CN105823559B - A kind of adaptive double light comb spectrally compensating method for extracting signal - Google Patents

Abstract

The invention discloses an adaptive dual-comb spectral compensation signal extraction system, which is characterized in that the adaptive dual-comb spectral compensation signal is obtained by Michelson interferometer and electrical beat frequency, and adopts the method of time domain delay and frequency domain selection, Effectively use the Michelson interferometer to coherently detect the front and rear pulses with a certain delay, and extract the signals representing the repetition frequency jitter and carrier envelope phase jitter of a single pulse laser, and finally obtain the two pulse lasers through the process of electrical frequency doubling and frequency mixing Compensation signals for relative repetition frequency jitter and relative carrier envelope phase jitter can be directly used for adaptive dual-comb spectroscopy measurement. Compared with the prior art, the present invention completely avoids the need to introduce two narrow-linewidth continuous lasers to extract the compensation signal in the adaptive dual-comb spectrum. The compensation signal is less disturbed by the continuous light wavelength drift, and the signal is stable and reliable, which further improves the Stability and reliability of an adaptive dual-comb spectroscopy system.

Description

An Adaptive Dual Optical Comb Spectral Compensation Signal Extraction Method

technical field

The invention relates to the technical field of photoelectric detection, in particular to an adaptive dual-comb spectral compensation signal extraction method based on Michelson interferometer.

Background technique

As a frontier topic in the field of scientific research in recent years, dual-comb spectroscopy technology can greatly improve the accuracy of spectral detection. Compared with the traditional technology, the dual optical comb spectral detection technology has two improvements. One is to use an optical comb to replace the traditional light source. As a standard, the position of the frequency spectral line is more stable, the line width is narrower, and the accuracy is higher; Optical combs with slightly different frequencies are measured at the same time. One is used as a reference comb and the other is used as an excitation comb, which is similar to the main scale and auxiliary scale of a vernier caliper. Through frequency misalignment and beat frequency detection, the accuracy of frequency measurement is further improved. The recently developed adaptive dual-comb spectroscopy technology uses two narrow-linewidth CW lasers and two ultrashort pulse lasers to beat frequency, and then undergoes circuit frequency mixing, frequency doubling, amplification, and filtering to obtain and characterize the two ultrashort pulse lasers. Compensation signals for relative repetition frequency jitter and relative carrier envelope phase jitter of pulsed lasers, signals representing relative repetition frequency jitter are used for asynchronous sampling in the process of spectral detection, signals representing relative carrier envelope phase jitter are used for spectral interference signal mixing , and finally eliminate the influence of jitter in the signal processing stage to achieve high-precision spectral detection.

In the current adaptive dual-comb spectroscopy system, the source of the compensation signal comes from the mutual optical beat frequency of two narrow linewidth continuous lasers and two ultrashort pulse lasers. Due to environmental temperature and vibration changes, each narrow linewidth laser or The optical frequency of an ultrashort pulse laser will drift randomly with time. Therefore, the center frequency of the optical beat signal will also drift randomly with time, and the drift range is very large, which can easily exceed the bandwidth of the circuit filter, resulting in the loss of the beat signal. The circuit processing module fails, and the adaptive compensation system works abnormally. In order to control the drift range of optical beat frequency signals of narrow-linewidth CW lasers and ultrashort pulse lasers, a negative feedback loop can be established, and parameters such as the temperature of the CW laser, the pump power, or the repetition frequency of the pulsed laser can be adjusted to combine the two The beat frequency drift of the system is controlled within the bandwidth of the follow-up circuit filter, but this negative feedback compensation method will inevitably cause interference to the adaptive optical comb spectrum and reduce the measurement accuracy of the system.

In the adaptive dual-comb spectroscopy system of the prior art, the compensation signal extraction method must first use a narrow linewidth continuous laser and an ultrashort pulse laser to optically beat the frequency, and there is a major hidden danger of the loss of the beat frequency signal, which affects the stability of the long-term operation of the system ,reliability.

Contents of the invention

The purpose of the present invention is to provide a kind of self-adaptive dual-comb spectral compensation signal extraction method for the deficiencies in the prior art, adopt two independent Michelson interferometers to measure the frequency jitter of two ultrashort pulse lasers respectively, utilize time The method of domain delay and frequency domain selection extracts the signals representing the relative repetition frequency jitter and relative carrier envelope phase jitter of two pulsed lasers, and realizes the dual optical comb spectrum measurement without the repetition frequency or carrier envelope phase of the pulsed laser. Active control avoids the optical frequency drift of narrow-linewidth continuous light and ultrashort pulse laser in the traditional adaptive dual-comb spectral compensation signal extraction method, ensures the long-term stable existence of beat frequency signals, and better solves the problem of optical beat frequency signals. The problem of compensation signal loss caused by drift is simple, the operation is convenient, and the stability of the adaptive dual-comb spectral measurement system is greatly improved.

The object of the present invention is achieved like this: a kind of self-adaptive dual optical comb spectral compensation signal extraction method comprises ultrashort pulse laser, photodetector, electrical frequency doubling and filtering unit and dual optical comb spectral data processing unit, and its characteristic is Two independent Michelson interferometers are used to measure the frequency jitter of two ultrashort pulse lasers respectively, and then the output light of the two Michelson interferometers enters two optical beam splitters respectively, and the two optical beam splitters couple the output light to the Four optical filters, the filtered four optical signals are respectively detected by four photodetectors, each photodetector divides the detected optical signal into two outputs on average, and one output light passes through the electrical frequency doubling and filtering unit Afterwards, the output light of the other channel enters the first-stage frequency mixing and the second-stage frequency mixing in turn, and then the optical signal processed by the second-stage frequency mixing is connected to the dual-comb spectrum data processing unit as a compensation signal for adaptive dual-comb spectrum; Each of the photodetectors divides the detected optical signal into two outputs on average, and four photodetectors respectively detect and obtain four optical signals ①, ②, ③ and ④, and each optical signal is divided into two outputs on average. , the two optical signals ① and ② output by one of the two photodetectors respectively enter the first-stage frequency mixing after passing through two electrical frequency multiplication and filtering units, and the two optical signals ① and ② output by the other of the two photodetectors directly enter the First-stage frequency mixing; the two optical signals ③ and ④ output by the other two photodetectors pass through the other two electrical frequency multiplication and filtering units respectively and then enter another first-stage frequency mixing, and the other two optical signals output by the other two photodetectors ③ and ④ two optical signals directly enter another first-level frequency mixing respectively; two electrical frequency multiplication and filtering units in the four electrical frequency multiplication and filtering units perform (p-1) times on ① and ③ optical signals respectively The other two electrical frequency multiplication and filtering units perform p-fold frequency multiplication processing on the ② and ④ optical signals respectively, and respectively obtain ①×(p-1), ②×p, ③×(p-1) and ④×p four frequency-multiplied signals, put the frequency-multiplied ①×(p-1), ②×p and the unmultiplied ① and ② optical signals into the first-level mixing, and the first-level mixing will ① After ×(p-1) is mixed with the optical signals of ①, ②×p and ②, two mixed optical signals of ①-② and ②×p-①×(p-1) are obtained respectively; The ③×(p-1), ④×p and the unmultiplied ③, ④ optical signals enter another level of mixing, and another level of mixing combines ③×(p-1) with ③, ④×p After mixing with the optical signal of ④, two mixed optical signals of ③-④ and ④×p-③×(p-1) are obtained respectively, and then ①-②, ②×p-①×(p-1 ) two mixed optical signals and ③-④ and ④×p-③×(p-1) two mixed optical signals respectively enter the secondary frequency mixing, and after the secondary frequency mixing processing, respectively obtain (①- ②)-(③-④) and [②×p-①×(p-1)]-[④×p-③×(p-1)] are connected as compensation signals for adaptive dual-comb spectrum Dual-comb spectrum data processing unit; the compensation signals of the two adaptive dual-comb spectra are (nm) △ f _r and △ f ₀ +q △ f _r , wherein: △ f _r is two ultrashort pulse Δf ₀ is the relative carrier envelope phase jitter of two ultrashort pulse lasers; p, n and m are all positive integers.

The Michelson interferometer includes a beam splitter or a fiber coupler, two Faraday mirrors, a time-delay crystal or a time-delay fiber and a band-driven acousto-optic modulator, and the output light of the ultrashort pulse laser passes through the beam splitter or fiber The coupler is divided into two beams of light according to the power ratio of 1:1. One beam of light is directly reflected by the first Faraday reflector and returns to the beam splitter or fiber coupler. The other beam of light first passes through the delay crystal or delay fiber. After passing through the belt-driven acousto-optic modulator, and finally reflected by the second Faraday reflector, the belt-driven acousto-optic modulator and time-delay crystal or time-delay fiber return to the beam splitter or fiber coupler in turn, and the two reflected lights Combine a beam on the beam splitter or fiber coupler to output from the Michelson interferometer.

The optical beam splitter is a semi-transparent and semi-reflective mirror with a splitting ratio of 1:1 or a fiber optic coupler.

The optical filter is a narrow-band filter mirror, optical fiber grating or optical fiber filter that allows laser light of a specific wavelength to pass through and prevents laser light of other wavelengths from passing through.

Compared with the prior art, the present invention has the following advantages:

(1) The optical beat frequency of narrow-linewidth continuous lasers and continuous lasers and pulsed lasers is not required, so random jitter of optical beat frequency signals is avoided, and the stability and reliability of the adaptive dual optical comb spectral compensation system are improved.

⑵. Two independent Michelson interferometers are used to measure the frequency jitter of two ultrashort pulse lasers respectively, without interference between each other and low detection noise.

⑶. Using the frequency domain selection method, coherently detect the beat frequency signal of the pulse in two different frequency windows. By flexibly selecting the frequency interval and window size, the frequency domain noise can be reduced and the detection sensitivity can be improved.

⑷. An acousto-optic modulator with a drive is added to the Michelson interferometer to shift the center frequency of the beat frequency signal to the center frequency of the acousto-optic modulator to reduce the noise near zero frequency.

(5) There is no need to establish an additional negative feedback circuit to compensate the drift of the signal, and no electronic circuit noise will be introduced, and high-precision adaptive dual-comb spectroscopy can be realized.

⑹. Using two free-running pulse lasers and adaptive control technology can realize dual-comb spectrum measurement without active control of repetition frequency or carrier envelope phase of pulse lasers. The system is simple and easy to operate.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the structural representation of the embodiment of spatial structure;

Fig. 3 is the structural representation of the embodiment of optical fiber structure;

Fig. 4 is a schematic diagram of the specific application of the present invention.

detailed description

Referring to accompanying drawing 1, the present invention is made of two ultrashort pulse lasers 1, two Michelson interferometers 2, two optical beam splitters 3, four optical filters 4, four photodetectors 5, four electrical times Frequency and filter unit 6, two first-stage frequency mixers 7, one second-stage frequency mixer 8 and dual optical comb spectral data processing unit 9 form the optical path of two compensation signals, and the output light of the ultrashort pulse laser 1 is incident on Michael The Michelson interferometer 2, the longer interferometric arm of the Michelson interferometer 2 includes a band-driven acousto-optic modulator, the modulation frequency is fa, and the output light of the Michelson interferometer 2 passes through an optical beam splitter 3, respectively Coupled to two optical filters 4, two photodetectors 5 are used to measure the filtered optical signals respectively, and the detected signals are respectively recorded as ① and ②, and the signal ① can be expressed as 2f _a + △ (nf _r1 +f ₀₁ + 2f _a ), n is a positive integer, its center frequency is at 2fa, and the signal drift includes the repetition frequency drift △f _r1 of the ultrashort pulse laser 1, the carrier envelope phase drift △f ₀₁ and the driving frequency drift of the acousto-optic modulator △ f _a , ②The signal can be expressed as 2f _a +△(mf _r1 +f ₀₁ +2f _a ), m is a positive integer, its center frequency is at 2fa, and the signal drift includes repetition frequency drift of ultrashort pulse laser 1, carrier packet network phase drift and the drift of the drive frequency of the AOM; the output light of another ultrashort pulse laser 1 is incident on another Michelson interferometer 2, and the interference arm with a longer optical path in the other Michelson interferometer 2 contains a Acousto-optic modulator with drive, the modulation frequency is fb, the output light of another Michelson interferometer 2 is coupled to the other two optical filters 4 through another optical beam splitter 2, and the other two photodetectors are used 4Measure the filtered optical signals respectively, and the detected signals are recorded as ③ and ④ respectively. The ③ signal can be expressed as 2f _b + △(nf _r2 + f ₀₂ + 2f _b ), n is a positive integer, and its center frequency is at 2fb , the drift of the signal includes the repetition frequency drift △f _r2 of another ultrashort pulse laser 1, the carrier envelope phase drift △f ₀₂ and the driving frequency drift △f _b of the acousto-optic modulator, ④The signal can be expressed as 2f _b + △ (mf _r2 +f ₀₂ +2f _b ), m is a positive integer, its center frequency is at 2fb, and the drift of the signal includes the repetition frequency drift of another ultrashort pulse laser 1, the carrier envelope phase drift and the driving frequency of the acousto-optic modulator drift; the signal detected by each photodetector 5 is evenly divided into two paths, one path is not frequency multiplied, and the other path adopts electrical frequency multiplication and filtering unit 6 to perform frequency multiplication processing on the above-mentioned ①, ②, ③ and ④ signals respectively, Perform (p-1) times frequency multiplication processing on ① and ③ signals, p is a positive integer, and perform p times frequency multiplication processing on ② and ④ signals, after four electrical frequency multiplication and filtering units 6 obtain four frequency multiplications The signals are respectively ①×(p-1), ②×p, ③×(p-1) and ④×p; using two first-stage mixers 7, for the multiplied signal and the non-multiplied signal mix first frequency processing to obtain four first-stage mixed signals, respectively: ①-②=(nm)△f _r1 , ②×p-①×(p-1)=2f _a +△f ₀₁ +(pgm -pgn+n)△f _r1 +2△f _a 、③-④＝(nm)△f _r2 、④×p-③×(p-1)＝2f _b +△f ₀₂ +(pgm-pgn+n )△f _r2 +2△f _b ; use the second-stage mixing 8 to perform the second-stage mixing processing on the signal after the first-stage mixing, and obtain two signals after the second-stage mixing, respectively: (① -②)-③-④)＝(nm)△f _r 、[②×p-①×(p-1)]-[④×p-③×(p-1)]＝2(f _a -f _b )+△f ₀ +(pgm-pgn+n)△f _r +2△(f _a -f _b );△f ₀ +q△f _r , the above two signals are substantially equal to (nm)△f _r , △f ₀ +q△f _r , where n, m and q are positive integers, △fr _r is the relative repetition frequency jitter of the two ultrashort pulse lasers 1, △f ₀ is the jitter of the two ultrashort pulse lasers 1 Relative to the phase jitter of the carrier envelope, these two signals can be directly used as compensation signals for adaptive dual-comb spectroscopy. Wherein, the Michelson interferometer 2 includes a beam splitter or a fiber coupler, a first Faraday mirror, a second Faraday mirror, a time-delay crystal or a time-delay fiber, and a tape-driven acousto-optic modulator. The output light of the pulsed laser 1 passes through a beam splitter or a fiber coupler, and is divided into two beams of light at a power ratio of 1:1, and one beam of light is directly reflected back to the beam splitter or fiber coupler through the first Faraday reflector, The other beam of light first passes through the delay crystal or delay fiber, is reflected by the belt-driven acousto-optic modulator and the second Faraday mirror, and then passes through the belt-driven acousto-optic modulator and time-delay crystal or delay fiber in turn, and returns to the To the beam splitter or fiber coupler, the two beams of reflected light are synthesized on the beam splitter or fiber coupler and output from the Michelson interferometer 2.

The present invention will be further described below with an adaptive dual-comb spectral compensation signal extraction system with a spatial structure and an optical fiber structure.

Example 1

Referring to accompanying drawing 2, the present invention is by two pulsed lasers 11,12, two Michelson interferometers 21,22, two optical beam splitters 31,32, four optical filters 41,42,43,44, four photodetectors 51, 52, 53, 54, four electrical frequency doubling and filtering units 61, 62, 63, 64, two primary mixers 71, 72, a secondary mixer 8 and dual optical combs The spectral data processing unit 9 constitutes a space-structured adaptive dual-comb spectral compensation signal extraction system.

The output light of the ultrashort pulse laser 11 is incident on the Michelson interferometer 21, wherein the Michelson interferometer 21 is composed of a beam splitter 211, a first Faraday reflector 212, a second Faraday reflector 215, a time delay crystal 213 and It is composed of an acousto-optic modulator 214 driven by a belt, and the modulation frequency is fa. The output light of the ultrashort pulse laser 11 passes through the beam splitter 211 and is divided into two beams of light at a power ratio of 1:1. One beam of light is directly reflected back to the beam splitter 211 by the first Faraday reflector 212, and the other beam passes through the The time-delay crystal 213 and the AOM 214 driven by the belt are finally reflected by the second Faraday reflector 213, and then return to the beam splitter 211 after passing through the AOM 214 and the time-delay crystal 213 driven by the belt in turn. The reflected light is combined into one beam on the beam splitter 211 and output from the Michelson interferometer 21 .

The output light of another ultrashort pulse laser 12 is incident on another Michelson interferometer 22, wherein, another Michelson interferometer 22 is composed of a beam splitter 221, a first Faraday reflector 222, a second Faraday reflector 225 , time-delay crystal 223 and band-driven acousto-optic modulator 224, and the modulation frequency is fa. The output light of another ultrashort pulse laser 12 is divided into two beams of light by a power ratio of 1:1 through the beam splitter 221, and one beam of light is directly reflected back to the beam splitter 221 through the first Faraday reflector 222, and the other beam of light First pass through the time-delay crystal 223 and the belt-driven AOM 224, and finally reflect through the second Faraday reflector 225, then pass through the belt-driven AOM 224 and the time-delay crystal 223, and then return to the beam splitter 221, The two beams of reflected light are synthesized on the beam splitter 221 and output from another Michelson interferometer 22 .

The output light of the Michelson interferometer 21 is respectively coupled to an optical filter 41 and another optical filter 43 through an optical beam splitter 31, and two photodetectors 51, 53 are used to measure the filtered optical signals respectively, and detect The signals are denoted as ① and ② respectively, the signal ① can be expressed as 2f _a + △ (nf _r1 + f ₀₁ + 2f _a ), n is a positive integer, its center frequency is 2fa, and the drift of the signal includes the ultrashort pulse laser 11 Repetition frequency drift △f _r1 , carrier envelope phase drift △f ₀₁ and AOM driving frequency drift △f _a , signal ② can be expressed as 2f _a + △(mf _r1 +f ₀₁ +2f _a ), m is A positive integer whose center frequency is 2fa, and the signal drift includes the repetition frequency drift of the ultrashort pulse laser 11, the carrier envelope phase drift and the driving frequency drift of the acousto-optic modulator.

The output light of the other Michelson interferometer 22 is respectively coupled to the optical filter 42 and another optical filter 44 through the optical beam splitter 32, and two photodetectors 52, 54 are used to measure the filtered optical signals respectively, The detected signals are denoted as ③ and ④ respectively, and the signal ③ can be expressed as 2f _b + △ (nf _r2 + f ₀₂ + 2f _b ), n is a positive integer, and its center frequency is at 2fb. The drift of the signal includes the ultrashort pulse laser 21 repetition frequency drift △f _r2 , carrier envelope phase drift △f ₀₂ and AOM drive frequency drift △f _b , the signal ④ can be expressed as 2f _b + △(mf _r2 +f ₀₂ +2f _b ), m is a positive integer, its center frequency is 2fb, and the signal drift includes the repetition frequency drift of another ultrashort pulse laser 12, the carrier envelope phase drift and the drive frequency drift of the AOM.

Divide the ①, ②, ③ and ④ signals detected by the above four photodetectors 51, 52, 53, 54 into two paths on average for each signal, one path without frequency multiplication, and one path with four electrical frequency multiplication and filtering units 61, 62, 63, and 64 perform frequency multiplication processing on the above-mentioned ①, ②, ③ and ④ signals respectively, and perform (p-1) times frequency multiplication processing on the signals ① and ③, p is a positive integer, and perform frequency multiplication processing on the signals ② and ④ Perform p-fold frequency multiplication processing to obtain four multiplied signals, which are ①×(p-1), ②×p, ③×(p-1), ④×p; using two first-level mixing Devices 71 and 72 perform first-stage mixing processing on the multiplied signal and the non-multiplied signal to obtain four first-stage mixed signals, which are respectively: ①-②=(nm)△f _r1 , ②×p-①×(p-1)＝2f _a +△f ₀₁ +(pgm-pgn+n)△f _r1 +2△f _a 、③-④＝(nm)△f _r2 、④×p- ③×(p-1)=2f _b +△f ₀₂ +(pgm-pgn+n)△f _r2 +2△f _b ; a second-stage mixer 8 is used to make the first-stage mixed signal The second-stage frequency mixing process obtains two second-stage mixed signals, which are: (①-②)-(③-④)=(nm)△f _r , [②×p-①×(p -1)]-[④×p-③×(p-1)]＝2(f _a -f _b )+△f ₀ +(pgm-pgn+n)△f _r +2△(f _a -f _b ); △f ₀ +q△fr , the above two signals are substantially equal to (nm)△f _r , △f ₀ +q△f _r , where n, m, and q are positive integers, and _{△f r is} The relative repetition frequency jitter of the two ultrashort pulse lasers 11, 12, △ f ₀ is the relative carrier envelope phase jitter of the two ultrashort pulse lasers 11, 12, these two signals can be directly used as adaptive dual optical comb spectrum The compensation signal is connected to the dual-comb spectral data processing unit 9.

Example 2

Referring to accompanying drawing 3, the present invention is by two pulsed lasers 11,12, two Michelson interferometers 21,22, two optical beam splitters 31,32, four optical filters 41,42,43,45, four A photodetector 51, 52, 53, 54, four electrical frequency doubling and filtering units 61, 62, 63, 64, two primary mixers 71, 72 and a secondary mixer 8 and dual optical combs The spectral data processing unit 9 constitutes an extraction system of an adaptive dual-comb spectral compensation signal with a fiber structure.

The output light of the ultrashort pulse laser 11 is incident on the Michelson interferometer 21, wherein the Michelson interferometer consists of a fiber coupler 211, a first Faraday reflector 212, a second Faraday reflector 215, a time-delay fiber 213 and a ribbon The driven acousto-optic modulator 214 is composed of the modulation frequency fa. The output light of the pulsed laser 11 passes through the fiber coupler 211 and is divided into two beams of light according to a power ratio of 1:1. One beam of light is directly reflected back to the fiber coupler 211 by the first Faraday reflector 212, and the other beam of light is first delayed. The optical fiber 213 passes through the acousto-optic modulator 214 driven by the belt, and finally reflects through the second Faraday reflector 215, and then returns to the fiber coupler 211 through the acousto-optic modulator 214 driven by the belt and the time-delay optical fiber 213 in turn. The light is combined into one beam on the fiber coupler 211 and output from the Michelson interferometer 21 .

The output light of the Michelson interferometer 21 is respectively coupled to the optical filter 41 and the optical filter 43 through the optical beam splitter 31, and two photodetectors 51, 53 are used to measure the filtered optical signal respectively, and the detected signal Denoted as ① and ② respectively, the signal ① can be expressed as 2f _a + △ (nf _r1 + f ₀₁ + 2f _a ), n is a positive integer, its center frequency is 2fa, and the drift of the signal includes the repetition frequency of the ultrashort pulse laser 11 Drift △f _r1 , carrier envelope phase drift △f ₀₁ and AOM driving frequency drift △f _a , signal ② can be expressed as 2f _a + △(mf _r1 +f ₀₁ +2f _a ), m is a positive integer , its center frequency is at 2fa, and the drift of the signal includes the drift of the repetition frequency of the ultrashort pulse laser 11, the drift of the carrier envelope phase and the drift of the driving frequency of the acousto-optic modulator.

The output light of another ultrashort pulse laser 12 is incident on the Michelson interferometer 22, wherein the Michelson interferometer 22 is composed of a fiber coupler 221, a first Faraday reflector 222, a second Faraday reflector 225, a time-delay optical fiber 223 and the band-driven acousto-optic modulator 224, the modulation frequency is fb. The output light of another ultrashort pulse laser 12 is divided into two beams of light by a power ratio of 1:1 through the fiber coupler 221, and one beam of light is directly reflected back to the fiber coupler 221 through the first Faraday reflector 222, and the other beam of light First pass through the time-delay fiber 223, then pass through the belt-driven acousto-optic modulator 224, and finally reflect through the second Faraday mirror 225, and then return to the fiber coupler 221 through the belt-driven acousto-optic modulator 224 and time-delay fiber 223 , the two beams of reflected light are synthesized on the fiber coupler 221 and output from the Michelson interferometer 22 .

The output light of the other Michelson interferometer 22 is respectively coupled to the optical filter 42 and another optical filter 44 through the optical beam splitter 32, and two photodetectors 52, 54 are used to measure the filtered optical signals respectively, The detected signals are denoted as ③ and ④ respectively, and the signal ③ can be expressed as 2f _b + △ (nf _r2 + f ₀₂ + 2f _b ), n is a positive integer, and its center frequency is at 2fb. The drift of the signal includes the ultrashort pulse laser The repetition frequency drift △f _r2 of 12, the carrier envelope phase drift △f ₀₂ and the driving frequency drift △f _b of the AOM, the signal ④ can be expressed as 2f _b + △(mf _r2 +f ₀₂ +2f _b ), m is a positive integer, and its center frequency is 2fb. The signal drift includes the repetition frequency drift of the ultrashort pulse laser 12, the carrier envelope phase drift and the driving frequency drift of the acousto-optic modulator.

Divide the ①, ②, ③ and ④ signals detected by the above four photodetectors 51, 52, 53, 54 into two paths on average for each signal, one path without frequency multiplication, and one path with four electrical frequency multiplication and filtering units 61, 2, 63, and 64 perform frequency multiplication processing on the above-mentioned ①, ②, ③ and ④ signals respectively, and perform (p-1) times frequency multiplication processing on the signals ① and ③, p is a positive integer, and perform frequency multiplication processing on the signals ② and ④ Perform p-fold frequency multiplication processing to obtain four multiplied signals, which are ①×(p-1), ②×p, ③×(p-1), ④×p; using two first-level mixing Devices 71 and 72 perform first-stage mixing processing on the multiplied signal and the non-multiplied signal to obtain four first-stage mixed signals, which are respectively: ①-②=(nm)△f _r1 , ②×p-①×(p-1)＝2f _a +△f ₀₁ +(pgm-pgn+n)△f _r1 +2△f _a 、③-④＝(nm)△f _r2 、④×p- ③×(p-1)=2f _b +△f ₀₂ +(pgm-pgn+n)△f _r2 +2△f _b ; adopt a second-stage mixer 8 to make the first-stage mixed signal Second-level mixing processing, to obtain two second-level mixing signals, respectively: (①-②)-(③-④)=(nm)△f _r , [②×p-①×(p- 1)]-[④×p-③×(p-1)]＝2(f _a -f _b )+△f ₀ +(pgm-pgn+n)△f _r +2△(f _a -f _b ); △f ₀ +q△f _r , the above two signals are substantially equal to (nm)△f _r , △f ₀ +q△f _r , where n, m, q are positive integers, and △f _r is two The relative repetition frequency jitter of two ultrashort pulse lasers 11, 21, Δf ₀ is the relative carrier envelope phase jitter of two ultrashort pulse lasers 11, 21, these two signals can be directly used as the The compensation signal is connected to the dual-comb spectral data processing unit 9 .

Example 3

Referring to accompanying drawing 4, the present invention is made up of two pulsed lasers 11,12, sample pool 10, interference signal detection module 14, two Michelson interferometers 21,22, two optical beam splitters 31,32, four optical filter 41, 42, 43, 44, four photodetectors 51, 52, 53, 54, four electrical frequency multiplication and filtering units 61, 62, 63, 64, two primary mixers 71, 72, one It consists of a secondary mixer 8, an adaptive dual-comb spectral system data processing unit 9 and a spectral measurement result output module 13.

The output of the ultrashort pulse laser 11 is divided into two paths, one path is directly incident to the sample cell 10, and the other path is incident to the Michelson interferometer 21, wherein the Michelson interferometer is composed of a beam splitter 211, a first Faraday reflector 212 , a second Faraday reflector 215, a delay crystal 213 and a band-driven acousto-optic modulator 214, and the modulation frequency is fa. The output light of the ultrashort pulse laser 11 passes through the beam splitter 211 and is divided into two beams of light at a power ratio of 1:1. One beam of light is directly reflected back to the beam splitter 211 by the first Faraday reflector 212, and the other beam passes through the The time-delay crystal 213 passes through the acousto-optic modulator 214 driven by the belt, and finally is reflected by the second Faraday reflector 215, and then returns to the beam splitter 211 through the acousto-optic modulator 214 and the time-delay crystal 213 driven by the belt in turn. The beams of reflected light are combined into one beam on the beam splitter 211 and output from the Michelson interferometer 21 .

The output light of another ultrashort pulse laser 12 is incident on another Michelson interferometer 22, wherein, another Michelson interferometer 22 is composed of a beam splitter 221, a first Faraday reflector 222, a second Faraday reflector 225 , time-delay crystal 223 and band-driven acousto-optic modulator 224, and the modulation frequency is fb. The output light of another ultrashort pulse laser 21 is divided into two beams of light by a power ratio of 1:1 through the beam splitter 221, and one beam of light is directly reflected back to the beam splitter 221 through the first Faraday reflector 222, and the other beam of light First pass through the delay crystal 223, then pass through the belt-driven acousto-optic modulator 224, and finally reflect through the second Faraday mirror 225, and then return to the beam splitter 221 through the belt-driven acousto-optic modulator 224 and time-delay crystal 223 , the two beams of reflected light are synthesized on the beam splitter 221 and output from another Michelson interferometer 22 .

The output light of the Michelson interferometer 21 is respectively coupled to an optical filter 41 and another optical filter 43 through an optical beam splitter 31, and two photodetectors 51, 53 are used to measure the filtered optical signals respectively, and detect The signals are denoted as ① and ② respectively, the signal ① can be expressed as 2f _a + △ (nf _r1 + f ₀₁ + 2f _a ), n is a positive integer, its center frequency is 2fa, and the drift of the signal includes the ultrashort pulse laser 11 Repetition frequency drift △f _r1 , carrier envelope phase drift △f ₀₁ and AOM driving frequency drift △f _a , signal ② can be expressed as 2f _a + △(mf _r1 +f ₀₁ +2f _a ), m is A positive integer whose center frequency is 2fa, and the signal drift includes the repetition frequency drift of the ultrashort pulse laser 11, the carrier envelope phase drift and the driving frequency drift of the acousto-optic modulator.

The output light of the other Michelson interferometer 22 is respectively coupled to the optical filter 42 and another optical filter 44 through the optical beam splitter 32, and two photodetectors 52, 54 are used to measure the filtered optical signals respectively, The detected signals are denoted as ③ and ④ respectively, and the signal ③ can be expressed as 2f _b + △ (nf _r2 + f ₀₂ + 2f _b ), n is a positive integer, and its center frequency is at 2fb. The drift of the signal includes the ultrashort pulse laser 21 repetition frequency drift △f _r2 , carrier envelope phase drift △f ₀₂ and AOM drive frequency drift △f _b , the signal ④ can be expressed as 2f _b + △(mf _r2 +f ₀₂ +2f _b ), m is a positive integer, its center frequency is 2fb, and the signal drift includes the repetition frequency drift of another ultrashort pulse laser 12, the carrier envelope phase drift and the drive frequency drift of the AOM.

Divide the ①, ②, ③ and ④ signals detected by the above four photodetectors 51, 52, 53, 54 into two paths on average for each signal, one path without frequency multiplication, and one path with four electrical frequency multiplication and filtering units 61, 2, 63, and 64 perform frequency multiplication processing on the above-mentioned ①, ②, ③ and ④ signals respectively, and perform (p-1) times frequency multiplication processing on the signals ① and ③, p is a positive integer, and perform frequency multiplication processing on the signals ② and ④ Perform p-fold frequency multiplication processing to obtain four multiplied signals, which are ①×(p-1), ②×p, ③×(p-1), ④×p; using two first-level mixing Devices 71 and 72 perform first-stage mixing processing on the multiplied signal and the non-multiplied signal to obtain four first-stage mixed signals, which are respectively: ①-②=(nm)△f _r1 , ②×p-①×(p-1)＝2f _a +△f ₀₁ +(pgm-pgn+n)△f _r1 +2△f _a 、③-④＝(nm)△f _r2 、④×p- ③×(p-1)=2f _b +△f ₀₂ +(pgm-pgn+n)△f _r2 +2△f _b ; use the second-stage mixer 8 to perform the second First-stage frequency mixing processing to obtain two second-stage mixed signals, which are: (①-②)-(③-④)=(nm)△f _r , [②×p-①×(p-1 )]-[④×p-③×(p-1)]＝2(f _a -f _b )+△f ₀ +(pgm-pgn+n)△f _r +2△(f _a -f _b ) ; △f ₀ +q△f _r , the above two signals are substantially equal to (nm)△f _r , △f ₀ +q△f _r , where n, m, q are positive integers, and △f _r is two The relative repetition frequency jitter of the ultrashort pulse lasers 11 and 12, △ f ₀ is the relative carrier envelope phase jitter of the two ultrashort pulse lasers 11 and 12, these two signals can be directly used as compensation for the adaptive dual optical comb spectrum The signal is connected to the dual-comb spectral data processing unit 9.

The present invention measures the spectrum of the sample in this way: two beams of light from an ultrashort pulse laser 11 and another ultrashort pulse laser 12 are incident into the sample cell 10 to irradiate the sample to be measured, and then the two beams of incident light are combined into one beam and incident on the interferometer Signal detection module 14, the interference signal detection module 14 measures the interference signal of two ultrashort pulse lasers 11, 12, and the interference signal is input to the adaptive dual optical comb spectroscopy system data processing unit 9, and the adaptive dual optical comb spectroscopy system data The processing unit 9 has three input signals, and the three input signals are respectively characterized as the compensation signal of the two pulsed lasers 11 and 12 relative to the repetition frequency jitter, the compensation signal of the relative carrier envelope phase jitter, and the interference signal after passing through the sample cell 10, The data processing unit 9 of the adaptive dual-comb spectroscopy system adopts the compensation signal representing the relative repetition frequency jitter of the two pulsed lasers 11 and 12 as an asynchronous clock sampling signal, and adopts the signal representing the relative carrier envelope phase jitter of the two pulsed lasers 11 and 12 The compensation signal is mixed with the interference signal of the two pulsed lasers 11, 12 after passing through the sample cell 10, respectively eliminating the influence of the relative repetition frequency and relative carrier envelope phase jitter of the two pulsed lasers 11, 12 on the spectral measurement, and obtaining high The spectral measurement results with high precision are finally output by the spectral measurement result output module 13.

The above is only a further description of the present invention, and is not intended to limit the implementation and application of this patent. All equivalent implementations of the present invention should be included in the scope of claims of this patent.

Claims (4)

1. An adaptive double-comb spectral compensation signal extraction method, comprising ultrashort pulse laser, photodetector, electrical frequency doubling and filtering unit and dual-comb spectral data processing unit, is characterized in that two independent Michelson The interferometer measures the frequency jitter of two ultrashort pulse lasers respectively, and then the output light of the two Michelson interferometers enters two optical beam splitters respectively, and the two optical beam splitters respectively couple the output light to four optical filters for filtering The last four optical signals are respectively detected by four photodetectors, and each photodetector divides the detected optical signal into two outputs on average, and one output light passes through the electrical frequency doubling and filtering unit and is sequentially combined with the other output light Enter the first-level frequency mixing and the second-level frequency mixing respectively, and then the optical signal processed by the second-level frequency mixing is connected to the dual-comb spectrum data processing unit as the compensation signal of the adaptive dual-comb spectrum; each photodetector Divide the detected optical signal into two output channels on average and form four photodetectors to detect four optical signals ①, ②, ③ and ④ respectively. The two optical signals ① and ② enter the first-stage frequency mixing after passing through two electrical frequency multiplication and filtering units, and the two optical signals ① and ② output by the other channel of the two photodetectors directly enter the first-stage frequency mixing respectively; the other two The two optical signals ③ and ④ output by one photodetector pass through the other two electrical frequency doubling and filtering units respectively and then enter another first-stage frequency mixing, and the two optical signals ③ and ④ output by the other two photodetectors respectively Directly enter another first-level frequency mixing; two of the four electrical frequency multiplication and filter units perform (p-1) times frequency multiplication processing on ① and ③ optical signals respectively, and the other two An electrical frequency multiplication and filtering unit performs p times frequency multiplication processing on ② and ④ optical signals respectively, and obtains ①×(p-1), ②×p, ③×(p-1) and ④×p four times respectively After the frequency signal, the ①×(p-1), ②×p after frequency multiplication and the unmultiplied ① and ② optical signals enter the first-stage mixing, and the first-stage mixing combines ①×(p-1) and After the optical signals of ①, ②×p and ② are mixed, two mixed optical signals of ①-② and ②×p-①×(p-1) are obtained respectively; the multiplied ③×(p-1 ), ④×p and unmultiplied ③, ④ optical signals enter another first-stage mixing, and another first-stage mixing mixes ③×(p-1) with ③, ④×p and ④ optical signals Finally, two mixed optical signals of ③-④ and ④×p-③×(p-1) are obtained respectively, and then the two mixed-frequency optical signals of ①-②, ②×p-①×(p-1) The signal and ③-④ and ④×p-③×(p-1) mixed optical signals respectively enter the second stage of mixing, and after the second stage of mixing, (①-②)-(③-④ ) and [②×p-①×(p-1)]-[④×p-③×(p-1)] are two compensation signals of adaptive dual-comb spectrum connected to the dual-comb spectrum data processing unit ; The compensation signals of the two adaptive dual-comb spectra are respectively (nm) △ f _r and △ f ₀ +q △ f _r , where: △ f _r is the relative repetition frequency of the two ultrashort pulse lasers Δf ₀ is the relative carrier envelope phase jitter of two ultrashort pulse lasers; p, n and m are all positive integers. 2. according to claim 1 said adaptive dual-comb spectrum compensation signal extraction method, it is characterized in that said Michelson interferometer comprises beam splitter or fiber coupler, two Faraday reflectors, time-delay crystal or time-delay optical fiber And the belt-driven acousto-optic modulator, the output light of the ultrashort pulse laser is divided into two beams by a beam splitter or fiber coupler at a power ratio of 1:1, and one beam is directly reflected by the first Faraday reflector and returned to the Beam splitter or fiber optic coupler, the other beam first passes through the delay crystal or delay fiber, then passes through the belt-driven acousto-optic modulator, and finally is reflected by the second Faraday mirror, and then passes through the belt-driven acousto-optic modulator in turn And time-delay crystal or time-delay fiber back to beam splitter or fiber coupler, two beams of reflected light are synthesized on beam splitter or fiber coupler to output from Michelson interferometer. 3. according to claim 1 said adaptive dual-comb spectrum compensation signal extraction method, it is characterized in that said optical beam splitter is a semi-transparent and semi-reflective mirror or a fiber coupler with a split ratio of 1:1. 4. according to claim 1 said adaptive dual-comb spectrum compensation signal extraction method, it is characterized in that said optical filter is to allow the laser of specific wavelength to pass through, cut off the narrow-band filter optics, fiber grating or fiber filter that other wavelength lasers pass through device.