Spectral peak online calibration system and method for dual-optical comb coherent Raman spectrum measurement

Abstract

According to the spectrum peak online calibration system and method for double-optical-comb coherent Raman spectrum measurement, a calibration sample of a Raman shift wave number corresponding to a known spectrum peak is arranged in a spectrum peak calibration module, a coherent Raman spectrum of the calibration sample is measured, and a transformation function of delay and the Raman shift wave number is calculated; the spectrum peak on-line calibration device realizes spectrum peak on-line calibration of double-optical-comb coherent Raman spectrum measurement, is beneficial for reducing spectrum peak calibration deviation caused by system fluctuation, and is characterized by comprising an optical comb light source module, a dispersion regulation and control module, a spectrum peak calibration module and a sample detection module which are connected in sequence, the optical comb light source module generates pump light and Stokes light which are different in frequency and vertical in polarization, and the Stokes light is connected with the optical comb light source module. The dispersion regulation and control module enables the pump light and the Stokes light to form combined light, the spectrum peak calibration module divides the combined light into transmission light and reflection light, the reflection light acts on a calibration sample to generate a calibration spectrum signal, and the transmission light acts on the sample to measure a coherent Raman spectrum signal of the sample. And the spectrum signals and the calibration spectrum signals are recorded by the high-speed data acquisition system and input into an upper computer.

Description

Technical Field

[0001] The present invention relates to the technical field of coherent Raman spectroscopy measurement, and in particular to a spectrum peak online calibration system and method for dual-comb coherent Raman spectroscopy measurement. A calibration sample of the Raman shift wavenumber corresponding to a known spectrum peak is set in a spectrum peak calibration module, and its coherent Raman spectrum is measured. A transformation function of a delay and a Raman shift wavenumber is calculated to achieve the spectrum peak online calibration of the dual-comb coherent Raman spectroscopy measurement, which is beneficial to reducing the spectrum peak calibration deviation caused by system fluctuations and improving the spectrum measurement accuracy. Background Art

[0002] Coherent Raman scattering is a Raman scattering technology based on nonlinear effects. This method uses the multi-beam interference effect to obtain a coherent Raman signal with greatly increased intensity. Coherent Raman spectral signals directly reflect the molecular vibration mode inside the material and have non-destructive and non-label detection capabilities. At the same time, due to the high signal-to-noise ratio, its measurement time is extremely short, so it can be widely used in biomedical imaging, real-time chemical analysis, industrial environmental monitoring and other fields. Dual-comb coherent Raman spectroscopy uses two optical comb light sources as pump light and Stokes light to achieve the excitation of coherent Raman scattering. The center frequency difference between the two optical combs determines the excited molecular vibration frequency. In order to achieve wide spectral range and high-speed spectral measurement, a spectral focusing method is used for excitation. This method applies linear chirping to the pump light and Stokes pulses so that the instantaneous frequency of the pulse changes linearly with time, so that different pulse delays correspond to the excitation of different molecular vibration frequencies; then the delay difference between the pump light and the Stokes light is scanned, and the obtained time domain signal has a horizontal coordinate of delay and a vertical coordinate of vibration intensity. Therefore, it is necessary to calibrate the measured signal and convert the delay into Raman wavenumber to obtain accurate coherent Raman spectrum signal.

[0003] The inventors learned that when the two optical combs in the coherent Raman spectroscopy measurement system are affected by ambient temperature, vibration, etc., the repetition frequency, repetition frequency difference and other parameters of the output laser pulses will change, which causes the relative delay of the two optical comb laser pulses to jitter. Due to the use of spectral focusing excitation, this causes the wave number of the generated coherent Raman spectroscopy signal to shift and the signal to be distorted. The inventors believe that if the Raman shift wave number and delay at the time of sample measurement can be calibrated online, even if the system parameters fluctuate, the Raman shift wave number and delay conversion function at that moment can be obtained, so as not to be affected by the fluctuation of system parameters. Therefore, if a peak calibration module is additionally set in the system, and a method for obtaining the Raman shift wave number and delay conversion function at that moment using a sample with a known peak position, the peak online calibration can be completed, which helps to know the influence of system fluctuations on measurement and improve the accuracy of spectral measurement. At present, there is no system and method for online calibration of the peak of dual-comb coherent Raman spectroscopy. In view of this, the inventors have completed the present invention. Summary of the invention

[0004] In view of the defects or shortcomings of the prior art, the present invention provides a system and method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement. A calibration sample of the Raman shift wavenumber corresponding to a known spectrum peak is set in a spectrum peak calibration module, and its coherent Raman spectrum is measured. A transformation function of the delay and the Raman shift wavenumber is calculated to achieve online calibration of the spectrum peaks in dual-comb coherent Raman spectroscopy measurement, which is beneficial to reducing the spectrum peak calibration deviation caused by system fluctuations and improving the accuracy of spectrum measurement.

[0005] The technical solution of the present invention is as follows: A spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement, characterized in that it comprises a comb light source module, a dispersion control module, a spectrum peak calibration module and a sample detection module connected in sequence, wherein the comb light source module generates pump light and Stokes light with different frequencies and perpendicular polarizations, the dispersion control module applies equal amounts of dispersion to the pump light and the Stokes light and compensates for their delay difference to form a combined light beam, the spectrum peak calibration module divides the combined light beam into transmitted light and reflected light, the reflected light acts on a calibration sample to generate a calibration spectrum signal, the transmitted light is injected into the sample detection module to act on the sample to measure the coherent Raman spectrum signal of the sample, and is recorded by a high-speed data acquisition system together with the calibration spectrum signal and input into a host computer for processing to realize the online calibration of the spectrum peak of the sample coherent Raman spectrum.

[0006] The optical comb light source module includes a first optical frequency comb and a second optical frequency comb respectively connected to a reference source, the output side of the first optical frequency comb is connected to the first grating pair in the dispersion control module, and the output side of the second optical frequency comb is connected to the second grating pair in the dispersion control module through a 1 / 2 wave plate.

[0007] The dispersion control module includes a polarization beam splitter prism, the output side of the polarization beam splitter prism is connected to the depolarization beam splitter in the spectrum peak calibration module, the first input side of the polarization beam splitter prism is connected to the second grating pair, and the second input side of the polarization beam splitter prism is connected to the first grating pair through an aspheric lens pair, a first reflector and a retroreflective mirror in sequence.

[0008] The spectrum peak calibration module includes a first photomultiplier tube, the output side of the first photomultiplier tube is connected to the high-speed data acquisition system in the sample detection module, the input side of the first photomultiplier tube is connected to the reflection side of the depolarizing beam splitter through a first focusing lens, a first filter, a second objective lens, a calibration sample and the first objective lens in sequence, and the transmission side of the depolarizing beam splitter is connected to the second reflector in the sample detection module.

[0009] The sample detection module includes a sample stage, the input side of the sample stage is connected to the second reflector through the third objective lens, and the output side of the sample stage is connected to the host computer through the fourth objective lens, the second filter, the second focusing lens, the second photomultiplier tube and the high-speed data acquisition system in sequence.

[0010] The reference signal frequency provided by the reference source is 100 MHz, the center frequency repetition frequency of the first optical frequency comb is 100 MHz, the repetition frequency of the second optical frequency comb is 100 MHz, the repetition frequency difference between the first optical frequency comb and the second optical frequency comb is adjustable, and the adjustable range of the repetition frequency difference is 0 to 100 Hz. The output spectrum range of the first optical frequency comb is λ 1-min To 1-max ,λ 1-min is the first wavelength λ 1 Minimum value, λ 1-max is the first wavelength λ 1 Maximum value, the second optical frequency comb output spectrum range is λ 2-min To 2-max ,λ 2-min is the second wavelength λ 2 Minimum value, λ 2-max is the second wavelength λ 2 The maximum value, where λ 1-max <λ 2-min .

[0011] The gratings in the first grating pair and the second grating pair are blazed gratings, and the blazing wavelength of the gratings in the first grating pair is in the range of λ 1 The blazing wavelength of the second grating pair is near λ 2 nearby.

[0012] The transmission and reflection ratio of the depolarizing beam splitter is 7:3, and the Raman spectrum of the calibration sample is to There are at least 5 Raman peaks with known peak positions within the wavenumber range.

[0013] The first filter and the second filter are both low-pass filters with a cut-off wavelength of .

[0014] A method for online calibration of spectrum peaks for dual-comb coherent Raman spectroscopy measurement, characterized in that the online calibration system for spectrum peaks for dual-comb coherent Raman spectroscopy measurement is used to perform online calibration of spectrum peaks for the dual-comb coherent Raman spectroscopy measurement system, comprising the following steps: Step 1, turn on the first optical frequency comb and the second optical frequency comb, lock their repetition frequency difference, adjust the position of the retroreflector, and observe the spectral signal of the calibration sample in the host computer until the signal is maximum and near the center of the time axis; Step 2: Observe the spectral signal of the calibration sample in the host computer, select 5 spectral peaks, and record the Raman shift wavenumber w corresponding to the spectral peaks. 1 、w 2 、w 3 、w 4 and w 5 , and its delay d on the time axis 1 d 2 d 3 d 4 and d 5 ; Step 3, use the formula to fit the transformation function of delay x and Raman shift wave number y, the formula is:

[0015] where w i 、w j is the recorded Raman shift wave number, d i d j Delay for recording; Step 4: Use the host computer to record the coherent Raman spectrum signal of the sample, and use the formula in step 3 to convert its delay on the time axis into wave number, thereby completing the online wave number calibration.

[0016] The technical effects of the present invention are as follows: The present invention is an online calibration system and method for spectrum peaks of dual-comb coherent Raman spectroscopy measurement, which realizes the online calibration of spectrum peaks of dual-comb coherent Raman spectroscopy measurement by setting a calibration sample of the Raman shift wavenumber corresponding to the known spectrum peak in the spectrum peak calibration module, measuring its coherent Raman spectrum, and calculating the transformation function of the delay and the Raman shift wavenumber, which is beneficial to reduce the spectrum peak calibration deviation caused by system fluctuations and improve the accuracy of spectrum measurement. The present invention is an online calibration system and method for spectrum peaks of dual-comb coherent Raman spectroscopy measurement system, which uses a known spectrum peak Raman shift sample to convert the transformation function of the Raman shift wavenumber and the delay.

[0017] The advantages of the present invention over the prior art are as follows: (1) Compared with conventional coherent Raman scattering spectrum measurement devices, the present invention uses samples with known spectral peaks corresponding to Raman wavenumbers to perform real-time calculations of the transformation function of Raman shift wavenumbers and delays, thereby solving the problem of being unable to perform real-time calibration of spectral peaks and improving the accuracy of spectral measurement. (2) Real-time monitoring of delays can be achieved without the need to set up a separate delay monitoring module, thereby simplifying the system. (3) A high-speed data acquisition system is used to collect spectral information, thereby improving the speed of spectral measurement and online calibration of spectral peaks. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic structural diagram of a spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement. Figure 1The system includes a light comb light source module, a dispersion control module, a spectrum peak calibration module, and a sample detection module which are connected in sequence.

[0019] Figure 2 The present invention is a schematic flow chart of a method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement. Figure 2 The method comprises the steps of: 1, opening the first optical frequency comb and the second optical frequency comb, locking their repetition frequency difference, and adjusting the position of the retroreflector so that the spectral signal is maximized and near the center of the time axis; 2, observing the spectral signal of the calibration sample in the host computer, selecting 5 spectral peaks, and recording the Raman shift wavenumbers corresponding to the spectral peaks and the delay on the time axis; 3, using a formula to fit the transformation function of the delay x and the Raman shift wavenumber y; and 4, using the host computer to record the coherent Raman spectral signal of the sample, and using the formula to convert its delay on the time axis into wavenumbers.

[0020] Figure 3 It is the measured spectrum of the calibration sample. Figure 3 The horizontal axis is delay (ps, scale value -10, -8, ···, 10), and the vertical axis is signal strength (au- arbitrary unit, scale value 0, 5000, ···, 20000). Figure 3 The calibration specimen involved is PS (polystyrene) sample.

[0021] Figure 4 It is the Raman shift wavenumber diagram of the calibration sample. Figure 4 The horizontal axis is the Raman shift wave number (cm -1 , scale value 2800, 2850, ···, 3200), the vertical axis is the signal strength (au, scale value 0, 5000, ···, 20000). Figure 4 The calibration specimen involved is PS (polystyrene) sample.

[0022] Figure 5 This is the fitted delay and Raman shift wavenumber conversion function diagram. Figure 5 The horizontal axis is the delay (ps, scale value -10, -8, ···, 10), and the vertical axis is the Raman shift wave number (cm -1 , scale values ​​2800, 2850,..., 3200). Figure 5 The dots in the middle represent the actual measured values, and the oblique lines associated with the dots are the fitted curves.

[0023] The reference numerals are as follows: 1-first optical frequency comb; 2-second optical frequency comb; 3-reference source; 4-1 / 2 wave plate; 5-first grating pair; 6-second grating pair; 7-retroreflecting mirror; 8-first reflector; 9-aspherical lens pair; 10-polarization beam splitter; 11-depolarization beam splitter; 12-first objective lens; 13-calibration sample; 14-second objective lens; 15-first filter; 16-first focusing lens; 17-first photomultiplier tube; 18-second reflector; 19-third objective lens; 20-sample stage; 21-fourth objective lens; 2-second filter; 23-second focusing lens; 24-second photomultiplier tube; 25-high-speed data acquisition system; 26-host computer. DETAILED DESCRIPTION

[0024] Below is the attached figure ( Figure 1-Figure 5 ) and examples illustrate the present invention.

[0025] Figure 1 The present invention is a schematic structural diagram of a spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement. Figure 2 The present invention is a schematic flow chart of a method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement. Figure 3 It is the measured spectrum of the calibration sample. Figure 4 It is the Raman shift wavenumber diagram of the calibration sample. Figure 5 This is the fitted delay and Raman shift wave number conversion function diagram. Figures 1 to 5 As shown, a spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement includes a light comb light source module, a dispersion control module, a spectrum peak calibration module and a sample detection module connected in sequence, wherein the light comb light source module generates pump light and Stokes light with different frequencies and perpendicular polarizations, the dispersion control module applies equal amounts of dispersion to the pump light and the Stokes light and compensates for their delay difference to form a combined light beam, the spectrum peak calibration module divides the combined light beam into transmitted light and reflected light, the reflected light acts on a calibration sample 13 to generate a calibration spectrum signal, the transmitted light is injected into the sample detection module and acts on a sample (the sample is in a sample stage 20) to measure the coherent Raman spectrum signal of the sample, and is recorded together with the calibration spectrum signal by a high-speed data acquisition system 25 and input into a host computer 26 for processing to realize the online calibration of the spectrum peak of the sample coherent Raman spectrum.

[0026] The optical comb light source module comprises a first optical frequency comb 1 and a second optical frequency comb 2 respectively connected to a reference source 3, the output side of the first optical frequency comb 1 is connected to a first grating pair 5 in the dispersion control module, and the output side of the second optical frequency comb 2 is connected to a second grating pair 6 in the dispersion control module through a 1 / 2 wave plate 4. The dispersion control module comprises a polarization beam splitter prism 10, the output side of the polarization beam splitter prism 10 is connected to a depolarization beam splitter 11 in the spectrum peak calibration module, the first input side of the polarization beam splitter prism 10 is connected to the second grating pair 6, and the second input side of the polarization beam splitter prism 10 is connected to the first grating pair 5 through an aspheric lens pair 9, a first reflector 8 and a retroreflector 7 in sequence.

[0027] The spectrum peak calibration module includes a first photomultiplier tube 17, the output side of the first photomultiplier tube 17 is connected to the high-speed data acquisition system 25 in the sample detection module, the input side of the first photomultiplier tube 17 is connected to the reflection side of the depolarizing beam splitter 11 through the first focusing lens 16, the first filter 15, the second objective lens 14, the calibration sample 13 and the first objective lens 12 in sequence, and the transmission side of the depolarizing beam splitter 11 is connected to the second reflector 18 in the sample detection module. The sample detection module includes a sample stage 20, the input side of the sample stage 20 is connected to the second reflector 18 through the third objective lens 19, and the output side of the sample stage 20 is connected to the host computer 26 through the fourth objective lens 21, the second filter 22, the second focusing lens 23, the second photomultiplier tube 24 and the high-speed data acquisition system 25 in sequence.

[0028] The reference signal frequency provided by the reference source 3 is 100 MHz, the center frequency repetition frequency of the first optical frequency comb is 100 MHz, the repetition frequency of the second optical frequency comb is 100 MHz, the repetition frequency difference between the first optical frequency comb and the second optical frequency comb is adjustable, and the adjustable range of the repetition frequency difference is 0 to 100 Hz. The output spectrum range of the first optical frequency comb is λ 1-min To 1-max ,λ 1-min is the first wavelength λ 1 Minimum value, λ 1-max is the first wavelength λ 1 Maximum value, the second optical frequency comb output spectrum range is λ 2-min To 2-max ,λ 2-min is the second wavelength λ 2 Minimum value, λ 2-min is the second wavelength λ 2 The maximum value, where λ 1-max <λ 2-min The gratings in the first grating pair and the second grating pair are blazed gratings, and the blazing wavelength of the gratings in the first grating pair is λ 1 The blazing wavelength of the second grating pair is near λ2 nearby.

[0029] The transmission and reflection ratio of the depolarizing beam splitter is 7:3, and the Raman spectrum of the calibration sample is to There are at least 5 Raman peaks with known peak positions within the wavenumber range.

[0030] The first filter and the second filter are both low-pass filters with a cut-off wavelength of .

[0031] A method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement is disclosed. The method adopts the above-mentioned online calibration system for spectrum peaks in dual-comb coherent Raman spectroscopy measurement to perform online calibration of spectrum peaks on the dual-comb coherent Raman spectroscopy measurement system, and comprises the following steps: step 1, turning on the first optical frequency comb and the second optical frequency comb, locking their repetition frequency difference, adjusting the position of the retroreflector, and observing the spectrum signal of the calibration sample in the host computer until the signal is maximum and near the center of the time axis; step 2, observing the spectrum signal of the calibration sample in the host computer, selecting 5 spectrum peaks, and recording the Raman shift wavenumbers w corresponding to the spectrum peaks. 1 、w 2 、w 3 、w 4 and w 5 , and its delay d on the time axis 1 d 2 d 3 d 4 and d 5 ; Step 3, use the formula to fit the transformation function of delay x and Raman shift wave number y, the formula is:

[0032] where w i 、w j is the recorded Raman shift wave number, d i d j Delay for recording; Step 4: Use the host computer to record the coherent Raman spectrum signal of the sample, and use the formula in step 3 to convert its delay on the time axis into wave number, thereby completing the online wave number calibration.

[0033] A system and method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement, which realizes online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement by setting a calibration sample of Raman shift wavenumbers corresponding to known spectrum peaks in a spectrum peak calibration module, measuring its coherent Raman spectrum, and calculating a transformation function of delay and Raman shift wavenumber, thereby reducing the spectrum peak calibration deviation caused by system fluctuations and improving the accuracy of spectrum measurement.

[0034] refer to Figure 1As shown, a spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement includes a light comb light source module, a dispersion control module, a spectrum peak calibration module and a sample detection module connected in sequence, the light comb light source module generates pump light and Stokes light with different frequencies and perpendicular polarizations, the dispersion control module applies equal amounts of dispersion to the pump light and the Stokes light and compensates for their delay difference to form a combined light beam, the spectrum peak calibration module divides the combined light beam into transmitted light and reflected light, the reflected light acts on a calibration sample 13 to generate a calibration spectrum signal, the transmitted light is injected into the sample detection module to act on the sample to measure the coherent Raman spectrum signal of the sample, and is recorded by a high-speed data acquisition system 25 together with the calibration spectrum signal and input into a host computer 26 for processing to realize the online calibration of the spectrum peak of the sample coherent Raman spectrum.

[0035] The optical comb light source module includes a 1 / 2 wave plate 4, which is connected to the output side of the second optical frequency comb 2. The first optical frequency comb 1 and the second optical frequency comb 2 are respectively connected to a reference source 3. The output side of the first optical frequency comb 1 and the output side of the 1 / 2 wave plate 4 are respectively connected to a dispersion control module.

[0036] The dispersion control module includes a first grating pair 5 and a second grating pair 6, the input side of the first grating pair 5 is connected to the output side of the first optical frequency comb 1, the output side of the first grating pair 5 is connected to the input side of the retroreflector 7, the output side of the retroreflector 7 is connected to the first input side of the polarization beam splitter prism 10 through the first reflector 8 and the aspheric lens pair 9 in sequence, the input side of the second grating pair 6 is connected to the output side of the 1 / 2 wave plate 4, the output side of the second grating pair 6 is connected to the second input side of the polarization beam splitter prism 10, and the output side of the polarization beam splitter prism 10 is connected to the spectrum peak calibration module.

[0037] The spectrum peak calibration module includes a depolarizing beam splitter 11 and a calibration sample 13. The input side of the depolarizing beam splitter 11 is connected to the output side of the polarization beam splitter prism 10. The reflection side of the depolarizing beam splitter 11 is sequentially connected to the first objective lens 12, the calibration sample 13, the second objective lens 14, the first filter 15, the first focusing lens 16 to the first photomultiplier tube 17. The signal of the first photomultiplier tube 17 is connected to the high-speed data acquisition system 25 of the sample detection module. The transmission side of the depolarizing beam splitter 11 is connected to the second reflector 18 of the sample detection module.

[0038] The sample detection module includes a second photomultiplier tube 24, a second focusing lens 23, a second filter 22, a fourth objective lens 21, a sample stage 20, a third objective lens 19 and a second reflector 18 connected to the transmission side of the depolarizing beam splitter 11, and the signal of the second photomultiplier tube 24 is connected to the host computer 26 through a high-speed data acquisition system 25.

[0039] The reference signal frequency provided by the reference source 3 is 100 MHz, the center frequency repetition frequency of the first optical frequency comb 1 is 100 MHz, the repetition frequency of the second optical frequency comb 2 is 100 MHz, the repetition frequency difference between the first optical frequency comb 1 and the second optical frequency comb 2 is adjustable, and the adjustable range of the repetition frequency difference is 0 to 100 Hz. The output spectrum range of the first optical frequency comb 1 is λ 1-min To 1-max , the output spectrum range of the second optical frequency comb 2 is λ 2-min To 2-max , where λ 1-max <λ 2-min .

[0040] The gratings in the first grating pair 5 and the second grating pair 6 are blazed gratings, and the blazing wavelength of the gratings in the first grating pair 5 is in the range of λ 1 The blazing wavelength of the second grating pair 6 is near λ 2 nearby.

[0041] The transmission and reflection ratio of the depolarizing beam splitter 11 is 7:3, and the Raman spectrum of the calibration sample 13 is to There are more than 5 Raman peaks with known peak positions within the wavenumber range.

[0042] The first filter 15 and the second filter 22 are both low-pass filters with a cut-off wavelength of .

[0043] A method for online calibration of spectrum peaks for dual-comb coherent Raman spectroscopy measurement is provided, wherein the online calibration system for spectrum peaks for dual-comb coherent Raman spectroscopy measurement is used to perform online calibration of spectrum peaks for the dual-comb coherent Raman spectroscopy measurement system, and the method comprises the following steps: Step 1, turn on the first optical frequency comb 1 and the second optical frequency comb 2, lock their repetition frequency difference, adjust the position of the retroreflector 7, and observe the spectral signal of the calibration sample 13 in the host computer 26 until the signal is maximum and near the center of the time axis; Step 2: Observe the spectral signal of the calibration sample 13 in the host computer 26, select 5 spectral peaks, and record the Raman shift wavenumbers corresponding to the spectral peaks as w 1 、w 2 、w 3 、w 4 and w 5， And its delay d on the time axis 1 d 2 d 3 d 4 and d 5 ; Step 3, use the formula to fit the transformation function of delay x and Raman shift wave number y, the formula is:

[0044] where w i 、w j is the recorded Raman shift wave number, d i d j Delay for recording.

[0045] Step 4, using the host computer 26 to record the coherent Raman spectrum signal of the sample, and using the formula in step 3 to convert its delay on the time axis into wave number, thereby completing the online wave number calibration.

[0046] Specifically, the laser emitted by the optical comb light source module obtains an equal amount of linear chirp through the first grating pair 5 and the second grating pair 6 in the dispersion control module, and then adjusts the time overlap through the retroreflector 7 and the spatial overlap through the aspheric lens pair 9, and then forms a combined light through the polarization beam splitter prism 10. The combined light is split into two beams through the depolarization beam splitter 11, and the reflected beam of the depolarization beam splitter 11 acts on the calibration sample (taking PS (polystyrene) sample as an example) 13 with a Raman shift corresponding to a known spectral peak to obtain the following: Figure 3 The calibration sample spectrum shown in FIG. 1 is observed by the host computer 26 at this time, and the spectrum is obtained according to the known peak Raman shift ( Figure 4 ), use Figure 2 The method shown fits the delay and Raman shift wavenumber transform function ( Figure 5 ), and at the same time, the transmitted beam through the depolarizing beam splitter 11 interacts with the sample incident into the sample detection module to obtain a sample horizontal axis with a delayed spectrum signal such as Figure 3 As shown in FIG. 1 , the delay and Raman shift wave number conversion function is used to process it, and finally the coherent Raman spectrum after online calibration of the spectrum peak is obtained, as shown in FIG. Figure 4 shown.

[0047] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A spectrum peak online calibration system for dual-comb coherent Raman spectroscopy measurement, characterized in that: The invention comprises an optical comb light source module, a dispersion control module, a spectrum peak calibration module and a sample detection module which are connected in sequence. The optical comb light source module generates pump light and Stokes light with different frequencies and perpendicular polarizations. The dispersion control module applies equal dispersion to the pump light and the Stokes light and compensates for their delay difference to form a combined light beam. The spectrum peak calibration module divides the combined light beam into transmitted light and reflected light. The reflected light acts on a calibration sample to generate a calibration spectrum signal. The transmitted light is injected into the sample detection module to act on the sample to measure the coherent Raman spectrum signal of the sample, and is recorded by a high-speed data acquisition system together with the calibration spectrum signal and input into a host computer for processing to realize online calibration of the spectrum peak of the sample coherent Raman spectrum.

2. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 1, characterized in that: The optical comb light source module includes a first optical frequency comb and a second optical frequency comb respectively connected to a reference source, the output side of the first optical frequency comb is connected to the first grating pair in the dispersion control module, and the output side of the second optical frequency comb is connected to the second grating pair in the dispersion control module through a 1 / 2 wave plate.

3. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 1, characterized in that: The dispersion control module includes a polarization beam splitter prism, the output side of the polarization beam splitter prism is connected to the depolarization beam splitter in the spectrum peak calibration module, the first input side of the polarization beam splitter prism is connected to the second grating pair, and the second input side of the polarization beam splitter prism is connected to the first grating pair through an aspheric lens pair, a first reflector and a retroreflective mirror in sequence.

4. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 1, characterized in that: The spectrum peak calibration module includes a first photomultiplier tube, the output side of the first photomultiplier tube is connected to the high-speed data acquisition system in the sample detection module, the input side of the first photomultiplier tube is connected to the reflection side of the depolarizing beam splitter through a first focusing lens, a first filter, a second objective lens, a calibration sample and the first objective lens in sequence, and the transmission side of the depolarizing beam splitter is connected to the second reflector in the sample detection module.

5. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 1, characterized in that: The sample detection module includes a sample stage, the input side of the sample stage is connected to the second reflector through the third objective lens, and the output side of the sample stage is connected to the host computer through the fourth objective lens, the second filter, the second focusing lens, the second photomultiplier tube and the high-speed data acquisition system in sequence.

6. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 2, characterized in that: The reference signal frequency provided by the reference source is 100 MHz, the center frequency repetition frequency of the first optical frequency comb is 100 MHz, the repetition frequency of the second optical frequency comb is 100 MHz, the repetition frequency difference between the first optical frequency comb and the second optical frequency comb is adjustable, and the adjustable range of the repetition frequency difference is 0 to 100 Hz. The output spectrum range of the first optical frequency comb is λ 1-min To 1-max ,λ 1-min is the minimum value of the first wavelength λ1, λ 1-max is the maximum value of the first wavelength λ1, and the output spectrum range of the second optical frequency comb is λ 2-min To 2-max ,λ 2-min is the minimum value of the second wavelength λ2, λ 2-max is the maximum value of the second wavelength λ2, where λ 1-max <λ 2-min .

7. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 3, characterized in that: The gratings in the first grating pair and the second grating pair are blazed gratings, the blazing wavelength of the gratings in the first grating pair is near λ1, and the blazing wavelength of the gratings in the second grating pair is near λ2.

8. The online spectral peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 4, characterized in that: The transmission and reflection ratio of the depolarizing beam splitter is 7:3, and the Raman spectrum of the calibration sample is to There are at least 5 Raman peaks with known peak positions within the wavenumber range.

9. The online peak calibration system for dual-comb coherent Raman spectroscopy measurement according to claim 5, characterized in that: The first filter and the second filter are both low-pass filters with a cut-off wavelength of .

10. A method for online calibration of spectrum peaks in dual-comb coherent Raman spectroscopy measurement, characterized in that: The online calibration system for spectrum peaks of dual-comb coherent Raman spectroscopy measurement according to any one of claims 1 to 9 is used to perform online calibration of spectrum peaks of a dual-comb coherent Raman spectroscopy measurement system, comprising the following steps: Step 1, turn on the first optical frequency comb and the second optical frequency comb, lock their repetition frequency difference, adjust the position of the retroreflector, and observe the spectral signal of the calibration sample in the host computer until the signal is maximum and near the center of the time axis; Step 2, observe the spectral signal of the calibration sample in the host computer, select 5 spectral peaks, and record the Raman shift wavenumbers w1, w2, w3, w4 and w5 corresponding to the spectral peaks, as well as their delays d1, d2, d3, d4 and d5 on the time axis; Step 3, use the formula to fit the transformation function of delay x and Raman shift wave number y, the formula is: ； where w i 、w j is the recorded Raman shift wave number, d i d j Delay for recording; Step 4: Use the host computer to record the coherent Raman spectrum signal of the sample, and use the formula in step 3 to convert its delay on the time axis into wave number, thereby completing the online wave number calibration.

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