CN113281278A - Rapid ultrahigh-resolution transient absorption spectrum measuring device and measuring method - Google Patents
Rapid ultrahigh-resolution transient absorption spectrum measuring device and measuring method Download PDFInfo
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Abstract
The invention discloses a rapid ultrahigh-resolution transient absorption spectrum measuring device and a measuring method. The test device comprises: the mode-locked optical fiber optical comb system is used for generating pump light, detection light and local oscillator light; the optical power amplification unit is used for carrying out power amplification on optical pulses of pump light, detection light and local oscillator light output by the mode-locked optical fiber optical comb system; the nonlinear frequency conversion unit adopts a continuous spectrum technology to realize the generation of optical comb frequency which is continuously expanded in a wide spectrum range; the double asynchronous light sampling unit is used for sampling the pumping light and the detection light, the local oscillator light and the pumping light and the detection light which pass through the sample; the photoelectric detection unit is used for acquiring the intensity information of the interference signal; and the data acquisition and processing unit is used for completing acquisition and processing of interference signals through an electrical low-pass filter and a high-speed digital acquisition card. The invention can improve the transient spectrum signal acquisition speed.
Description
Technical Field
The invention relates to the technical field of transient absorption spectrum, in particular to a rapid ultrahigh-resolution transient absorption spectrum measuring device and a measuring method.
Background
Femtosecond pumping-detection is the most important time-resolved transient spectrum technology at present, can directly measure ultrafast physical processes such as excitation, relaxation, separation, transfer, diffusion, recombination and the like of electron hole pairs in materials under the excitation of optical energy or electric energy, provides important theoretical basis and guidance for the preparation of novel high-speed high-efficiency nano optoelectronic devices, and is also the key point for continuously discovering new phenomena and disclosing new mechanisms. The technical principle of femtosecond pumping-detection is as follows: one beam of ultrafast femtosecond laser with higher energy density is used as pumping light to change the physical state of the sample, and the other beam of ultrafast femtosecond laser with lower energy density and same source with the pumping light is used for detecting the physical state of the sample. Depending on the physical quantity of the material to be detected, the pump-detection technique can be implemented in various ways, such as absorption spectroscopy, fluorescence spectroscopy, etc. The transient absorption spectroscopy technique is the most classical one, and its basic working principle is: pumping light pulses are nearly vertically incident on a sample material to generate electronic transition from a ground state to an excited state energy level; the detection light enters the same region of the sample, and because the photoproduct excited by the pump light occupies part of the excited state energy level, the sample absorbs the detection light and correspondingly changes the transmissivity or reflectivity, and the evolution process of the particle number on the excited state energy level along with the time is detected at different delay time relative to the pump laser pulse. Generally, a femtosecond pump-probe system is composed of a femtosecond solid laser (providing pump pulses and probe pulses), a mechanical delay unit, a sample box, a photodetector, a lock-in amplifier, and the like. The time delay is realized by changing the optical path difference of the two beams. After the time delay sampling technology is introduced, the time resolution is determined by the width of two pulses and is irrelevant to the time constant of the detector, so that the femtosecond pumping-detection technology can research the transient characteristics of different spectral signals on a femtosecond scale and a picosecond scale. The transient absorption spectrum can be divided into a transmission type and a reflection type pumping-detection according to different detection light sources, wherein the former detects a detection spectrum transmitted through a sample, and the latter detects a spectrum after the detection light is reflected by the sample.
In essence, the amount of information provided by a spectrum depends on the frequency accuracy, time accuracy, and detection sensitivity that the spectrum can achieve. Meanwhile, the spectrum acquisition process is also limited by the measurement time of the system, which corresponds to the reciprocal of the working bandwidth. However, the conventional femtosecond pumping-detection has the following common technical problems: the frequency precision is poor. The resolving power of the dispersive spectral measurement instrument or the interference spectral measurement instrument is limited by the ratio of the maximum optical path difference to the laser wavelength, the frequency resolving value is usually larger than 1GHz, the resolving precision is difficult to improve, and the fine energy level structure of the material is difficult to observe; ② the measurement time is long. The acquisition speed of time-resolved spectral data is slowed due to the low working bandwidth (at the mHz level) of the mechanical delay unit, particularly, when a space-time-resolved two-dimensional scanning image of a material is acquired, the total measurement time even needs to be calculated according to the day, the long test time represents that the system puts forward higher requirements on the stability of a laser, and simultaneously, a tested sample is only limited to a photo-thermal stable sample; and detection sensitivity is low. Due to the adoption of the incoherent intensity detection method, the spectral detection sensitivity is not high, the measurement signal-to-noise ratio is low, the signal-to-noise ratio is generally required to be improved by adopting a phase-locked amplification technology, even if the signal-to-noise ratio is improved by a limited amount, the requirement on detecting weak spectral signals is difficult to meet, and meanwhile, the data acquisition speed is further slowed down due to the phase-locked amplifier. And fourthly, the amplitude spectrum and the phase spectrum cannot be measured simultaneously. The effect of the optical field on the material is simultaneously reflected on the real part and the imaginary part of the dielectric constant, however, a single intensity detection can only measure the absorption spectrum (imaginary part of the dielectric constant) of the material, and to measure the phase spectrum (real part of the dielectric constant), the reflection spectrum and the absorption spectrum of the material must be respectively measured, and the long-time stability of the light source and the material in the process of measuring in advance and in the process of measuring in the later period will face a great challenge, which will cause the deterioration of the signal quality. In addition, the traditional femtosecond solid laser also has the defects of high price, large volume, difficult maintenance and the like, and the system is only limited to scientific research in a high-end laboratory and cannot be popularized in a large range.
Optical frequency combs (optical combs for short) are the product of a combination of frequency stabilized laser based precision optical frequency measurements and femtosecond laser based ultrafast optics. The optical frequency comb is originally designed to provide a new measuring scheme for precise frequency measurement, and the research and application of the optical frequency comb gradually relate to the related field of spectroscopy along with the continuous development of the technology in recent years. 2019, T.W.
Professor writes a review article on Nature Photonics, a journal of optical top, to indicate that various optical comb spectrum technologies have become the leading edge of international research and hot spots, and the dual optical comb spectrum technology is undoubtedly the most revolutionary technical progress. The double-optical comb spectrum obtains spectrum information by carrying out Fourier transform on a multi-heterodyne interference signal between two beams of optical comb pulses, and is mainly characterized in that a mechanical delay unit is not needed for spectrum detection, the working bandwidth can reach the kHz level, and hundreds to thousands of times of spectrum detection can be finished within 1 s. In addition, the double-optical comb spectrum technology is the only wide spectrum technology which can obtain the comb tooth frequency resolution capability in the range from ultraviolet to mid-infrared spectrum at present, has the highest frequency precision (reaching dozens of MHz), and is suitable for the research of various atomic molecular dynamics. In the time domain, the spectrum of the double optical combs shows an asynchronous optical sampling process, the size of a detection time window is the same as the reciprocal of the repetition frequency of the optical combs, and as long as the repetition frequency difference of the two optical combs meets the Nyquist sampling theorem, the delay step length can be flexibly selected; in a frequency domain, the double-optical comb spectrum is represented by multi-heterodyne coherent detection, compared with an incoherent intensity detection method, the detection sensitivity is higher, and the detection capability of weak spectrum signals is more prominent.
On one hand, the traditional femtosecond pump-detection technology has many technical defects, new technical innovation is urgently needed, and a highly-deterministic optical comb is undoubtedly the best choice in the aspect of a light source; on the other hand, the optical comb light source itself has been applied to spectroscopy research, and the double optical comb spectroscopy technology, as the latest and most revolutionary spectroscopy technology, has irreplaceable advantages in terms of frequency accuracy, measurement time and sensitivity.
In 2016, the research group of professor k.minoshima in japan combines the double optical comb spectrum technique with the pump-detection technique, and proves an ultrafast time-resolved transient absorption spectrum measurement system in the near infrared band, which adopts two optical fiber optical comb light sources: one part of the optical comb is divided into pumping light, and the other part of the optical comb is used as detection light after mechanical delay; and the other optical comb with different repetition frequencies is used as local oscillator light to carry out multi-heterodyne coherent detection with the detection optical comb after passing through the material. The work researches transient complex absorption spectrum information (amplitude spectrum and phase spectrum can be obtained simultaneously by coherent detection) of semiconductor material indium gallium arsenic near the wavelength 1560nm, and emphasizes that the acquisition speed of the system is obviously improved after the introduction of the double-optical comb spectrum. Because the pumping optical comb and the detection optical comb are derived from the same optical comb and have the same repetition frequency, the system adopts a mechanical delay unit and has no advantage in time delay measurement indexes. In 2018, a transient absorption spectrum technology built by two solid optical comb light sources is reported by a Korean M.Cho professor research group, the transient absorption spectrum and the transient refractive index spectrum of liquid molecules can be measured simultaneously, and the technical advantages of the system in the aspects of test time, spectral range and frequency precision are proved. The work uses two beams of solid laser optical comb light sources with repetitive frequency differences. The difference is that the time delay between the pumping optical comb and the detecting optical comb is realized by the asynchronous optical sampling process generated by the repeated frequency difference of the two optical combs, and the interference process between the detecting optical comb and the intrinsic optical comb is realized by the mechanical delay unit.
It can be seen from the above technical background that the pumping-detection technology is combined with the optical comb spectrum technology, which can not only solve the technical limitation that the double optical comb spectrum technology cannot measure transient signals, but also overcome the defects of poor precision, long measurement time, low detection sensitivity and the like of the traditional pumping-detection frequency, and can simultaneously measure an amplitude spectrum and a phase spectrum. The capability advantage can push the transient absorption spectrum to develop towards faster and higher precision, and a plurality of new fields of view are provided for scientific research. However, two existing verification works are realized by two optical combs, and only one asynchronous optical sampling process exists between the two optical combs, so that the measurement of spectral resolution and time resolution cannot be completed simultaneously, and the system must still comprise a mechanical delay unit. The technical data shows that no design and report about a rapid ultrahigh-resolution transient absorption spectrum measuring device utilizing a three-beam high-coherence fiber optical comb light source system exists at present.
Disclosure of Invention
The invention aims to provide a rapid ultrahigh-resolution transient absorption spectrum measuring device and a measuring method, which are used for overcoming the defects in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a fast ultra-high resolution transient absorption spectrum measuring device comprises:
the mode-locked optical fiber optical comb system is used for generating pump light, detection light and local oscillator light;
the optical power amplification unit is used for carrying out power amplification on optical pulses of pump light, detection light and local oscillator light output by the mode-locked optical fiber optical comb system;
the nonlinear frequency conversion unit adopts a continuous spectrum technology to realize the generation of optical comb frequency which is continuously expanded in a wide spectrum range;
the double asynchronous light sampling unit is used for sampling the pumping light and the detection light, the local oscillator light and the pumping light and the detection light which pass through the sample;
the photoelectric detection unit is used for acquiring the intensity information of the interference signal;
the data acquisition and processing unit finishes interference signal acquisition through an electrical low-pass filter and a high-speed digital acquisition card and calls a computer program to process the acquired interference signal;
the mode locking optical fiber optical comb system, the optical power amplification unit, the nonlinear frequency conversion unit, the double asynchronous optical sampling unit, the photoelectric detection unit and the data acquisition and processing unit are sequentially connected.
Furthermore, the mode-locked fiber optical comb system comprises three optical comb systems with the same structure, namely a pumping optical comb, a detecting optical comb and a local oscillator optical comb, wherein the optical comb system structure comprises an atomic clock and a single-frequency laser, the atomic clock is connected with the single-frequency laser and used for locking carrier envelope frequency shifts of three optical combs simultaneously, and the single-frequency laser is used as an optical frequency scale of the optical comb to lock repetition frequency.
Furthermore, the repetition frequency output by the single-frequency laser is 100MHz, and the output spectral range is 1560 +/-20 nm.
Furthermore, the single-frequency laser adopts a frequency locking of a PDH frequency stabilization system, and the PDH frequency stabilization system comprises an ultrastable single-frequency laser, an ultrastable F-P cavity and a photoelectric detector.
Further, the optical power amplification unit comprises three groups of erbium-doped fiber amplifiers respectively connected with the pumping optical comb, the detecting optical comb and the local oscillation optical comb, and the nonlinear frequency conversion unit comprises three groups of nonlinear frequency converters independently connected with the erbium-doped fiber amplifiers.
Further, the spectral range after the frequency conversion of the nonlinear frequency converter is 400-2500 nm.
Further, the double asynchronous light sampling unit comprises a first light reflector, a microscope system, a first polarization beam combiner, a second reflector, a second polarization beam combiner, a third light reflector, a fourth light reflector and a third polarization beam splitter, the first light reflector is used for reflecting the pump light, the third polarization beam splitter is used for dividing the detection light into a signal light path and a reference light path, the fourth light reflector and the third light reflector are used for reflecting the reference light path of the detection light in sequence, the microscope system is used for transmitting the signal light path and the pumping light, the first polarization beam combiner is used for combining the transmission signal light transmitted by the microscope system and the reference light path reflected by the third light reflecting mirror, the second reflector is used for reflecting the combined light passing through the first polarization beam combiner, and the second polarization beam combiner is used for combining the combined light reflected by the second reflector and the local oscillator light.
Further, the photoelectric detection unit comprises a diaphragm, a lens and a single-point high-speed detector which are sequentially arranged, the diaphragm is used for light path collimation and light beam convergence, the lens is used for focusing the light beam to the single-point high-speed detector, and the single-point high-speed detector is used for collecting interference signals.
The invention provides a measuring method of the rapid ultrahigh resolution transient absorption spectrum measuring device, which comprises the following steps,
s1, generating pump light, probe light and local oscillator light by the mode-locked fiber optical comb system;
s2, the optical power amplification unit performs power amplification on the optical pulses of the pump light, the detection light and the local oscillator light output by the mode-locked optical fiber optical comb system;
s3, the nonlinear frequency conversion unit adopts a super-continuum spectrum technology to realize the generation of optical comb frequency continuously expanded in a wide spectrum range;
s4, the double asynchronous light sampling unit samples the pumping light and the detecting light, the local oscillator light and the pumping light and the detecting light which pass through the sample;
s5, the photoelectric detection unit collects the intensity information of the interference signal;
and S6, the data acquisition and processing unit finishes acquisition of interference signals through an electric low-pass filter and a high-speed digital acquisition card, and the acquired interference signals are processed by calling a computer program to obtain index data of the three-optical-comb transient absorption spectrum experimental system.
Compared with the prior art, the invention upgrades the laser light source in the pumping-detecting system into the three-beam optical comb light source with high stability and high coherence, and has the advantages that:
1. the invention realizes complete mechanical delay-free sampling between pumping and detection and between detection and local oscillation, and can improve the acquisition speed of transient spectrum signals;
2. the transient absorption spectrum signal is obtained in a coherent detection process, so that the spectrum signal-to-noise ratio is obviously improved;
3. the time step length of the spectrum signal measured by the invention can be flexibly and rapidly adjusted by controlling the repeated frequency difference of the pumping optical comb and the detecting optical comb.
By combining the advantages, the invention can realize high-precision rapid measurement of the ultrafast time resolution amplitude spectrum and the phase spectrum with space resolution capability and wide spectrum range, and supports rapid high-precision transient absorption spectrum research of the short-stable material.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a block diagram of a fast ultra-high resolution transient absorption spectrum measuring device using a three-beam high-coherence optical comb light source system according to the present invention.
FIG. 2 is a schematic diagram of a fast ultra-high resolution transient absorption spectrum measuring device of a three-optical comb light source system according to the present invention.
In the figure: the system comprises a mode-locked fiber optical comb system 100, an atomic clock 101, a single-frequency laser 102, a pumping optical comb 103, a detection optical comb 104, a local oscillation optical comb 105, an optical power amplification unit 200, an erbium-doped fiber amplifier 201, a nonlinear frequency conversion unit 300, a nonlinear frequency converter 301, a double asynchronous optical sampling unit 400, a first optical reflector 401, a microscope system 402, a first polarization beam combiner 403, a second reflector 404, a second polarization beam combiner 405, a third optical reflector 406, a fourth optical reflector 407, a third polarization beam splitter 408, a photoelectric detection unit 500, a diaphragm 501, a lens 502, a single-point high-speed detector 503 and a data acquisition and processing unit 600.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the scope of the present invention will be more clearly and clearly defined.
Referring to fig. 1 and fig. 2, the present embodiment discloses a fast ultra-high resolution transient absorption spectrum measuring apparatus, including: a mode-locked fiber optical comb system 100 for generating pump light, probe light and local oscillator light; an optical power amplifying unit 200, configured to perform power amplification on optical pulses of the pump light, the probe light, and the local oscillator light output by the mode-locked optical fiber optical comb system 100; the nonlinear frequency conversion unit 300 is used for generating the optical comb frequency which is continuously expanded in a wide spectrum range by adopting a super-continuum spectrum technology; a double asynchronous optical sampling unit 400 for performing double asynchronous optical sampling of the pump light and the probe light, the local oscillator light and the pump light and the probe light passing through the sample; a photoelectric detection unit 500 for collecting intensity information of the interference signal; the data acquisition and processing unit 600 completes acquisition of interference signals through an electrical low-pass filter and a high-speed digital acquisition card, and calls a computer program to process the acquired interference signals, and the mode-locked fiber optical comb system 100, the optical power amplification unit 200, the nonlinear frequency conversion unit 300, the double asynchronous optical sampling unit 400, the photoelectric detection unit 500 and the data acquisition and processing unit 600 are sequentially connected.
The mode-locked fiber optical comb system 100 is a polarization-maintaining fiber mode-locked laser based on a nonlinear amplification ring mirror mechanism. An equivalent saturable absorption effect is generated by an interference method, so that the risk of photo-induced damage is eliminated; the mode-locked optical fiber comb system 100 comprises three optical comb system pumping optical combs 103, detection optical combs 104 and local oscillator optical combs 105 which are identical in structure, the optical comb system structure comprises an atomic clock 101 and a single-frequency laser 102, the atomic clock 101 is connected with the single-frequency laser 102, the output repetition frequency of the single-frequency laser 102 is 100MHz, and the output spectral range is 1560 +/-20 nm.
And the reference frequency scale is used for measuring the femtosecond laser pulse repetition frequency and the carrier envelope frequency shift of the mode-locked optical comb light source and controlling the circuit servo feedback.
Measuring the repetition frequency and the carrier envelope frequency shift of the femtosecond laser pulse, generating a supercontinuum with more than one octave by adopting a high nonlinear optical fiber, and measuring the carrier envelope frequency shift by frequency doubling and f-2f interference technologies; the repetition frequency is measured by using a hyperstable single-frequency laser and a beat frequency signal of an adjacent optical comb tooth. The precise control of the repetition frequency and the carrier envelope frequency shift is realized by controlling the intra-cavity electro-optical modulator and the pump light driving current.
The atomic clock 101 is used to lock the carrier envelope frequency shifts of the three-way optical comb simultaneously. The single-frequency laser 102 adopts a PDH frequency stabilization system to lock frequency, which is used as an optical frequency scale for three optical combs to lock repetition frequency. The PDH frequency stabilization system mainly comprises an ultrastable single-frequency laser, an ultrastable F-P cavity and a photoelectric detector. In a PDH frequency stabilization system, a multichannel frequency synthesizer is used as an oscillation source and aims to output a signal with a specific frequency for optical comb stabilization.
The optical power amplification unit 200 includes three sets of erbium-doped fiber amplifiers 201 respectively connected to the pump optical comb 103, the detection optical comb 104, and the local oscillator optical comb 105, where the erbium-doped fiber amplifiers 201 are used to amplify the power of the pulse output by the mode-locked fiber optical comb light source.
The nonlinear frequency conversion unit 300 comprises an erbium-doped fiber amplifier 201The spectrum range after the frequency conversion of the nonlinear frequency converter 301 is 400-2500nm, and for the requirements of optical combs of separated special spectrum bands such as visible light and intermediate infrared bands, a proper nonlinear crystal is designed and processed and is realized through a sum frequency, difference frequency and other nonlinear frequency conversion schemes; for the frequency components of the generated optical comb, the coherence of the optical comb after frequency conversion is researched by adopting a cross-correlation analysis method, and the phase noise of the optical comb is measured and analyzed through beat frequency.
The double asynchronous light sampling unit 400 comprises a first light reflector 401, a microscope system 402, a first polarization beam combiner 403, a second reflector 404, a second polarization beam combiner 405, a third light reflector 406, a fourth light reflector 407, a third polarization beam splitter 408, the first optical reflector 401 is used to reflect the pump light, the third polarization beam splitter 408 is used to split the probe light into a signal optical path and a reference optical path, the fourth optical reflector 407 and the third optical reflector 406 are used to reflect the reference optical path of the probe light sequentially, the microscope system 402 is used for transmitting a signal light path and a pump light, the first polarization beam combiner 403 is used for combining the transmitted signal light transmitted by the microscope system 402 and the reference light path reflected by the third light reflector 406, the second mirror 404 is used to reflect the combined light passing through the first polarization beam combiner 403, the second polarization beam combiner 405 is configured to combine the combined light reflected by the second mirror 404 with the local oscillator light.
In particular use of the double asynchronous optical sampling unit 400, the pump optical comb is reflected by the first optical mirror 401; the detection optical comb is divided into a signal optical path and a reference optical path by a third polarization beam splitter 408, and a fourth optical mirror 407 and a third optical mirror 406 are used for reflecting the reference optical path of the detection optical comb. Wherein the signal optical path and the pumping optical comb pass through the microscope system 402, and the transient spectrum loading is realized by the focusing effect of the microscope system 402 on the micro-area material. The collected transmitted signal light after passing through the material and the reference light reflected twice by the reflecting mirror are combined by the first polarization beam combiner 403, the second reflecting mirror 404 is used for reflecting the combined light of the pumping optical comb and the detection optical comb carrying the sample information, and the combined light and the local oscillator optical comb are combined at the second polarization beam combiner 405.
The material steady state absorption spectrum and transient absorption spectrum settings performed by the double asynchronous optical sampling unit 400 are described as follows: in the asynchronous optical sampling unit 400, the spectral information is obtained by fourier transforming the interference signal collected by the detector. Setting the repetition frequency of the pumping optical comb and the repetition frequency of the detecting optical comb to be the same value, controlling the delay amount through the phase interlocking device, and carrying out Fourier transform on interference signals of the local oscillator optical comb and the detecting optical comb to obtain the steady-state absorption spectrum of the material under the fixed delay amount. The repeated frequency difference between the pumping optical comb and the detecting optical comb is introduced into the asynchronous optical sampling unit 400, a double asynchronous optical sampling process among the pumping, detecting and local oscillation optical combs is formed, and a double asynchronous optical sampling path is planned by adjusting the difference value of the two repeated frequencies. And compiling a corresponding data processing program, calculating to obtain absorption spectrum information under different pumping-detection delay conditions, and obtaining the transient absorption spectrum of the space single point through two-dimensional drawing. And carrying out coherent average processing on the multiple interference images to improve the signal-to-noise ratio of the transient absorption spectrum. The space scanning of the micro-area material is realized by controlling the displacement mechanism of the material box in the microscope system. And finally obtaining key indexes of the three-optical-comb transient absorption spectrum experimental system, such as single-point measurement time, total measurement time, time resolution, frequency resolution, space resolution and the like.
The photoelectric detection unit 500 comprises a diaphragm 501, a lens 502 and a single-point high-speed detector 503 which are sequentially arranged, wherein the diaphragm 501 is used for collimating and converging light beams in a light path, the lens 502 is used for focusing the light beams to the single-point high-speed detector 503, and the single-point high-speed detector 503 is used for collecting interference signals.
The invention provides a measuring method of the rapid ultrahigh resolution transient absorption spectrum measuring device, which comprises the following steps,
step S1, the mode-locked fiber optical comb system 100 generates a pumping optical comb, a detecting optical comb and a local oscillator optical comb;
step S2, the optical power amplification unit 200 performs power amplification on the optical pulses of the pump light, the probe light, and the local oscillator light output by the mode-locked optical fiber comb system 100;
step S3, the nonlinear frequency conversion unit 300 adopts the super-continuum spectrum technology to realize the generation of the optical comb frequency which is continuously expanded in the wide spectrum range;
step S4, the double asynchronous optical sampling unit 400 performs double asynchronous optical sampling of the pump light and the probe light, the local oscillator light, and the pump light and the probe light passing through the sample;
step S5, the photoelectric detection unit 500 collects intensity information of the interference signal;
and step S6, the data acquisition and processing unit 600 finishes the acquisition of interference signals through an electric low-pass filter and a high-speed digital acquisition card, and calls a computer program to process the acquired interference signals to obtain index data of the three-optical-comb transient absorption spectrum experimental system.
Compared with the existing transient absorption spectrum technology, the invention has the beneficial effects that:
according to the invention, by utilizing a double asynchronous optical sampling process among the three beam optical combs, complete mechanical delay-free sampling among pumping, detection and local oscillation is realized, the transient spectrum signal acquisition speed can be improved, and the acquisition time of a single transient absorption spectrum signal diagram is less than 1 s; the detection of the transient absorption spectrum signal is a coherent detection process, and the average measurement of more than 1000s can be executed, so that the signal-to-noise ratio of the spectrum is obviously improved; the frequency resolution precision of the measured spectrum signal is the same as the repetition frequency of the optical comb, and can reach 100MHz level; the time step length of the measured spectrum signal can be flexibly adjusted by adjusting the repeated frequency difference of the pumping optical comb and the detection optical comb, and the adjustment speed is high and the definition is flexible; the invention can realize the spectral signal measurement of space-time resolution, and the minimum space resolution precision is less than 2 mu m; the wavelength range of the spectral signal which can be realized by using the quartz fiber laser device is 400-2500 nm;
although the embodiments of the present invention have been described with reference to the accompanying drawings, various changes or modifications may be made by the patentees within the scope of the appended claims, and within the scope of the invention, as long as they do not exceed the scope of the invention described in the claims.
Claims (9)
1. A fast ultra-high resolution transient absorption spectroscopy device, comprising:
the mode-locked optical fiber optical comb system is used for generating pump light, detection light and local oscillator light;
the optical power amplification unit is used for carrying out power amplification on optical pulses of pump light, detection light and local oscillator light output by the mode-locked optical fiber optical comb system;
the nonlinear frequency conversion unit adopts a continuous spectrum technology to realize the generation of optical comb frequency which is continuously expanded in a wide spectrum range;
the double asynchronous light sampling unit is used for sampling the pumping light and the detection light, the local oscillator light and the pumping light and the detection light which pass through the sample;
the photoelectric detection unit is used for acquiring the intensity information of the interference signal;
the data acquisition and processing unit finishes interference signal acquisition through an electrical low-pass filter and a high-speed digital acquisition card and calls a computer program to process the acquired interference signal;
the mode locking optical fiber optical comb system, the optical power amplification unit, the nonlinear frequency conversion unit, the double asynchronous optical sampling unit, the photoelectric detection unit and the data acquisition and processing unit are sequentially connected.
2. The apparatus of claim 1, wherein the mode-locked fiber comb system comprises three optical comb systems having the same structure, namely a pump optical comb, a probe optical comb and a local oscillator optical comb, the optical comb system structure comprises an atomic clock and a single-frequency laser, the atomic clock is connected to the single-frequency laser for simultaneously locking carrier envelope frequency shifts of the three optical combs, and the single-frequency laser is used as an optical frequency scale of the optical comb to lock a repetition frequency.
3. The apparatus according to claim 2, wherein the single-frequency laser outputs a repetition frequency of 100MHz and an output spectral range of 1560 ± 20 nm.
4. The fast ultra-high resolution transient absorption spectroscopy device of claim 2, wherein the single-frequency laser employs a PDH frequency stabilization system frequency lock, the PDH frequency stabilization system comprising an ultrastable single-frequency laser, an ultrastable F-P cavity, and a photodetector.
5. The apparatus according to claim 2, wherein the optical power amplifying unit comprises three sets of erbium-doped fiber amplifiers respectively connected to the pumping optical comb, the detecting optical comb and the local oscillator optical comb, and the nonlinear frequency conversion unit comprises three sets of nonlinear frequency converters independently connected to the erbium-doped fiber amplifiers.
6. The apparatus as claimed in claim 4, wherein the spectrum range of the nonlinear frequency converter after frequency conversion is 400-2500 nm.
7. The apparatus according to claim 2, wherein the double asynchronous light sampling unit comprises a first light reflector for reflecting the pump light, a microscope system, a first polarization beam combiner, a second reflector, a second polarization beam combiner, a third light reflector, a fourth light reflector, and a third polarization beam splitter for splitting the probe light into the signal light path and the reference light path, a fourth light reflector and a third light reflector for sequentially reflecting the reference light path of the probe light, a microscope system for transmitting the signal light path and the pump light, a first polarization beam combiner for combining the transmitted signal light transmitted by the microscope system and the reference light path reflected by the third light reflector, and a second reflector for reflecting the combined light passed by the first polarization beam combiner, and the second polarization beam combiner is used for combining the combined beam light reflected by the second reflecting mirror and the local oscillator light.
8. The fast ultra-high resolution transient absorption spectrum measuring device according to claim 2, wherein the photoelectric detection unit comprises a diaphragm, a lens and a single-point high-speed detector which are arranged in sequence, the diaphragm is used for collimating and converging light beams on an optical path, the lens is used for focusing the light beams to the single-point high-speed detector, and the single-point high-speed detector is used for collecting interference signals.
9. A measuring method of the fast ultra-high resolution transient absorption spectrum measuring device according to any one of claims 1 to 8, characterized by comprising the steps of,
s1, the mode-locked optical fiber optical comb system generates a pumping optical comb, a detection optical comb and a local oscillator optical comb;
s2, the optical power amplification unit performs power amplification on the optical pulses of the pump light, the detection light and the local oscillator light output by the mode-locked optical fiber optical comb system;
s3, the nonlinear frequency conversion unit adopts a super-continuum spectrum technology to realize the generation of optical comb frequency continuously expanded in a wide spectrum range;
s4, the double asynchronous light sampling unit samples the pumping light and the detecting light, the local oscillator light and the pumping light and the detecting light which pass through the sample;
s5, the photoelectric detection unit collects the intensity information of the interference signal;
and S6, the data acquisition and processing unit finishes acquisition of interference signals through an electric low-pass filter and a high-speed digital acquisition card, and the acquired interference signals are processed by calling a computer program to obtain index data of the three-optical-comb transient absorption spectrum experimental system.
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| CN117907277A (en) * | 2024-03-07 | 2024-04-19 | 南京信息工程大学 | Polarization enhancement type gas identification detection method and device based on deep learning |
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