Mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system

Abstract

The present invention discloses a mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system. The measurement system comprises a first high repetition rate mid-infrared light comb, a second high repetition rate mid-infrared light comb, an acousto-optic deflector, a sample cell, a high-speed detector, a two-dimensional single-shot scanning signal decoding module and a spectrum restoration module. The present invention uses a mid-infrared mode-locked laser with a repetition rate greater than 1 GHz as a light source, and adds a two-dimensional single-shot acousto-optic deflector (2D‑AOD) technology on the basis of a dual-comb. The acousto-optic deflection effect is used to realize real-time two-dimensional spectral detection of the sample, and two-dimensional spectral or image information is obtained by decoding, so as to achieve the purpose of high-speed and high-precision spectral measurement. The present invention has a wide range of applications in the fields of sample high-speed imaging, spectral detection, ultrafast measurement, etc.

Description

Technical Field

[0001] The present invention relates to the field of ultrafast spectral measurement, and in particular to a mid-infrared high repetition rate dual-optical comb ultrafast two-dimensional single-shot coherent measurement system. Background Art

[0002] The essence of an optical frequency comb (hereinafter referred to as "optical comb") is a series of highly stable mode-locked pulse sequences. By locking the frequency and phase of the mode-locked pulses, the stability of the pulse sequence can reach the same order of magnitude as an atomic clock. As a precise and stable frequency ruler, optical combs have always played an important role in the field of imaging and measurement. By linking microwave frequencies with optical frequencies, optical combs can easily achieve the accuracy of distance measurement at the nanometer level and the accuracy of time measurement at femtoseconds or even attoseconds.

[0003] The dual-comb measurement system is based on the optical comb, using the high propagation speed of the pulse and the high coherence of the optical comb to achieve the purpose of fast and precise sampling and real-time measurement. Compared with the traditional Fourier transform system, the dual-comb system has higher stability and sampling rate because the mechanical scanning required by the latter is eliminated. Taking the Fourier transform spectrometer as an example, the resolution of the traditional Fourier transform spectrometer is at most tens of megahertz (Jacquet, Patrick, et al. "Frequencycomb Fourier transform spectroscopy with kHz optical resolution." FourierTransform Spectroscopy. Optical Society of America, 2009), while the dual-comb spectrometer can easily reach the kilohertz level, and the accuracy is nearly four orders of magnitude higher than the former.

[0004] The current dual-comb measurement system is still limited to the point-by-point spatial scanning stage, and has not been able to fully utilize the rapid measurement advantages of the dual-comb system itself. The present invention uses a high-repetition-rate mid-infrared mode-locked laser as the light source, and adds two-dimensional single-shot acousto-optic deflection technology (2D-AOD) on the basis of the dual-comb. The acousto-optic deflection effect is used to achieve two-dimensional frequency encoding, and a two-dimensional single-shot excitation scan is performed on the sample. The two-dimensional spectrum or image information of the sample is obtained by decoding, thereby achieving the purpose of high-speed and high-precision imaging measurement. Summary of the invention

[0005] The present invention uses a high repetition rate mid-infrared mode-locked laser as a light comb source, adds a two-dimensional single-shot excitation scanning acousto-optic deflection technology to a traditional dual-comb system, and directly obtains real-time two-dimensional spectral information of the sample through debugging and decoding of a two-dimensional coded light beam.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] Mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system, including a first high repetition rate mid-infrared light comb, a second high repetition rate mid-infrared light comb, an acousto-optic deflector, a sample cell, a high-speed detector, a two-dimensional single-shot scanning signal decoding module and a spectrum restoration module;

[0008] Among them, the mode-locked pulse signals output by the first high repetition rate mid-infrared light comb and the second high repetition rate mid-infrared light comb are simultaneously input into the acousto-optic deflector to generate a frequency-coded two-dimensional laser beam array with low third-order intermodulation distortion; the optical signal output by the acousto-optic deflector is divided into two paths, one path is input into the sample pool to obtain the two-dimensional spectral signal of the sample, and the other path is used as a reference signal, which is spatially overlapped with the two-dimensional spectral signal of the sample after passing through the delayed optical path for interference, and then the coherent signal is collected by a high-speed detector, and the two-dimensional single-shot excitation coherent signal is modulated and decoded using a two-dimensional single-shot scanning signal decoding module, and finally the decoded signal is restored to a two-dimensional spectral image through a spectral restoration module.

[0009] Furthermore, the repetition rate of the second high repetition rate mid-infrared light comb of the first high repetition rate mid-infrared light comb is locked to two stable frequency reference sources; wherein the repetition rate of the first high repetition rate mid-infrared light comb is f The second highest repetition rate mid-infrared comb has a repetition rate of f+Df , then the frequency difference between the two optical combs is Df Much smaller than the repetition frequency of ultrashort pulses, Df <1MHz, f >1GHz.

[0010] Furthermore, the acousto-optic deflector is a two-dimensional single-shot scanning acousto-optic deflector (2D-AOD).

[0011] Furthermore, a two-dimensional laser beam array is input into the sample cell to perform a two-dimensional single excitation scan on the sample to obtain a two-dimensional spectral signal of the sample.

[0012] Compared with the prior art, the advantages of the present invention are:

[0013] The core components of the present invention are a two-dimensional single-shot excitation scanning acousto-optic deflector and a high-repetition-rate mid-infrared optical comb. The high-repetition-rate mid-infrared dual optical comb makes high-precision mid-infrared spectroscopy measurement possible, and the two-dimensional single-shot excitation scanning acousto-optic deflection technology enables high-speed two-dimensional scanning of samples. The present invention can be applied in the fields of ultrafast measurement, ultrafast imaging, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1Schematic diagram of the structure of the mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system in an embodiment of the present invention.

[0015] Figure 2 Schematic diagram of the two-dimensional single-shot scanning acousto-optic deflection technology in an embodiment of the present invention.

[0016] Figure 3 Schematic diagram of the optical path in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the specific implementation of the present invention is described in detail below with reference to the accompanying drawings and examples.

[0018] Example:

[0019] Mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system, such as Figure 1 As shown, it includes a first high repetition rate mid-infrared light comb 1-1, a second high repetition rate mid-infrared light comb 1-2, an acousto-optic deflector 1-3, a sample pool 1-4, a high-speed detector 1-5, a two-dimensional single excitation scanning signal decoding module 1-6 and a spectrum restoration module 1-7;

[0020] Among them, the mode-locked pulse signals output by the first high repetition rate mid-infrared light comb 1-1 and the second high repetition rate mid-infrared light comb 1-2 are simultaneously input into the acousto-optic deflector 1-3 to generate a frequency-coded two-dimensional laser beam array with low third-order intermodulation distortion; the optical signal output by the acousto-optic deflector 1-3 is divided into two paths, one path is input into the sample pool 1-4 to obtain the two-dimensional spectral signal of the sample, and the other path is used as a reference signal, which is spatially overlapped with the two-dimensional spectral signal of the sample after passing through the delayed optical path for interference, and then the coherent signal is collected by the high-speed detector 1-5, and the coherent signal of the two-dimensional single excitation scanning signal decoding module is used to modulate and decode the coherent signal of the two-dimensional single excitation, and finally the decoded signal is restored to a two-dimensional spectral image through the spectral restoration module 1-7.

[0021] The repetition rate of the second high repetition rate mid-infrared light comb 1-2 of the first high repetition rate mid-infrared light comb 1-1 is locked to two stable frequency reference sources; wherein the repetition rate of the first high repetition rate mid-infrared light comb 1-1 is f The repetition rate of the second highest repetition rate mid-infrared comb 1-2 is f+Df , then the frequency difference between the two optical combs is Df Much smaller than the repetition frequency of ultrashort pulses, Df <10MHz, f >1GHz.

[0022] The acousto-optic deflector 1-3 is a two-dimensional single-shot scanning acousto-optic deflector (2D-AOD). Figure 2 Schematic diagram of 2D-AOD.

[0023] A two-dimensional laser beam array is input into the sample pool 1-4 to perform a two-dimensional single excitation scan on the sample to obtain a two-dimensional spectral signal of the sample.

[0024] In this embodiment, the specific optical path is as follows: Figure 3 As shown, the pulse light emitted by the locked optical comb 3-1 and the optical comb 3-2 is along Figure 2 The arrow direction is incident into 2D-AOD 3-3, and by changing the radio frequency signal loaded on 2D-AOD, 2D-AOD deflects a single pulse laser into a frequency-encoded two-dimensional laser beam array signal. Afterwards, the reflector 3-4 hits the two-dimensional laser beam array signal onto the first spatial beam splitter 3-5, dividing the array signal into two paths. One of the two signals converges on the first collimator 3-7-1 through the lens 3-6 and passes through the sample pool 3-8 to obtain the two-dimensional spectral information of the sample. Using the second collimator 3-7-2, lens 3-9 and reflector 3-10, the signal light carrying the sample information is hit on the second spatial beam splitter 3-11, and overlaps with the other pulse light as the reference signal. By adjusting the delay distance of the reference signal, the sample signal light overlaps with the reference signal and interferes. After the interference signal is converged by the lens 3-12, it is received by the high-speed photodetector 3-13, and finally the two-dimensional spectral information of the sample is restored through the two-dimensional spectral signal modulation and decoding module.

[0025] The above embodiment is one of the implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments and test examples. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Mid-infrared high repetition rate dual-comb ultrafast two-dimensional single-shot coherent measurement system, characterized by: It includes a first high repetition frequency mid-infrared light comb (1-1), a second high repetition frequency mid-infrared light comb (1-2), an acousto-optic deflector (1-3), a sample pool (1-4), a high-speed detector (1-5), a two-dimensional single excitation scanning signal decoding module (1-6) and a spectrum restoration module (1-7); The output mode-locked pulse signals of the first high repetition rate mid-infrared light comb (1-1) and the second high repetition rate mid-infrared light comb (1-2) are simultaneously input into an acousto-optic deflector (1-3) to generate a frequency-coded two-dimensional laser beam array with low third-order intermodulation distortion; the optical signal output by the acousto-optic deflector (1-3) is divided into two paths, one path is input into a sample pool (1-4) to obtain a two-dimensional spectrum signal of the sample, and the other path is used as a reference signal, which is spatially overlapped with the two-dimensional spectrum signal of the sample after passing through a delayed optical path for interference, and then a coherent signal is collected by a high-speed detector (1-5), and a two-dimensional single excitation scanning signal is used for decoding. The module (1-6) modulates and decodes the coherent signal of the two-dimensional single excitation, and finally restores the decoded signal into a two-dimensional spectral image through the spectrum restoration module (1-7); the repetition rates of the first high repetition frequency mid-infrared light comb (1-1) and the second high repetition frequency mid-infrared light comb (1-2) are locked on two stable frequency reference sources; wherein the repetition rate of the first high repetition frequency mid-infrared light comb (1-1) is f, and the repetition rate of the second high repetition frequency mid-infrared light comb (1-2) is f+△f, then the frequency difference △f between the two light combs is much smaller than the repetition frequency of the ultrashort pulse, △f<1MHz, f>1GHz; The acousto-optic deflector (1-3) is a two-dimensional single-shot scanning acousto-optic deflector (2D-AOD); The pulses emitted by the locked first high repetition frequency mid-infrared light comb and the second high repetition frequency mid-infrared light comb are incident on the acousto-optic deflector, and by changing the radio frequency signal loaded on the acousto-optic deflector, the acousto-optic deflector deflects a single beam of pulsed laser into a frequency-encoded two-dimensional laser beam array signal; a reflector is used to project the two-dimensional laser beam array signal onto the first spatial beam splitter, and the array signal is divided into two paths; one of the two paths of signals is converged on the first collimator through a lens and passes through the sample pool to obtain the two-dimensional spectral information of the sample; a second collimator, a lens and a reflector are used to allow the signal light carrying the sample information to hit the second spatial beam splitter and overlap with the other pulse light serving as a reference signal; by adjusting the delay distance of the reference signal, the sample signal light overlaps with the reference signal and interferes with it; the interference signal is received by a high-speed photodetector after being converged by the lens, and finally the two-dimensional spectral information of the sample is restored through a two-dimensional spectral signal modulation and decoding module.

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