters one of the laser beams branched by the branching unit 120 as the probe light and enters the optical cavity 131 where the measurement target is placed, and the output of the probe light from the optical cavity 131 A waveform, that is, a waveform of light leaked from the optical cavity 131 is extracted.
The reference light extraction unit 140 shifts the frequency of the other laser light of the laser light branched by the branching unit 120 by the frequency shifter 141, and uses the frequency-shifted laser light as a reference light to the optical cavity of the probe light extraction unit 130. The light beam enters the optical cavity 141 having the same configuration as 131 and is in a vacuum state, and the output waveform of the reference light (the waveform of the leakage light of the reference light) is extracted.

  The interference signal deriving unit 150 combines the probe light output from the optical cavity 131 extracted by the probe light extraction unit 130 and the reference light output from the optical cavity 141 extracted by the reference light extraction unit 140. Then, the combined interference signal is branched again into the first interference signal and the second interference signal.

The interference signal adjustment unit 160 adjusts the signal-to-noise ratio (SNR) of the interference signal from the first interference signal and the second interference signal derived by the interference signal deriving unit 150, and the light intensity of the interference signal Is derived.
The interference signal adjustment unit 160 includes a light intensity adjustment unit 161, an interference signal spectroscopic unit 162, and an interference signal intensity detection unit 163.

The light intensity adjustment unit 161 adjusts the light intensity so that the light intensity ratio between the first interference signal and the second interference signal derived by the interference signal deriving unit 150 becomes a predetermined value.
The interference signal spectroscopic unit 162 separates the first and second interference signals whose light intensity has been adjusted by the light intensity adjusting unit 161 for each mode of the optical frequency comb.
The interference signal intensity detecting unit 163 detects the first and second interference signals separated by the interference signal spectroscopic unit 162 for each mode of the optical frequency comb and detects the electrical signal for each same mode of the optical frequency comb. Digitize the signal difference.

  The multi-wavelength simultaneous absorption spectroscopic apparatus 10 according to the present embodiment is configured by installing a computer program in a computer having a CPU (Central Processing Unit), a memory, and an interface so that the above-described multi-wavelength simultaneous absorption spectroscopic apparatus 10 can be used. Hardware resources of a computer (not shown) mounted on the absorption spectrometer 10 and the computer program (software) are realized in cooperation.

  Next, an interference signal derived based on the waveform of leakage light from the optical cavity 131 extracted by the probe light extraction unit 130 and the waveform of leakage light from the optical cavity 141 extracted by the reference light extraction unit 140 is described. Simultaneously, the operation of the multi-wavelength simultaneous absorption spectrometer according to this embodiment will be described.

The optical cavities 131 and 141 have the same configuration. For example, a high reflectivity mirror (reflectance 99.9%) as shown in FIG. At this time, a sample (gas, solid, or the like) that is an object to be measured is placed inside the optical cavity 131, and the inside of the optical cavity 141 is in a vacuum state.
When the laser light output from the optical frequency comb light source unit 110 enters each optical cavity, the probe light extraction unit 130 and the reference light extraction unit 140 observe the leakage light from the optical cavity, and the respective waveforms are observed. Extract. These waveforms are represented by Expression (1) and Expression (2).
That is, the waveform of the leaked light from the optical cavity 131 extracted by the probe light extraction unit 130 is expressed by the following equation (1).

_{E 1 exp {- (1/2)} (1 / τ 0 + σ * n * c) t} sin (2πf s t + φ s) formula (1)
Here, f _s indicates the frequency of the probe light, and φ _s indicates the initial phase.

  On the other hand, the waveform of the leakage light from the optical cavity 141 extracted by the reference light extraction unit 140 is expressed by the following equation (2).

E ₂ exp (−t / 2τ ₀ ) sin (2πf _r t + φ _r ) Equation (2)
Here, f _r represents the frequency of the reference light, and φ _r represents the initial phase.

Further, since the frequency of the reference light is shifted by the frequency shifter 141, the frequency f _n of the Nth optical frequency comb of the reference light is f _n = N * f _rep + f ₀ ± f _b (f _rep is the repetition frequency) , F _b are expressed as frequency shift amount).

The interference signal deriving unit 150 multiplexes the respective leaked light expressed by the equations (1) and (2). When the two leaked lights are combined, the interference signal derivation 150 generates a phase difference of π / 2 in the two leaked lights. After the two leaked lights are combined, the interference signal deriving unit 150 branches the combined leaked light into two again, and outputs the first interference signal and the second interference signal.
The laser pulses branched again by the interference signal deriving unit 150, that is, the first interference signal and the second interference signal are expressed by the following equations (3) and (4), respectively.

_{E 1 exp {- (1/2)} (1 / τ 0 + σ * n * c) t} sin (2πf s t + φ s)
+ E ₂ exp (−t / 2τ ₀ ) sin (2πf _r t + φ _r + π / 2) Equation (3)
_{E 1 exp {- (1/2)} (1 / τ 0 + σ * n * c) t} sin (2πf s t + φ s + π / 2)
+ E ₂ exp (−t / 2τ ₀ ) sin (2πf _r t + φ _r ) (4)

Here, when the leakage lights represented by the expressions (1) and (2) are combined, a phase difference of π / 2 is given between the two leakage lights.
Further, the first interference signal represented by the expression (3) is obtained by causing the leakage light represented by the expression (1) to interfere with the leakage light represented by the expression (1). It can be considered that the second interference signal represented is obtained by causing the leakage light represented by the equation (1) to interfere with the leakage light represented by the equation (2).

  In order to set the branching ratio between the first interference signal and the second interference signal output by the interference signal deriving unit 150 to a predetermined value, the light intensity adjusting unit 161 of the interference signal adjusting unit 160 includes first and second interference signals. The light intensity of the interference signal is adjusted. Since the branching ratio between the first interference signal and the second interference signal at this time is preferably 1: 1, the light intensity adjusting unit 161 sets the light of each interference signal so that the branching ratio is 1: 1. Adjust the strength. For example, the light intensity may be automatically adjusted using a neutral density filter or the like.

The first and second interference signals whose light intensities are adjusted are split by the interference signal spectroscopic unit 162 for each mode of the optical frequency comb. For example, an arrayed waveguide diffraction grating or the like, which is an optical element for optical frequency comb mode separation, is used to separate each optical frequency comb lined up at equal intervals on the frequency axis for each repetition frequency f _rep .

Next, the interference signal intensity detector 162 detects the light intensity separated for each mode of the optical frequency comb for each of the first and second interference signals. At this time, an electrical signal having a frequency of the frequency shift amount f _b by the frequency shifter 141 is detected for each mode of the optical frequency comb.
The interference signal intensity detection unit 162 derives and digitizes the difference between the detected electrical signals for the same mode of the optical frequency comb of the first and second interference signals. The difference between the digitized first and second interference signals is proportional to the light intensity I _b of the interference signal and is expressed as in Expression (5).

I _b ∝E ₁ E ₂ exp {− (1 / τ ₀ + σ * n * c / 2) t} sin (2πf _b + φ _b ) Equation (5)

In Expression (5), φ _b is an initial phase difference between φ _s and φ _r .
In the case of using a conventional laser light source, the accuracy of the light intensity I _b derived from the equation (5) varies due to the influence of fluctuation of the frequency shift amount f _b , but in this embodiment, By using a CEO-locked optical frequency comb light source, the light intensity I _b can be derived with high accuracy from the equation (5).
Furthermore, as shown in Equation (5), the value of (σ * n * c), which is a material-specific attenuation coefficient that determines the attenuation lifetime of light in the optical cavity, is ½ that of the conventional CRDS method. It can be seen that the light decay time in the optical cavity is extended.

Here, the optical intensity I _b of the interference signal derived from the equation (5) is shown in FIG. Figure 2 is a ring length of the optical cavity is 1 m, the reflectivity 99.9%, σ * n * c = 5 * 10 -2 s - 1 (σ: absorption cross-section of the sample, n: number density of the sample, c : Light speed), the light intensity of the leaked light observed only by the reflection of the mirror of this optical cavity is (a), and the light intensity of the leaked light when the probe light and the reference light in this embodiment are used. Is shown in (b). In addition, the light intensity of the leakage light observed by the conventional CRDS method is shown in (c).
As apparent from FIGS. 2B and 2C, the measurement result shown in FIG. 2B extends the decay time of the light intensity of the leaked light, and is a highly sensitive precision spectroscopic measurement. I understand.

In this way, the CEO-locked optical frequency comb light source is bifurcated into the probe light and the reference light, and is output from the cavity in the vacuum state after frequency-shifting with the probe light absorbed by the CRDS method on the measurement object. After deriving an interference signal obtained by interfering with the reference light, the interference signal is branched again. Thereafter, by deriving the difference between the branched interference signals, the attenuation time of the measurement object can be extended. Specifically, as is clear from the equation (5), it can be seen that the value of σ * n * c, which is a material specific attenuation coefficient, is halved from that of the conventional CRDS method.
Therefore, even for a substance having a large attenuation coefficient that would deteriorate the measurement sensitivity in the conventional CRDS method, that is, a substance that shortens the attenuation lifetime of light in the optical cavity, the influence of the attenuation coefficient on the measurement sensitivity is affected. It can be mitigated and enables precise spectroscopic measurement by multi-wavelength simultaneous absorption spectroscopy using a CEO-locked optical frequency comb light source.

[Second Embodiment]
FIG. 3 is a diagram showing a configuration of a multi-wavelength simultaneous absorption spectrometer according to the second embodiment of the present invention. The multi-wavelength simultaneous absorption spectroscopic device of this embodiment has an optical configuration in which the interference signal deriving unit and the interference signal adjusting unit of the multi-wavelength simultaneous absorption spectroscopic device 10 described in the first embodiment include a delay mechanism, an optical path switching mechanism, and the like. As a component, and further includes a computer having a function of controlling an optical mechanism or the like in order to improve the measurement sensitivity characteristic.
As shown in FIG. 3, the multi-wavelength simultaneous absorption spectrometer 20 according to the present embodiment includes a CEO-locked optical frequency comb light source unit 110, a branching unit 120, a probe light extraction unit 130, and a reference light extraction unit 140. And an interference signal deriving unit 250 and an interference signal adjusting unit 260.

Among them, the interference signal deriving unit 250 includes a delay mechanism 251 (for example, configured with a mirror and a single-axis stage), optical path switching mechanisms 252a and 252b (for example, flippers), and a detector (beam). Splitter) 254.
Further, the interference signal adjustment unit 260 is a light composed of variable ND (Neutral Density) filters 261-1a and 261-1b, optical path switching mechanisms 261-2a and 261-2b (for example, flippers), and a photodetector 261-3. Intensity adjustment unit 261, optical bandpass filters 262-1a, 262-1b, optical frequency comb mode separation units (optical elements and photodetectors) 262-2a, 262-2b, and electrical signal bandpass filters 262-2a, 262 -3b, and an interference signal intensity detection unit 263 that realizes a function by a computer.

FIG. 4 is a block diagram showing a configuration example of a computer 263 that can be additionally employed to further improve the measurement sensitivity characteristic of absorption spectroscopy using the CEO-locked optical frequency comb light source of the present invention.
The computer 263 takes the difference of the electrical signal for each optical frequency comb of the same frequency from the optical detectors of the optical frequency comb mode separation units 262-2a and 262-2b, and digitizes the difference.
In order to maximize the SNR of the interference signal, first, laser intensity measurement branched into two by the beam splitter 254 is performed using the optical path switching mechanisms 261-1a and 261-2b.
Thereafter, the measurement sensitivity characteristic control unit 263-2 is used to automatically adjust the delay mechanism 251 to maximize the signal calculated by the interference signal analysis unit 263-1.
Subsequently, the variable ND filters 261-1a and 261-1b are adjusted in the case of the optical configuration of FIG. 3, and the half-wave plates 361-1a and 361-1b are adjusted in the case of the optical configuration of FIG. The intensity ratio detected by the detector 261-3 is automatically adjusted evenly.

[Third Embodiment]
FIG. 5 is a diagram showing a configuration of a multi-wavelength simultaneous absorption spectrometer according to the third embodiment of the present invention. The multi-wavelength simultaneous absorption spectrometer according to this embodiment uses a polarization beam splitter as means for combining and re-branching laser light in the configuration of the multi-wavelength simultaneous absorption spectrometer described in the second embodiment. Thus, an interference signal is derived.

As shown in FIG. 5, the multi-wavelength simultaneous absorption spectroscopic device 30 combines the two-branched laser pulses again at the same time by the polarization beam splitter 354 and again branches them into two. Here, in order to set the branching ratio to 1: 1, the probe light intensity is automatically adjusted by the half-wave plates 361-1a and 361-1b and the computer 263. The interference signal is detected by each optical frequency comb, and the signal is detected at the frequency of the frequency shift amount f _{b in} the frequency shifter 141. Therefore, the electric signal bandpass filters 262-3a and 262-3b are used and other than f _b Is removed.
The electric signal input to the computer 263 takes the difference of the electric signal for each optical frequency comb of the same frequency at the two input ports and digitizes it.

As described above, when the polarization beam splitter is used, the detection noise level is reduced by about 50 dB as compared with the normal CRDS method, so that the improvement of the signal-to-noise ratio (SNR) in the detection of the interference signal is further improved.
Therefore, it is possible to realize precise measurement by high-sensitivity absorption spectroscopy by extending the decay time and improving the SNR.

  Such a multi-wavelength simultaneous absorption spectroscopic apparatus can be used for a high-sensitivity measurement apparatus based on long-high-resolution absorption spectroscopy using a CEO-locked optical frequency comb stabilized light source.

  DESCRIPTION OF SYMBOLS 10,20,30 ... Multiple wavelength simultaneous absorption spectroscopy apparatus, 110 ... Optical frequency comb light source part, 120 branch part, 130 ... Probe light extraction part, 131 ... Optical cavity (for sample installation), 140 ... Reference light extraction part, 141 ... frequency shifter, 142 ... optical cavity (vacuum state), 150250, 350 ... interference signal deriving unit, 160, 260, 360 ... interference signal adjusting unit, 161, 261, 361 ... light intensity adjusting unit, 162, 262 ... interference signal Spectroscopic unit, 163, 263 ... interference signal intensity detection unit, 251 ... delay mechanism, 252a, 252b, 261-2a, 261-2b ... optical path switching mechanism, 253, 261-3 ... photodetector, 254 ... beam splitter (light Coupler), 261-1a, 261-1b, variable ND filter, 262-1a, 262-ab, optical bandpass filter, 262 2a, 262-2b ... optical frequency comb mode separator (optical element and photodetector), 262-3a, 262-3b ... electric signal band pass filter, 263-1 ... interference signal analysis unit, 263-2 ... measurement sensitivity Characteristic control unit, 354... Polarization beam splitter, 361-1a, 361-1b... Half wave plate, 60... Optical cavity, 61 high reflectivity mirror.

Claims (5)

A carrier envelope offset (CEO) locked optical frequency comb light source;
A branching section for branching the laser beam output from the optical frequency comb light source into two laser beams;
A probe light extraction unit that extracts one of the laser beams branched by the branching unit as a probe light and enters the first cavity in which the measurement object is placed and leaks from the first cavity. When,
The frequency of the laser beam branched by the branching unit is shifted with the other laser beam as a reference beam, and the reference beam with the shifted frequency has the same configuration as that of the first cavity in which the object to be measured is installed, and a vacuum. A reference light extraction unit that extracts the reference light that enters the second cavity in a state and leaks out of the second cavity ;
An interference signal deriving unit that causes interference between the probe light extracted by the probe light extracting unit and the reference light extracted by the reference light extracting unit;
An interference signal adjusting unit that divides the interference signal measured by the interference signal deriving unit to derive the light intensity for each mode of the optical frequency comb of the interference signal , and
The interference signal deriving unit
Re-branching the interference signal obtained by combining the probe light extracted by the probe light extraction unit and the reference light extracted by the reference light extraction unit into a first interference signal and a second interference signal;
The interference signal adjustment unit is
Multi-wavelength simultaneous absorption , wherein light intensity for each mode of an optical frequency comb of the interference signal is derived from the first interference signal and the second interference signal derived by the interference signal deriving unit. Spectrometer. The multi-wavelength simultaneous absorption spectrometer according to claim 1,
The interference signal adjustment unit is
An interference signal spectroscopic unit that splits the first and second interference signals for each mode of an optical frequency comb;
A multi-wavelength simultaneous absorption spectroscopic apparatus comprising: an interference signal intensity detection unit that detects a difference between the first and second interference signals that are spectrally separated for each mode of the optical frequency comb by the interference signal spectroscopic unit. . The multi-wavelength simultaneous absorption spectrometer according to claim 1 or 2 ,
The interference signal adjustment unit is
A light intensity adjusting unit that adjusts a signal-to-noise ratio of the interference signal by adjusting a light intensity between the first interference signal and the second interference signal derived by the interference signal deriving unit.
A multi-wavelength simultaneous absorption spectroscopic device comprising: The multi-wavelength simultaneous absorption spectrometer according to any one of claims 1 to 3 ,
The multi-wavelength simultaneous absorption spectrometer , wherein the interference signal deriving unit is a polarization beam splitter . A multi-wavelength simultaneous absorption spectroscopy method using a carrier envelope offset (CEO) locked optical frequency comb light source,
A branching step for branching the laser beam output from the CEO-locked optical frequency comb light source into two laser beams;
A probe light extraction step for extracting one of the laser beams branched by the branching step into the first cavity where the measurement object is placed by using one of the laser beams as the probe light and extracting the probe light leaking from the first cavity. When,
Shifting the frequency of the other laser beam as a reference beam of laser light branched by said branching step, the first and vacuum the same configuration as the cavities of the reference light obtained by shifting the frequency installing the measurement object A reference light extraction step for extracting reference light that enters the second cavity in a state and leaks out of the second cavity ;
An interference signal deriving step for causing the probe light extracted by the probe light extraction step to interfere with the reference light extracted by the reference light extraction step;
The interference signal derived by spectrally interference signal derived by step have a interference signal adjustment step of deriving the intensity of each mode of the optical frequency comb of the interference signal,
The interference signal derivation step includes:
Re-branching the interference signal obtained by combining the probe light extracted in the probe light extraction step and the reference light extracted in the reference light extraction step into a first interference signal and a second interference signal;
The interference signal adjustment step includes:
Multi-wavelength simultaneous absorption , wherein an optical intensity for each mode of an optical frequency comb of the interference signal is derived from the first interference signal and the second interference signal derived by the interference signal deriving step. Spectroscopic method.

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