SBS phase conjugation mirror capable of displaying acoustic wave field in real time

Abstract

The application discloses an SBS phase conjugation mirror capable of displaying a sound wave field in real time, and belongs to the technical field of nonlinear optics.The application comprises the following steps: pump light passes through a half-wave plate and a polarization beam splitter, passes through an optical isolator, changes a polarization state through a quarter-wave plate, is focused through a focusing lens, and then enters an SBS medium pool, stimulated Brillouin scattering occurs, a periodic density modulation is formed in the medium, and an equivalent acousto-optic grating structure is generated.Through introducing an independent probe light beam, the probe light enters the SBS medium pool at an incident angle satisfying the Bragg diffraction condition, and the probe light will be diffracted on the acousto-optic grating formed by the sound wave field.The intensity of the diffracted light changes with the intensity of the sound wave field, so that the real-time measurement of the sound wave field waveform and the life parameter in the SBS process can be realized by detecting the change of the diffracted light intensity with time.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear optical technology, and specifically relates to an SBS phase conjugate mirror that can display acoustic wave fields in real time. Background Technology

[0002] Stimulated Brillouin scattering (SBS) has attracted widespread attention due to its high energy conversion efficiency, small Brillouin frequency shift, and phase conjugation. Currently, SBS has been applied in Brillouin spectroscopy, pulse width compression, and beam shaping. However, the generation and evolution of its core process—the acoustic wave field—has long remained a black box. Typically, what happens internally can only be indirectly inferred by measuring the scattered light. This lack of direct measurement capability for the acoustic wave field has hindered our understanding of the fundamental mechanisms of SBS, optimization of its performance, breakthroughs in existing technological bottlenecks, and exploration of new applications.

[0003] Therefore, it is necessary to provide a device that can directly and accurately measure the acoustic field, which is the key to breaking through the current bottleneck in the research and application of stimulated Brillouin scattering and unleashing its potential. Summary of the Invention

[0004] The purpose of this invention is to provide an SBS phase conjugate mirror that can display acoustic wave fields in real time. By controlling the intensity and phase of the pump light, different acoustic wave fields are excited, and then a special probe light path is used to incident on the acoustic wave field at a Bragg angle to realize the measurement of the waveform and lifetime of the acoustic wave field.

[0005] To achieve the above objectives, the present invention provides an SBS phase conjugate mirror capable of displaying acoustic wave fields in real time, comprising: a pump source, a first half-wave plate, a first polarization beam splitter, a second polarization beam splitter, a Faraday rotator, a second half-wave plate, a third polarization beam splitter, a fourth polarization beam splitter, a quarter-wave plate, a focusing lens, an SBS dielectric cell, and an acoustic wave field measurement device. The pump light passes sequentially through the first half-wave plate and the first polarization beam splitter, which modulate the intensity and phase of the pump light. Then it passes through an optical isolator composed of a second polarization beam splitter, a Faraday rotator, a second half-wave plate, and a third polarization beam splitter. At this point, the laser light, which is parallel linearly polarized, is transmitted through the fourth polarization beam splitter. After passing through a quarter-wave plate, it changes from parallel linearly polarized light to circularly polarized light. After being focused by a focusing lens, it enters the SBS dielectric cell, where stimulated Brillouin scattering occurs and an acoustic wave field is excited. The resulting Stokes pulse laser returns along the original path, passes through another quarter-wave plate, and changes from circularly polarized light to vertically polarized light. Finally, the output light is reflected and output through the fourth polarization beam splitter.

[0006] Preferably, the acoustic field measurement device includes: a detection light source, a first total reflection mirror, a second total reflection mirror, a third total reflection mirror, and a photoelectric probe; The probe light emitted by the probe light source is collimated by the first and second total reflection mirrors to ensure that it is parallel to the pump light path. After passing through the third total reflection mirror, it is incident at a Bragg angle with the SBS dielectric cell. The probe light reaches the photodetector for measurement after being diffracted by the acoustic field.

[0007] Preferably, the optical isolator includes a second polarization beam splitter, a Faraday rotator, a second half-wave plate, and a third polarization beam splitter; wherein the Faraday rotator is used to rotate the polarization plane of the beam by 45° using the magneto-optical effect, the second half-wave plate is used to adjust the polarization state, and the transmission angle between the second polarization beam splitter and the third polarization beam splitter should be 45°.

[0008] Preferably, the probe light should be incident at a specific angle to the SBS dielectric cell, and the incident angle θ is obtained by Bragg's formula 2Λsinθ=nλ. Where n is the diffraction order, typically 1; λ is the probe wavelength; Λ is the grating pitch. Since the reflected Stokes light is being calculated, the scattering angle θ1 is taken as 180°. Given the pump light wavelength λ1 and the refractive index of the medium n1, according to... The grid pitch Λ is obtained.

[0009] Preferably, the photoelectric probe is used to record the signal of the change in light intensity over time after the probe light is diffracted by the acoustic field, thereby obtaining the waveform information and lifetime parameters of the acoustic field.

[0010] Preferably, the medium in the SBS medium pool is a liquid fluorocarbon compound.

[0011] Preferably, the probe light should be a continuous laser with a wavelength of 632 nm to 1064 nm.

[0012] Preferably, the focusing lens has a focal length of 50mm to 250mm.

[0013] The beneficial effects of this invention are: In this invention, the pump light passes through a half-wave plate and a polarization beam splitter, then through an optical isolator. Its polarization state is altered by a quarter-wave plate, and after being focused by a focusing lens, it enters the SBS dielectric cell, where stimulated Brillouin scattering occurs. This creates periodic density modulation within the dielectric, resulting in an equivalent acousto-optic grating structure. By introducing an independent probe beam and ensuring its incident angle satisfies the Bragg diffraction condition, the probe beam diffracts on the acousto-optic grating formed by the acoustic field. The intensity of the diffracted light varies with the acoustic field intensity; therefore, by detecting the change in diffracted light intensity over time, real-time measurement of the acoustic field waveform and lifetime parameters during the SBS process can be achieved.

[0014] This invention provides an SBS phase conjugate mirror and method for real-time display of acoustic fields. By optimizing structural parameters, higher Brillouin conversion efficiency can be achieved. A unique measurement device is used to measure the acoustic field parameters generated during Brillouin scattering. The optical path of this invention is simple and convenient to implement, enabling a low-cost, miniaturized acoustic field testing system. The probe light in this invention is continuous, and through the cooperation of three total reflection mirrors, the probe light is incident at a Bragg angle with the SBS dielectric cell. The faster the pump light frequency, the denser the displayed acoustic field, enabling real-time display of the acoustic field. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. In the drawings, several embodiments of the present invention are shown by way of example and not limitation, wherein: Figure 1 This is a schematic diagram of the structure of an SBS phase conjugate mirror that can display the acoustic wave field in real time, as proposed in this invention. Figure 2 Output the Stokes light waveform for Example 1; Figure 3 The pump light spot is shown in Example 1; Figure 4 The Stokes spot of Example 1; Figure 5 The waveform is the original acoustic field simulation waveform of Example 2.

[0016] Figure labeling: 1: Pump source; 2: First half-wave plate; 3: First polarization beam splitter; 4: Second polarization beam splitter; 5: Faraday rotator; 6: Second half-wave plate; 7: Third polarization beam splitter; 8: Fourth polarization beam splitter; 9: Quarter-wave plate; 10: Focusing lens; 11: SBS dielectric cell; 12: Probe light source; 13: First total reflection mirror; 14: Second total reflection mirror; 15: Third total reflection mirror; 16: Photodetector. Detailed Implementation

[0017] To clearly illustrate the objectives, technical solutions, and advantages of this invention, the embodiments of the invention will be described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described herein are only a part of the implementation of this invention, and not all of them. The structure and configuration of the components shown in the accompanying drawings may also vary. Therefore, this detailed description should not be construed as limiting the scope of the invention, but is intended to fully illustrate the technical content of the invention through representative embodiments. All other embodiments obtained by those skilled in the art based on the embodiments disclosed in this document without creative effort are within the scope of protection claimed by this invention.

[0018] like Figure 1 As shown, the present invention provides an SBS phase conjugate mirror capable of real-time display of acoustic wave fields, comprising: A stimulated Brillouin acoustic field generation system is used to generate a sound field by inducing stimulated Brillouin scattering.

[0019] The acoustic field measurement device is used to detect the acoustic field waveform and lifetime parameters generated during the SBS process.

[0020] The stimulated Brillouin acoustic wave field generation system includes: pump source 1, first half-wave plate 2, first polarization beam splitter 3, second polarization beam splitter 4, Faraday rotator 5, second half-wave plate 6, third polarization beam splitter 7, fourth polarization beam splitter 8, quarter-wave plate 9, focusing lens 10, and SBS dielectric cell 11.

[0021] The beam emitted from pump source 1 undergoes polarization by the first half-wave plate 2, and then passes through the first polarization beam splitter 3 to fix the linearly polarized light, thus forming an energy control system to control the energy entering the subsequent optical path. After passing through the second polarization beam splitter 4 and Faraday rotator 5, the optical path then passes through the second half-wave plate 6 and the third polarization beam splitter 7 to form a Faraday isolator, which eliminates back-reflected light and protects the laser. The still parallel linearly polarized light then propagates through the fourth polarization beam splitter 8. After passing through the quarter-wave plate 9 for the first time, it becomes circularly polarized light, is focused by the focusing lens 10, and enters the SBS dielectric cell 11 to undergo the SBS reaction, simultaneously exciting the acoustic field. The resulting Stokes light returns along the same path, passes through the quarter-wave plate 9 again, becomes vertically polarized light, and is reflected by the fourth polarization beam splitter 8 before being output.

[0022] The acoustic field measurement device includes: a detection light source 12, a first total reflection mirror 13, a second total reflection mirror 14, a third total reflection mirror 15, and a photoelectric probe 16.

[0023] The acoustic field measurement device emits a probe light from the probe light source 12, which is then collimated by the first total reflection mirror 13 and the second total reflection mirror 14 to ensure that it is parallel to the pump light path. After passing through the third total reflection mirror 15, it is incident at an angle that satisfies the Bragg diffraction condition with the dielectric cell 11. After being diffracted by the acoustic field, the probe light reaches the photodetector 16 for measurement.

[0024] Example 1 Pump source 1 emits a laser with a wavelength of 1064nm and an output energy of 100mJ (pulse mode, pulse width 10ns, repetition frequency 1Hz). The phase and intensity are controlled by the first half-wave plate 2 and the first polarization beam splitter 3. Then, it passes through an optical isolation system composed of the second polarization beam splitter 4, the Faraday rotator 5, the second half-wave plate 6, and the third polarization beam splitter 7 to eliminate the back-returning light. At this time, the laser is parallel linearly polarized light and will continue to transmit through the fourth polarization beam splitter. After passing through the quarter-wave plate 9 for the first time, it becomes circularly polarized light. After being focused by a focusing lens with a focal length of f=100mm, it enters the 20cm long SBS dielectric cell 11 (medium is FC-770, refractive index 1.270) and undergoes stimulated Brillouin scattering. At the same time, it excites the acoustic wave field. The generated Stokes light will return along the same path. After passing through the quarter-wave plate 9 again, it becomes vertically linearly polarized light and is reflected and output by the fourth polarization beam splitter 8.

[0025] like Figure 2 As shown, Figure 2 To measure the Stokes light waveform.

[0026] like Figure 3 As shown, Figure 3 This is the pump light spot.

[0027] like Figure 4 As shown, Figure 4 This is a Stokes light spot.

[0028] Example 2 The probe light source 12 emits a visible red helium-neon laser with a wavelength of 632 nm. After being transmitted and collimated by the first total internal reflection mirror 13 and the second total internal reflection mirror 14 to ensure parallelism with the pump light path, it passes through the third total internal reflection mirror 15 and is incident at a specific angle with the dielectric cell 11. The FC-770 dielectric has a refractive index of 1.270, the pump light wavelength is 1064 nm, and the probe light wavelength is 632 nm. The specific incident angle is calculated to be 49° using Bragg's law. The probe light then reaches the photodetector 16 for measurement after being diffracted by the acoustic field.

[0029] like Figure 5 As shown, Figure 5 The waveform is the original acoustic field simulation waveform.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

[0031] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. An SBS phase conjugate mirror capable of real-time display of acoustic wave fields, characterized in that, include: Pump source, first half-wave plate, first polarization beam splitter, second polarization beam splitter, Faraday rotator, second half-wave plate, third polarization beam splitter, fourth polarization beam splitter, quarter-wave plate, focusing lens, SBS dielectric cell, acoustic field measurement device. The pump light sequentially passes through the first half-wave plate, the first polarization beam splitter, the second polarization beam splitter, the Faraday rotator, the second half-wave plate, the third polarization beam splitter, and the quarter-wave plate. After being focused by the focusing lens, it enters the SBS dielectric cell, where stimulated Brillouin scattering occurs, exciting the acoustic field and thus generating an equivalent acousto-optic grating structure. The generated Stokes pulse laser returns along the same path, passes through the quarter-wave plate again, and is finally reflected by the fourth polarization beam splitter. The generated acoustic field is then detected by an acoustic field measurement device.

2. The SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The acoustic field measurement device includes: a detection light source, a first total reflection mirror, a second total reflection mirror, a third total reflection mirror, and a photoelectric probe; The probe light emitted by the probe light source is collimated by the first and second total reflection mirrors to ensure that it is parallel to the pump light path. After passing through the third total reflection mirror, it is incident at a Bragg angle with the SBS dielectric cell. The probe light reaches the photodetector for measurement after being diffracted by the acoustic field.

3. The SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The optical isolator includes a second polarization beam splitter, a Faraday rotator, a second half-wave plate, and a third polarization beam splitter; wherein the Faraday rotator is used to rotate the polarization plane of the beam by 45° using the magneto-optical effect, the second half-wave plate is used to adjust the polarization state, and the transmission angle between the second polarization beam splitter and the third polarization beam splitter should be 45°.

4. The SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The probe light is incident on the SBS dielectric cell at a Bragg angle. The incident angle θ is obtained by 2Λsinθ=nλ, where n is the diffraction order, which is 1, λ is the wavelength of the probe light, and Λ is the grating pitch. Because we are calculating the reflected Stokes light, the scattering angle θ1 is taken as 180°. Given the pump light wavelength λ1 and the refractive index of the medium n1, according to... The grid pitch Λ is obtained.

5. An SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The photoelectric probe is used to record the signal of the light intensity changing over time after the probe light is diffracted by the acoustic field, thereby obtaining the waveform information and lifetime parameters of the acoustic field.

6. The SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The medium in the SBS medium pool is a liquid fluorocarbon.

7. An SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The probe light is selected from a continuous-wave laser ranging from 632nm to 1064nm.

8. An SBS phase conjugate mirror capable of real-time display of acoustic wave field according to claim 1, characterized in that, The focal length of the focusing lens is from 50mm to 250mm.

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