A wavelength and phase adaptive phonon velocity detection device based on ISBS

Abstract

The application discloses a wavelength and phase self-adaptive phonon velocity detection device based on ISBS, and has the characteristics that the device comprises a light source, a self-adaptive feedback light path system, a sample container, a heterodyne signal light collecting device and a photoelectric detector; the self-adaptive feedback light path system comprises a wavelength self-adaptive tuning system, a focusing lens one, a transmission grating and a 4f lens device; the photoelectric detector is in communication connection with the self-adaptive feedback light path system, converts the light signal of the heterodyne signal light into a corresponding electric signal, feeds back to the self-adaptive feedback light path system to realize self-adaptive adjustment of the wavelength of pump light, the wavelength of detection light and the phase of detection light, and through subsequent data processing, the electric signal can obtain the phonon velocity of the sample. The electric signal collected by the photoelectric detector is fed back to the self-adaptive feedback light path system to realize self-adaptive adjustment of the wavelength and the phase, and the efficiency and the accuracy of the phonon velocity detection are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nonlinear optics, in particular to a wavelength and phase adaptive phonon velocity detection device based on ISBS. BACKGROUND

[0002] Phonon velocity is a basic physical quantity describing the vibration and mechanical response of the medium. By measuring the phonon velocity of the medium, the density, bulk modulus, gas or liquid medium composition and other parameters of the system can be analyzed and calculated. Therefore, the phonon velocity detection of the medium is of great significance.

[0003] Brillouin scattering technology is an optical detection method for measuring phonon velocity. Due to its unique advantages of non-contact, non-invasive and no label, it has become a powerful tool for phonon velocity detection. Based on the unique advantages and wide application of Brillouin scattering method for measuring phonon velocity, it is of great practical significance to further improve the detection efficiency. The technology based on impulsive stimulated Brillouin scattering (ISBS) can excite a stimulated Brillouin transient grating on the sample by two coherent pump lights, and then use a probe light to detect the excitation region to obtain the phonon velocity information of the sample. Compared with the traditional Brillouin scattering method, it can improve the signal strength, signal-to-noise ratio and signal acquisition speed, shorten the acquisition time, and has the advantages of simple structure and low cost. It has gradually become a hot research field of researchers. However, it can only measure the phonon velocity of the sample medium with a specific incident wavelength, which limits the selection of the sample and brings inconvenience to the measurement. Moreover, although the ISBS technology can greatly improve the intensity and signal-to-noise ratio of the stimulated Brillouin signal, the accuracy of the measurement result still needs to be further improved. SUMMARY

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a wavelength and phase adaptive phonon velocity detection device based on ISBS.

[0005] The technical solution for solving the technical problem of the present application is to provide a wavelength and phase adaptive phonon velocity detection device based on ISBS, characterized in that the device comprises a light source, an adaptive feedback optical system, a sample container, a heterodyne signal light collection device and a photodetector.

[0006] The adaptive feedback optical path system includes a wavelength adaptive tuning system, a focusing lens, a transmission grating, and a 4f lens device. The wavelength adaptive tuning system generates pump light and probe light, and adaptively adjusts the wavelengths of the pump light and probe light according to the detection signal of the photodetector. The focusing lens focuses the combined light formed by combining the pump light and probe light onto the transmission grating. The transmission grating causes the pump light and probe light to diffract. The 4f lens device retains only the positive and negative first-order diffraction beams of the pump light and the positive and negative first-order diffraction beams of the probe light. The beams of other diffraction orders are blocked in the Fourier space formed by the 4f lens device, and the phase of the positive first-order diffraction beam of the probe light is adaptively adjusted according to the detection signal of the photodetector.

[0007] Sample containers are used to hold the samples to be tested;

[0008] The heterodyne signal light acquisition device is used to remove the beam of light after it passes through the sample, and retain only the heterodyne signal light containing the phonon velocity information of the sample.

[0009] The photodetector is connected to the adaptive feedback optical path system to convert the optical signal of the heterodyne signal into a corresponding electrical signal, which is fed back to the adaptive feedback optical path system to achieve adaptive adjustment of the pump light wavelength, probe light wavelength and probe light phase. Furthermore, through subsequent data processing, the phonon velocity of the sample can be obtained from this electrical signal.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) This invention improves the efficiency and accuracy of phonon velocity detection by feeding back the electrical signal collected by the photodetector to the adaptive feedback optical path system to achieve adaptive adjustment of wavelength and phase.

[0012] (2) This invention expands the types of samples to be detected by wavelength adaptive adjustment, enabling the detection of phonon velocities of multiple samples or different components of the same sample. At the same time, it makes the detection signal performance better and the obtained phonon information more accurate.

[0013] (3) This invention eliminates the optical path difference between the pump light and the probe light through phase adaptive adjustment, which can more accurately detect the structure of the stimulated Brillouin transient grating. It can also achieve continuous phase adjustment of positive and negative phases, improve the intensity of heterodyne signal light, and improve detection efficiency.

[0014] (4) Through structural design, this invention improves the intensity, signal-to-noise ratio and acquisition speed of stimulated Brillouin signals, enabling more accurate detection of the structure of stimulated Brillouin transient gratings and improving the detection efficiency and accuracy of sample phonon velocities.

[0015] (5) The present application adopts 4f lens device, the excitation region of pump light is greatly improved in theory, the probe light automatically satisfies the Bragg condition of stimulated Brillouin transient grating in the sample, and a complex time delay alignment device is not needed.

[0016] (6) The present application has the characteristics of simple structure and convenient operation, and can be extended to the research of biomechanics in the future. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present application;

[0018] Figure 2 It is a schematic diagram of the structure of the adaptive feedback optical system of the present application.

[0019] In the figure, light source 1, adaptive feedback optical system 2, sample container 3, heterodyne signal light collection device 4, photodetector 5;

[0020] Wavelength adaptive tuning system 2-1, focusing lens one 2-2, transmission grating 2-3, 4f lens device 2-4;

[0021] Beam splitter 2-1-1, tunable filter one 2-1-2, diaphragm one 2-1-3, mirror one 2-1-4, mirror two 2-1-5, tunable filter two 2-1-6, diaphragm two 2-1-7, dichroic mirror 2-1-8;

[0022] Achromatic convex lens one 2-4-1, baffle one 2-4-2, neutral density filter 2-4-3, achromatic convex lens two 2-4-4, phase modulator 2-4-5;

[0023] Baffle two 4-1, mirror three 4-2, filter 4-3, diaphragm three 4-4, focusing lens two 4-5. DETAILED DESCRIPTION

[0024] The specific embodiments of the present application are given below. The specific embodiments are only used to further illustrate the present application, and do not limit the protection scope of the claims of the present application.

[0025] The present application provides a wavelength and phase adaptive phonon velocity detection device based on ISBS (referred to as device), characterized in that the device comprises a light source 1, an adaptive feedback optical system 2, a sample container 3, a heterodyne signal light collection device 4 and a photodetector 5;

[0026] The light source 1 is a high-power picosecond pulse supercontinuum spectrum light source, which provides pump light and probe light;

[0027] The adaptive feedback optical system 2 comprises a wavelength adaptive tuning system 2-1, a focusing lens one 2-2, a transmission grating 2-3 and a 4f lens device 2-4; the wavelength adaptive tuning system 2-1 forms pump light and probe light, and adaptively adjusts the wavelengths of the pump light and the probe light according to a detection signal of a photodetector 5; the focusing lens one 2-2 converges the combined light formed by the pump light and the probe light on the transmission grating 2-3; the transmission grating 2-3 diffracts the pump light and the probe light; the 4f lens device 2-4 only retains the two coherent pump light and probe light (i.e. the positive and negative first-order diffracted light of the pump light and the positive and negative first-order diffracted light of the probe light), and blocks the light beams of the remaining diffraction orders in the Fourier space formed by the 4f lens device 2-4, and adaptively adjusts the phase of the positive first-order diffracted light of the probe light according to the detection signal of the photodetector 5;

[0028] The sample container 3 is used for placing a sample to be measured;

[0029] The heterodyne signal light collection device 4 is used for removing the light beams passing through the sample, and only retaining the heterodyne signal light containing the phonon velocity information of the sample;

[0030] The photodetector 5 is in communication connection with the adaptive feedback optical system 2, converts the optical signal of the heterodyne signal light into a corresponding electrical signal, feeds back to the adaptive feedback optical system 2 to realize adaptive adjustment of the wavelengths of the pump light and the probe light and the phase of the probe light, and through subsequent data processing, the electrical signal can obtain the phonon velocity of the sample.

[0031] Preferably, the wavelength adaptive tuning system 2-1 comprises a beam splitter 2-1-1, a tunable filter one 2-1-2, a mirror one 2-1-4, a mirror two 2-1-5, a tunable filter two 2-1-6 and a dichroic mirror 2-1-8; the 4f lens device 2-4 comprises an achromatic convex lens one 2-4-1 (the focal length f1 = 75 mm in this embodiment), a baffle one 2-4-2, an achromatic convex lens two 2-4-4 (the focal length f2 = 300 mm in this embodiment) and a phase modulator 2-4-5;

[0032] The beam splitter 2-1-1 is used for splitting the light (in this embodiment, supercontinuum light) emitted by the light source 1 into transmitted light and reflected light; the tunable filter one 2-1-2 is used for adjusting the transmitted light into light of a fixed wavelength as pump light; the mirror one 2-1-4 is used for guiding the pump light into the dichroic mirror 2-1-8; the tunable filter two 2-1-6 is used for adjusting the reflected light into light of a fixed wavelength as probe light; the mirror two 2-1-5 is used for guiding the probe light into the dichroic mirror 2-1-8; the dichroic mirror 2-1-8 is used for combining the pump light and the probe light to form combined light;

[0033] The Fourier space is formed between the achromatic convex lens one 2-4-1 and the achromatic convex lens two 2-4-4; the baffle one 2-4-2 is used to remove the zero-order diffraction light of the pump light and the probe light; except the positive and negative first-order diffraction light of the pump light and the probe light, the rest diffraction orders are blocked in the Fourier space; the phase modulator 2-4-5 is arranged on the light path of the positive first-order diffraction light of the probe light.

[0034] Preferably, the light path of the light emitted by the light source 1 is coincident with the light path of the incident light of the beam splitter 2-1-1; the light path of the transmitted light of the beam splitter 2-1-1 is coincident with the light path of the incident light of the tunable filter one 2-1-2; the light path of the emitted light of the tunable filter one 2-1-2 is coincident with the light path of the incident light of the mirror one 2-1-4; the light path of the reflected light of the mirror one 2-1-4 is coincident with the light path of the incident light of the dichroic mirror 2-1-8; the light path of the reflected light of the beam splitter 2-1-1 is coincident with the light path of the incident light of the mirror two 2-1-5; the light path of the reflected light of the mirror two 2-1-5 is coincident with the light path of the incident light of the tunable filter two 2-1-6; the light path of the emitted light of the tunable filter two 2-1-6 is coincident with the light path of the incident light of the dichroic mirror 2-1-8; the light path of the emitted light of the dichroic mirror 2-1-8 is coincident with the light path of the incident light of the focusing lens one 2-2;

[0035] The light path of the emitted light of the focusing lens one 2-2 is coincident with the light path of the incident light of the transmission grating 2-3; the light path of the diffracted light of the transmission grating 2-3 is coincident with the light path of the incident light of the achromatic convex lens one 2-4-1; the light path of the emitted light of the achromatic convex lens one 2-4-1 is coincident with the light path of the incident light of the achromatic convex lens two 2-4-4; the light path of the emitted light of the achromatic convex lens two 2-4-4 is coincident with the light path of the incident light of the sample in the sample container 3; the Fourier space is formed between the achromatic convex lens one 2-4-1 and the achromatic convex lens two 2-4-4; the baffle one 2-4-2 is arranged on the central extension line of the focusing lens one 2-2 and is located in the Fourier space for removing the zero-order diffraction light of the pump light and the probe light; except the positive and negative first-order diffraction light of the pump light and the probe light, the rest diffraction orders are blocked in the Fourier space; the phase modulator 2-4-5 is arranged on the light path of the positive first-order diffraction light of the probe light;

[0036] The light path of the emitted light of the sample in the sample container 3 is coincident with the light path of the incident light of the heterodyne signal light collecting device 4; the emitted light of the heterodyne signal light collecting device 4 is incident into the photodetector 5, and the optical signal of the heterodyne signal light (i.e. the mixed frequency light composed of the Bragg diffraction light of the probe light and the local oscillator light of the probe light) is converted into an electrical signal in the photodetector 5;

[0037] The photodetector 5 is communicatively connected with the tunable filter one 2-1-2, the tunable filter two 2-1-6 and the phase modulator 2-4-5 respectively for signal transmission.

[0038] Preferably, the wavelength adaptive tuning system 2-1 further comprises diaphragm one 2-1-3 and diaphragm two 2-1-7; the light path of the tunable filter one 2-1-2 coincides with the light path of the mirror one 2-1-4, and the diaphragm one 2-1-3 is arranged between the light paths; the light path of the tunable filter two 2-1-6 coincides with the light path of the dichroic mirror 2-1-8, and the diaphragm two 2-1-7 is arranged between the light paths. The diaphragm one 2-1-3 and the diaphragm two 2-1-7 are used to reduce the beam aperture and adjust the spot shape to make it more standardized.

[0039] Preferably, the transmission grating 2-3 is a blazed grating, and the blazed wavelength corresponds to the wavelength of the pump light and the probe light.

[0040] Preferably, the 4f lens device 2-4 further comprises a neutral density filter 2-4-3; the neutral density filter 2-4-3 is arranged on the light path of the negative first-order diffraction light of the probe light, used to reduce the light intensity of the local oscillator light of the probe light, facilitate matching with the Bragg diffraction light of the probe light, and then obtain the heterodyne signal light.

[0041] Preferably, the heterodyne signal light collecting device 4 comprises a baffle two 4-1, a mirror three 4-2, a filter 4-3 and a focusing lens two 4-5; the baffle two 4-1 is used to remove part of the pump light; the mirror three 4-2 is used to reflect the heterodyne signal light and part of the pump light onto the filter 4-3; the filter 4-3 is used to filter out all the pump light; and the focusing lens two 4-5 is used to focus the heterodyne signal light into the photodetector 5.

[0042] Preferably, the transmission light paths of the negative first-order diffraction light of the pump light and the negative first-order diffraction light of the probe light of the sample in the sample container 3 coincide with the light path of the mirror three 4-2; the transmission light paths of the positive first-order diffraction light of the pump light and the positive first-order diffraction light of the probe light of the sample in the sample container 3 are provided with the baffle two 4-1 for removing part of the pump light; the reflection light path of the mirror three 4-2 coincides with the light path of the filter 4-3, and all the pump light is filtered out through the filter 4-3; the light path of the filter 4-3 coincides with the light path of the focusing lens two 4-5; and the light emitted from the focusing lens two 4-5 is incident into the photodetector 5.

[0043] Preferably, the heterodyne signal light collecting device 4 further comprises a diaphragm three 4-4; the light path of the filter 4-3 coincides with the light path of the focusing lens two 4-5, and the diaphragm three 4-4 is arranged between the light paths; the diaphragm three 4-4 is used to reduce the beam aperture and adjust the spot shape to make it more standardized.

[0044] Preferably, in order to better filter out the pump light and improve the signal-to-noise ratio of the heterodyne signal light, the mirror three 4-2 is coated with a high reflection film, and the filter 4-3 adopts a long-pass filter.

[0045] The working principle and working process of the present application are as follows:

[0046] In use, the picosecond pulse supercontinuum light emitted by the light source 1 enters the wavelength adaptive tuning system 2-1, the supercontinuum light is divided into transmitted light and reflected light by the beam splitter 2-1-1, and the transmitted light and the reflected light are perpendicular to each other;

[0047] The transmitted light enters the tunable filter one 2-1-2, adjusts the transmitted light into fixed wavelength light as pump light, and is guided into the dichroic mirror 2-1-8 by the mirror one 2-1-4; the reflected light is guided into the tunable filter two 2-1-6 by the mirror two 2-1-5, adjusts the reflected light into fixed wavelength light as probe light, and then enters the dichroic mirror 2-1-8; in the dichroic mirror 2-1-8, the wave band of the pump light is reflected and the wave band of the probe light is transmitted, the pump light and the probe light are combined to form combined light; the combined light converges through the focusing lens one 2-2 to obtain a focused light beam; the focused light beam converges on the transmission grating 2-3 to diffract, and the 4f lens device 2-4 selects the positive and negative first-order diffracted light of the pump light and the positive and negative first-order diffracted light of the probe light to converge on the sample in the sample container 3; wherein the positive and negative first-order diffracted light of the pump light is used as excitation light to excite the ISBS effect in the sample in the sample container 3, and a stimulated Brillouin transient grating is generated; the positive and negative first-order diffracted light of the probe light is Bragg diffracted through the stimulated Brillouin transient grating to obtain Bragg diffracted light of the probe light, and the Bragg diffracted light of the probe light contains the phonon velocity information of the sample;

[0048] After passing through the sample, the light beam (including the Bragg diffracted light of the probe light, the local oscillator light of the probe light and the pump light, and the heterodyne signal light composed of the Bragg diffracted light of the probe light and the local oscillator light), after removing part of the pump light through the baffle two 4-1, the heterodyne signal light and part of the pump light are reflected to the filter 4-3 through the mirror three 4-2, all the pump light is filtered out by the filter 4-3, and then the light beam is reduced by the diaphragm three 4-4 to obtain the heterodyne signal light; then the heterodyne signal light is focused on the photodetector 5 through the focusing lens two 4-5, the Bragg diffracted light of the probe light is used as incident signal light, and the local oscillator light of the probe light is used as reference light, the light signal is converted into corresponding electrical signal in the photodetector 5 through the heterodyne detection method, and then the electrical signal is converted into time domain waveform through data processing by the external computer and the like; then the time domain waveform is subjected to Fourier transform to obtain the Fourier frequency, which is the phonon frequency f (also known as the Brillouin frequency); through the formulas d = (g x f2) / (2 x f1) and f = (4 x c s x f1) / (g x f2), wherein d is the grating fringe spacing, g is the transmission grating constant, f1 is the focal length of the achromatic convex lens one 2-4-1, f2 is the focal length of the achromatic convex lens two 2-4-4, and the phonon velocity c s of the sample is obtained as f x d / 2.

[0049] After the kind of sample in the sample container 3 is installed or replaced, the corresponding electrical signal generated by the photodetector 5 is fed back to the adaptive feedback optical system 2, and the tunable filter one 2-1-2 and the tunable filter two 2-1-6 are adaptively adjusted according to the electrical signal to achieve the wavelength adaptive adjustment; the phase modulator 2-4-5 adaptively adjusts the phase of the first-order positive diffraction light of the probe light according to the electrical signal, eliminates the optical path difference between the pump light and the probe light, and can realize continuous phase adjustment of positive and negative phases, improve the intensity of the heterodyne signal light, and improve the detection efficiency.

[0050] Preferably, the tunable filter one 2-1-2 and the tunable filter two 2-1-6 can be set with a default initial value in advance, and the photodetector 5 obtains the corresponding electrical signal (i.e. the initial electrical signal), and then feeds back the electrical signal to the tunable filter one 2-1-2, the tunable filter two 2-1-6 and the phase modulator 2-4-5 for feedback adjustment.

[0051] The unmentioned part of the present application is applicable to the prior art.

Claims

1. A wavelength and phase adaptive phonon velocity detection device based on ISBS, characterized in that, The device includes a light source, an adaptive feedback optical path system, a sample container, a heterodyne signal light acquisition device, and a photodetector; The adaptive feedback optical path system includes a wavelength adaptive tuning system, a focusing lens, a transmission grating, and a 4f lens assembly; The wavelength adaptive tuning system generates pump and probe beams and adaptively adjusts their wavelengths according to the detection signal from the photodetector. The focusing lens converges the combined beam of the pump and probe beams onto the transmission grating. The transmission grating causes diffraction of the pump and probe beams. The 4f lens device retains only the positive and negative first-order diffraction beams of the pump and probe beams, while the beams of other diffraction orders are blocked in the Fourier space formed by the 4f lens device. The phase of the positive first-order diffraction beam of the probe beam is adaptively adjusted according to the detection signal from the photodetector. Sample containers are used to hold the samples to be tested; The heterodyne signal light acquisition device is used to remove the beam of light after it passes through the sample, and retain only the heterodyne signal light containing the sample phonon velocity information; The photodetector is connected to the adaptive feedback optical path system to convert the optical signal of the heterodyne signal into a corresponding electrical signal, which is fed back to the adaptive feedback optical path system to achieve adaptive adjustment of the pump light wavelength, probe light wavelength and probe light phase. Furthermore, the electrical signal can be processed by subsequent data processing to obtain the phonon velocity of the sample. The wavelength adaptive tuning system includes a beam splitter, a tunable filter one, a reflector one, a reflector two, a tunable filter two, and a dichroic mirror; the 4f lens device includes an achromatic convex lens one, a baffle one, an achromatic convex lens two, and a phase modulator. A beam splitter is used to split the light emitted from the light source into transmitted light and reflected light; a tunable filter is used to adjust the transmitted light to a fixed wavelength as pump light; a reflector is used to guide the pump light into a dichroic mirror; a tunable filter is used to adjust the reflected light to a fixed wavelength as probe light; a reflector is used to guide the probe light into a dichroic mirror; and the dichroic mirror is used to combine the pump light and the probe light to form a combined beam. A Fourier space is formed between achromatic convex lens one and achromatic convex lens two; baffle one is used to remove the zeroth order diffraction light of pump light and probe light; except for the positive and negative first order diffraction light of pump light and probe light, the other diffraction orders are blocked in the Fourier space; the phase modulator is set in the optical path of the positive first order diffraction light of probe light. The light path of the emitted light from the light source coincides with the light path of the incident light from the beam splitter; the light path of the transmitted light from the beam splitter coincides with the light path of the incident light from the first tunable filter; the light path of the emitted light from the first tunable filter coincides with the light path of the incident light from the first reflector; and the light path of the reflected light from the first reflector coincides with the light path of the incident light from the dichroic mirror. The reflected light path of the beam splitter coincides with the incident light path of the second reflector; the reflected light path of the second reflector coincides with the incident light path of the second tunable filter; the outgoing light path of the second tunable filter coincides with the incident light path of the dichroic mirror; and the outgoing light path of the dichroic mirror coincides with the incident light path of the first focusing lens. The outgoing light path of focusing lens one coincides with the incoming light path of the transmission grating; the diffracted light path of the transmission grating coincides with the incoming light path of achromatic convex lens one; the outgoing light path of achromatic convex lens one coincides with the incoming light path of achromatic convex lens two; the outgoing light path of achromatic convex lens two coincides with the incoming light path of the sample in the sample container; baffle one is located on the central extension line of focusing lens one and is situated in Fourier space. The outgoing light path of the sample in the sample container coincides with the incoming light path of the heterodyne signal light acquisition device; The emitted light from the heterodyne signal light acquisition device enters the photodetector, where the optical signal of the heterodyne signal light is converted into an electrical signal. The photodetector is communicatively connected to tunable filter one, tunable filter two, and phase modulator, respectively.

2. The wavelength and phase adaptive phonon velocity detection device based on ISBS according to claim 1, characterized in that, The wavelength adaptive tuning system also includes an aperture 1 and an aperture 2; aperture 1 and aperture 2 are used to reduce the beam aperture; aperture 1 is provided between the optical paths of tunable filter 1 and mirror 1; aperture 2 is provided between the optical paths of tunable filter 2 and dichroic mirror.

3. The wavelength and phase adaptive phonon velocity detection device based on ISBS according to any one of claims 1, characterized in that, The transmission grating is a blazed grating, and the blazed wavelength corresponds to the wavelengths of the pump light and the probe light.

4. The wavelength and phase adaptive phonon velocity detection device based on ISBS according to claim 1, characterized in that, The 4f lens device also includes a neutral density filter; the neutral density filter is placed in the optical path of the negative first-order diffraction of the probe light, so that the intensity of the local oscillator light of the probe light matches the Bragg diffraction light of the probe light, thereby obtaining the heterodyne signal light.

5. The ISBS-based wavelength and phase adaptive phonon velocity detection device according to claim 1, characterized in that, The heterodyne signal light acquisition device includes a second baffle, a third reflector, a filter, and a second focusing lens; Baffle 2 is used to remove part of the pump light; mirror 3 is used to reflect the heterodyne signal light and part of the pump light onto the filter; the filter is used to filter out all the pump light; focusing lens 2 is used to focus the heterodyne signal light into the photodetector.

6. The ISBS-based wavelength and phase adaptive phonon velocity detection device according to claim 5, characterized in that, The transmitted light paths of the negative first-order diffracted light of the pump light and the negative first-order diffracted light of the probe light of the sample in the sample container coincide with the incident light path of the third reflector; a baffle two is provided on the transmitted light path of the positive first-order diffracted light of the pump light and the positive first-order diffracted light of the probe light of the sample in the sample container; the reflected light path of the third reflector coincides with the incident light path of the filter; the emitted light path of the filter coincides with the incident light path of the second focusing lens; the emitted light of the second focusing lens enters the photodetector.

7. The ISBS-based wavelength and phase adaptive phonon velocity detection device according to claim 5, characterized in that, The heterodyne signal light acquisition device also includes an aperture three; the aperture three is used to reduce the beam aperture and is set between the filter and the focusing lens two in the optical path.

8. The ISBS-based wavelength and phase adaptive phonon velocity detection device according to claim 5, characterized in that, The reflector is triple-coated with a high-reflectivity film, and the filter is a long-pass filter.

Images