Arbitrary structure light stimulated Brillouin scattering phase conjugation device and method

Abstract

The present invention provides a device and method for phase conjugation of stimulated Brillouin scattering of arbitrary structured light, which belongs to the field of optoelectronic devices and can solve the problems of low fidelity and the like existing in the existing optical phase conjugation technology. The first pumping light beam is incident on the SBS medium pool through a focusing lens and focused, and the first pumping light beam is a structured light; at least one second pumping light beam is incident on the SBS medium pool, cross-interferes with the first pumping light beam, destroys the spatial distribution of the first pumping light beam, and beats with the backward structured light Stokes wave generated after the first pumping light beam is focused, so that at least one second pumping light beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pumping light beam is focused is the phase conjugate light of the first pumping light beam. The above technology of the present invention can be used for high-fidelity, low-threshold phase conjugation of an arbitrary structured light field containing an OAM light beam.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic devices, and in particular relates to a device and method for phase conjugation of stimulated Brillouin scattering of arbitrary structured light. Background Art

[0002] Optical phase conjugation refers to the use of optical nonlinear effects to accurately invert the propagation direction and phase factor of each plane wave component of an arbitrary light beam. The device that produces optical phase conjugation light is called a phase conjugation mirror (PCM). Common methods for producing phase conjugation include stimulated Brillouin scattering (SBS), four-wave mixing, stimulated Raman scattering, and two-photon absorption. SBS is a third-order nonlinear optical effect based on photoacoustic coupling. It has the advantages of simple structure, high fidelity and high conversion efficiency. Therefore, it has important applications in high-power narrow-linewidth lasers, microscopic imaging, Brillouin lidar, and distributed fiber optic sensing. At present, the SBS system mainly has structures such as focused single cell, compact double cell, and independent double cell. The focused single cell structure originates from noise and forms a dynamic grating at the frequency of the acoustic wave, which contains the phase distortion information of the incident wave and can achieve optical phase conjugation.

[0003] In recent years, spatially structured light fields with inhomogeneous lateral distributions of amplitude, phase, and polarization have attracted much attention due to their extraordinary properties in their propagation and light-matter interaction, especially light fields carrying orbital angular momentum (OAM) and other global spatial modes.

[0004] However, the spatial mode quality of the structured light field is easily affected by the wavefront distortion caused by atmospheric turbulence and other scattering media, resulting in the fact that the distortion correction of OAM beams with phase singularities is still difficult to achieve. Optical phase conjugation is one of the feasible methods to achieve distortion correction. Under the existing method, the traditional focused single-pump SBS-type PCM can be used to achieve phase conjugation of different spatial mode structured light fields. However, this method cannot achieve phase conjugation of structured light fields carrying OAM, because the SBS process caused by noise cannot select a single mode conjugated with the pump, and the incident light beam with OAM exhibits a petal-shaped degenerate OAM mode in the traditional focused single-cell SBS reflection process. Although the method of using a random phase plate to destroy the pump structure, which was proposed in the 2017 Chinese Optics Letters Vol. 3, No. 15, can alleviate this problem, the fidelity of the reflected SBS signal is still not ideal. In addition, the PCM of traditional focused single-pump SBS requires a sufficiently high pump power, which hinders its application in weak-light SBS.

[0005] Therefore, there is an urgent need for a simple, easy-to-operate device to achieve high-fidelity, low-threshold phase conjugation of arbitrarily structured light fields containing OAM beams. Summary of the invention

[0006] In view of the above problems, the present invention proposes a phase conjugation device and method for stimulated Brillouin scattering of arbitrary structured light to solve at least one of the above problems existing in the prior art.

[0007] According to one aspect of the present invention, there is provided an arbitrary structured light stimulated Brillouin scattering phase conjugation device, comprising a focusing lens, an SBS medium pool, a first pump source and a second pump source; one side of the SBS medium pool is used to receive a first pump beam from the first pump source and at least one second pump beam from the second pump source, wherein the first pump beam is a structured light; the first pump beam is incident on the SBS medium pool through the focusing lens and focused; the at least one second pump beam is incident on the SBS medium pool, crosses and interferes with the first pump beam in the SBS medium pool, so as to destroy the spatial distribution of the first pump beam through interference, so that the backward structured light Stokes wave generated after the first pump beam is focused beats with the at least one second pump beam, and the at least one second pump beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pump beam is focused is the phase conjugate light of the first pump beam.

[0008] Furthermore, the at least one second pump light beam is incident on the SBS medium pool after passing through the focusing lens.

[0009] Furthermore, when the at least one second pumping beam is directly incident on the SBS medium pool without passing through the focusing lens, the spatial distribution of the first pumping beam is simultaneously changed by the at least one second pumping beam, and the conjugate mode of the first pumping beam is amplified to achieve high-energy output of the conjugate mode.

[0010] Furthermore, the second pump beam is a Gaussian light pump beam.

[0011] Further, when the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

[0012] Furthermore, an intersection angle between the second pump light beam and the first pump light beam is less than 10°.

[0013] According to another aspect of the present invention, a phase conjugation method of stimulated Brillouin scattering of arbitrary structured light is also provided, the method comprising: a first pumping beam is incident on an SBS medium pool through a focusing lens and focused, wherein the first pumping beam is a structured light; at least one second pumping beam is incident on the SBS medium pool, and crosses and interferes with the first pumping beam in the SBS medium pool, so as to destroy the spatial distribution of the first pumping beam by interference, so that the backward structured light Stokes wave generated after the first pumping beam is focused beats with the at least one second pumping beam, and the at least one second pumping beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pumping beam is focused is the phase conjugate light of the first pumping beam. The method comprises a focusing lens, an SBS medium pool, a first pumping source and a second pumping source.

[0014] Furthermore, the at least one second pump light beam is incident on the SBS medium pool after passing through the focusing lens.

[0015] Further, when the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

[0016] Furthermore, an intersection angle between the second pump light beam and the first pump light beam is less than 10°.

[0017] The arbitrary structured light stimulated Brillouin scattering phase conjugation device and method of the present invention can inherit the self-conjugation characteristics of the traditional focused single-pump SBS structure. Compared with the prior art, the above-mentioned technology of the present invention has higher fidelity (over 95%), lower SBS threshold, and higher SBS reflectivity (R>1).

[0018] The above-mentioned arbitrary structured light stimulated Brillouin scattering phase conjugation device and method of the present invention, based on the traditional focused single-pump SBS system, uses the spatial structured light as a pump light, and simultaneously introduces another off-axis Gaussian pump with the same frequency. The two beams of light are incident into the SBS medium pool through a lens, and then cross and focus. When the two pump lights cross in the medium pool, interference occurs, destroying the spatial structure of the incident structured light pump. The focused backward structured light Stokes wave beats with the cross-Gaussian pump, and the cross-Gaussian pump energy is transferred to the Stokes wave of the structured light, and the Stokes wave of the structured light is subjected to stimulated Brillouin amplification (SBA). Accurate phase conjugation of the spatial structured light is achieved, and the reflectivity of the focused single-pump SBS system is improved.

[0019] At present, the existing PCM using traditional focused single-pump SBS to generate phase conjugate mode of spatial structure light field not only requires pump with high power density, but also cannot achieve accurate phase conjugation of arbitrary structure light field carrying OAM and other global spatial modes. According to the arbitrary structure light stimulated Brillouin scattering phase conjugation device of the embodiment of the present invention, it introduces off-axis Gaussian pump outside the focused single-pump SBS structure, firstly, changes the spatial structure of the incident structure light pump to achieve accurate phase conjugate mode generation of OAM light beam; secondly, amplifies the conjugate mode identified by the structure light pump; thirdly, compared with the traditional focused single-pump SBS structure, this structure has a lower threshold, a larger dynamic range and a higher reflectivity. In addition, using non-focused Gaussian or super-Gaussian beams that can cover the structure light distribution as off-axis pumps, uniform Brillouin amplification of the conjugate mode can be achieved, and high-fidelity phase conjugate light of the structure light can be obtained. Therefore, the embodiment of the present invention provides a high-performance SBS platform, which is of great significance to the development of high-power structure lasers, high signal-to-noise ratio microscope imaging and structure light nonlinear optics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 An exemplary structural diagram of an arbitrary structure light stimulated Brillouin scattering phase conjugation device according to an embodiment of the present invention is shown;

[0021] Figure 2 Shows Figure 1 A schematic diagram showing the principle of interference between structured light pumping and Gaussian light pumping to generate backward Stokes waves in the device shown;

[0022] Figure 3 Shows Figure 1 A schematic diagram of the working principle of the arbitrary structure light stimulated Brillouin scattering phase conjugation device 100 is shown;

[0023] Figure 4 Another exemplary structural diagram of the arbitrary structure light stimulated Brillouin scattering phase conjugation device according to an embodiment of the present invention is shown;

[0024] Figure 5 Shows Figure 4 The schematic diagram of the working principle of the arbitrary structure light stimulated Brillouin scattering phase conjugation device 100 when there is only one second pump light beam is shown;

[0025] Figure 6 Shows Figure 4 The schematic diagram of the working principle of the arbitrary structure light stimulated Brillouin scattering phase conjugation device 100 when there are two second pump beams is shown;

[0026] Figure 7 A schematic structural diagram of a preferred embodiment of an arbitrary structure light stimulated Brillouin scattering phase conjugation device according to an embodiment of the present invention is shown;

[0027] Figure 8 Schematic diagram showing phase conjugation of an OAM-carrying structured light field (LG mode);

[0028] Fig. 9 A schematic diagram showing the correlation curve between the phase conjugate light carrying the OAM structure light field (LG mode) and the pump light;

[0029] Fig.10 The SBS reflectivity and the SBS reflectivity in the conventional focused pumping and novel cross-pumping systems are shown. Schematic diagram of the relationship between mode pump energy;

[0030] Fig.11 A schematic diagram of the phase conjugation of a high-order Ince-Gauss mode structure light field that does not carry OAM is shown. DETAILED DESCRIPTION

[0031] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0032] An embodiment of the present invention provides an arbitrary structured light stimulated Brillouin scattering phase conjugation device, comprising a focusing lens, an SBS medium pool, a first pump source and a second pump source; one side of the SBS medium pool is used to receive a first pump beam from the first pump source and at least one second pump beam from the second pump source, wherein the first pump beam is structured light; the first pump beam is incident on the SBS medium pool through the focusing lens and focused; at least one second pump beam is incident on the SBS medium pool, and crosses and interferes with the first pump beam in the SBS medium pool, so as to destroy the spatial distribution of the first pump beam through interference, so that the backward structured light Stokes wave generated after the first pump beam is focused beats with at least one second pump beam, and the at least one second pump beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pump beam is focused is the phase conjugate light of the first pump beam.

[0033] In an embodiment of the present invention, the number of the at least one second pump light beam may be, for example, 1, 2 or more.

[0034] As an example, the at least one second pump light beam may be incident on the SBS medium pool after passing through a focusing lens.

[0035] Alternatively, the at least one second pump light beam may also be directly incident on the SBS medium pool without passing through the focusing lens.

[0036] The second pump beam is, for example, a Gaussian light pump beam.

[0037] As an example, when the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

[0038] The intersection angle between each second pump beam and the first pump beam is, for example, less than 10°. For example, the intersection angle between the second pump beam and the first pump beam may be 6°.

[0039] As an example, when at least one second pump beam is directly incident on the SBS medium pool without the focusing lens, the spatial distribution of the first pump beam is simultaneously changed by the at least one second pump beam to amplify the conjugate mode of the first pump beam to achieve high-energy output of the conjugate mode.

[0040] It should be noted that, in the embodiments of the present invention, the first pump source and the second pump source may also be implemented by the same pump source, for example, by splitting the light beam emitted by the same pump source or by other means to form the first and second pump beams. Similarly, the second pump source may also include multiple sub-pump sources to generate multiple second pump beams.

[0041] Principle of the Invention

[0042] In the SBS process, a frequency ω p The complex amplitude expression of the forward pump light wave can be expressed as:

[0043]

[0044] Where E p is the amplitude of the pump light wave, exp(ik p z) is the phase of the pump light wave, k p is the wave vector of the pump light, and z is the propagation distance.

[0045] A beam with frequency ω s The complex amplitude distribution of the backward Stokes scattered wave can be expressed as:

[0046]

[0047] Where E s is the amplitude of the Stokes wave, exp(-ik s z) is the phase of the Stokes wave, k s is the wave vector of the Stokes wave.

[0048] Forward pump light and backward Stokes waves Interact with each other, exciting a frequency of Ω = ω p -ω s The complex amplitude expression of the forward sound wave is:

[0049]

[0050] In the formula is the complex amplitude of the acoustic wave field, ρ is the amplitude of the acoustic wave field, exp(iqz) is the acoustic wave phase, and q represents the wave vector of the acoustic wave field.

[0051] When the photoacoustic dispersion relation meets the phase matching condition:

[0052] q(Ω)=k p (ω p )+k s (ω s ) (4)

[0053] The amplitude of the sound wave can be written as:

[0054]

[0055] Among them, k in formula (4) p (ω p) are the frequencies in the medium and p is the wave vector of the pump light wave, κ is the coupling coefficient, and the symbol * represents the complex conjugate of the complex amplitude of the light field.

[0056] In the traditional focused single-pump SBS structure, the pump light wave energy is transferred to the Stokes wave through the medium of acoustic wave, resulting in the amplification of the Stokes wave. The maximum Brillouin gain of the Stokes scattered wave mainly depends on the precise overlap of the intensity distribution of the pump light wave and the Stokes scattered wave, where the light wave that is accurately phase-conjugated with the pump light wave is amplified with high gain, while the remaining scattered waves are suppressed due to their low gain. The complex amplitude of the Stokes scattered wave can be expressed as: Represents the complex conjugate of the complex amplitude of the pump light wave.

[0057] In addition, when the incident pump light is a structured light carrying OAM, since the OAM light field modes of opposite chirality have the same lateral intensity distribution, such as the Laguerre-Gaussian (LG) modes with topological charge of +1 and -1, they can completely overlap with the pump light, and their Stokes waves will obtain the maximum gain and be selected from the noise. Therefore, the Stokes wave exhibits a superposition state of the OAM modes of opposite chirality, so the traditional focused single-pump SBS geometry cannot produce accurate phase conjugation of the OAM structured light.

[0058] Introducing an off-axis Gaussian pump into the traditional focused single-pump SBS structure, the complex amplitude of a structured light pump carrying OAM can be expressed as:

[0059]

[0060] Where E p1 is the amplitude of structured light pumping, is the spiral phase term of structured light pumping, l is the topological charge, exp(ik p1 z) is the propagation phase, k p1 represents the wave vector of structured light pumping. The complex amplitude of off-axis Gaussian pumping can be expressed as:

[0061]

[0062] in is the amplitude of the off-axis Gaussian pump, exp(ik p2 z) is the propagation phase, k p2 represents the wave vector of Gaussian pumping. The two pumping lights cross-interfere and form interference fringes, whose complex amplitude can be expressed as:

[0063]

[0064] In the formula, the symbol ∝ indicates a proportional relationship. At the intersection of the two pump light beams, an interference field with a complex amplitude of u is formed, and the structure pump light E p1 The spatial distribution of Stokes waves with the same chiral OAM mode can have the maximum gain. This can prevent Stokes waves with the same spatial distribution and opposite chirality from being amplified at the same time, thereby achieving accurate phase conjugation of the OAM mode. Stokes waves excited by noise Beat frequency with Gaussian pump to produce sound field This results in energy transfer from the crossed Gaussian pump to the structured light pump. This process can be regarded as a non-collinear double-ended SBS, which realizes the Stokes wave The stimulated Brillouin amplification (SBA) improves the reflectivity of the structured light Stokes wave.

[0065] Exemplary device 1

[0066] like Figure 1 As shown, in one example, the arbitrary structured light stimulated Brillouin scattering phase conjugation device 100 includes a focusing lens 1 , an SBS medium pool 2 , a first pump source 3 and a second pump source 4 .

[0067] One side of the SBS medium pool 2 is used to receive a first pumping beam from a first pumping source 3 and at least one second pumping beam from a second pumping source 4 , wherein the first pumping beam is structured light.

[0068] In the arbitrary structured light stimulated Brillouin scattering phase conjugation device 100 , the first pumping light beam and the second pumping light beam are both incident on the SBS medium pool through the focusing lens 1 and focused.

[0069] In the SBS medium pool, the first pump beam and the second pump beam cross and interfere with each other, and the spatial distribution of the first pump beam is destroyed by interference, so that the backward structured light Stokes wave generated after the first pump beam is focused beats with the second pump beam, and at least one second pump beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pump beam is focused is the phase conjugate light of the first pump beam.

[0070] According to the arbitrary structured light stimulated Brillouin scattering phase conjugation device 100 of this embodiment, a low-threshold enhanced SBS scheme with cross-pump focusing is provided, which can perform phase conjugation on arbitrary structured light. Based on the traditional focused single-pump SBS structure, a beam of structured light or other global spatial mode light carrying OAM (as an example of the first pump beam) is incident at one end of the medium pool, and one or more off-axis Gaussian lights (as an example of the second pump beam) are introduced at the same time. The two pump lights are focused and incident into the medium pool to cross and form interference, and the crossing angle θ<10°.

[0071] As an example, the first pump beam can adopt any mode structured light, such as various vortex modes of OAM, high-order global modes without OAM, etc., which can be perfectly conjugated in amplitude and phase.

[0072] This embodiment can inherit the self-conjugation characteristics of the traditional focused single-pump SBS structure. Compared with the traditional method, this device has higher fidelity (over 95%), lower SBS threshold, and higher SBS reflectivity (R>1).

[0073] Based on the traditional focused single-pump SBS system, the spatial structured light is used as a pump light, and another off-axis Gaussian pump with the same frequency is introduced at the same time. The two beams of light are incident into the SBS medium pool through the lens, and then cross and focus. When the two pump lights cross in the medium pool, interference occurs, destroying the spatial structure of the incident structured light pump. The Stokes wave of the focused backward structured light beats with the cross-Gaussian pump, and the cross-Gaussian pump energy is transferred to the Stokes wave of the structured light, and the Stokes wave of the structured light is stimulated Brillouin amplification (SBA). Accurate phase conjugation of the spatial structured light is achieved, and the reflectivity of the focused single-pump SBS system is improved.

[0074] At present, the existing PCM using traditional focused single-pump SBS to generate phase conjugate mode of spatial structure light field not only requires pump with high power density, but also cannot achieve accurate phase conjugation of arbitrary structure light field carrying OAM and other global spatial modes. According to the arbitrary structure light stimulated Brillouin scattering phase conjugation device of the embodiment of the present invention, it introduces off-axis Gaussian pump outside the focused single-pump SBS structure, firstly, changes the spatial structure of the incident structure light pump, and realizes the accurate phase conjugate mode generation of OAM light beam; secondly, it amplifies the conjugate mode identified by the structure light pump; thirdly, compared with the traditional focused single-pump SBS structure, this structure has a lower threshold, a larger dynamic range and a higher reflectivity. In addition, using non-focused Gaussian or super-Gaussian beams that can cover the structure light distribution as off-axis pumps, uniform Brillouin amplification of the conjugate mode can be achieved, and high-fidelity phase conjugate light of the structure light can be obtained. Therefore, the embodiment of the present invention provides a high-performance SBS platform, which is of great significance to the development of high-power structure lasers, high signal-to-noise ratio microscope imaging and structure light nonlinear optics.

[0075] Figure 2 and Figure 3 The working principle of the above-mentioned arbitrary structure light stimulated Brillouin scattering phase conjugation device 100 is shown. Figure 2 As shown, a beam of structured light pumps E p1 (as the first pump beam) is horizontally incident on the SBS medium pool 2 through the focusing lens 1 and focused. Another Gaussian light pumps E p2 (As the second pump beam) passes through the focusing lens 1 and then is incident obliquely onto the SBS medium pool 2, where it intersects with the structured light pump and then focuses. p1 With Gaussian light pumping E p2 The crossing angle is, for example, θ=6° or θ≈6° (θ<10°), forming interference fringes. The interference destroys the spatial distribution of the incident structured light pump.

[0076] See also Figure 3 , structured light pumping E p1 Stokes wave E excited from noise s1 , and through the sound field Selective amplification of structured light pumping with changed spatial distribution p1 , generating the phase conjugate light of the incident structured light field Stokes wave E s1 Propagates in the opposite direction of the incident structured light pump and crosses the incident Gaussian light pump E p2 Beat frequency to generate another sound field This causes energy to be transferred from the Gaussian pump to the Stokes wave E s1This process can be regarded as a non-collinear double-ended SBS, which realizes the transmission of Stokes wave E s1 SBA. Simultaneous Cross-Gaussian Pumping E p2 Through focusing, the sound field will also be aroused in the noise The generated backward Stokes wave E s2 The beat frequency of the incident structured light pump forms an acoustic field The acoustic fields ρ2 and ρ4 cause the loss of energy of the two pump beams and the Stokes wave E s1 The increase and loss of production efficiency.

[0077] Exemplary Device 2

[0078] like Figure 4 As shown, the arbitrary structure light stimulated Brillouin scattering phase conjugation device 400 includes a focusing lens 1 , an SBS medium pool 2 , a first pump source 3 and a second pump source 4 .

[0079] One side of the SBS medium pool 2 is used to receive a first pumping beam from a first pumping source 3 and at least one second pumping beam from a second pumping source 4 , wherein the first pumping beam is structured light.

[0080] In the arbitrary structured light stimulated Brillouin scattering phase conjugation device 400, the first pump beam is incident on the SBS medium pool 2 through the focusing lens 1 and is focused, while the second pump beam is directly incident on the SBS medium pool 22 without passing through the focusing lens 21, and the second pump beam is not focused.

[0081] In the SBS medium pool 2, the first pump beam and the second pump beam cross and interfere with each other, and the spatial distribution of the first pump beam is destroyed by interference, so that the backward structured light Stokes wave generated after the first pump beam is focused beats with the second pump beam, and at least one second pump beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein, the backward structured light Stokes wave generated after the first pump beam is focused is the phase conjugate light of the first pump beam.

[0082] Figure 5 The working principle of the arbitrary structured light stimulated Brillouin scattering phase conjugation device 400 is shown when there is only one second pumping light beam.

[0083] like Figure 5 As shown in the figure, the incident focused Gaussian pump (as the second pump beam) is changed to a non-focused Gaussian pump, which is incident on the medium pool 2 and cross-interferes with the structured light pump. At this time, only two acoustic fields ρ1 and ρ2 are generated. For a weak Stokes signal and un-evacuated cross-pumping, an approximate expression for the output intensity of the Stokes wave under the action of two acoustic fields can be obtained:

[0084] I s0 exp[g(0°)I p1 L1]·[1+exp[g(θ)I p2 L2] (9)

[0085] The first term in equation (9) represents the exponentially growing Stokes wave generated by the on-axis structured light pump noise, where I s0 represents the effective Stokes wave input intensity, I s0 ≈10 -12 I p1 I p1 represents the intensity of the structured light pump at the beam waist, L1 is the focusing SBS interaction length, L1≈2z R (z R is the Rayleigh length), g(0°) represents the maximum SBS gain along the axial direction θ = 0°. The second term in the square brackets in equation (9) represents the SBA process of the Stokes wave excited by the off-axis Gaussian beam to the structured light pump, where g(θ) represents the Brillouin gain along the θ direction, and for θ < 10°, g(θ) ≈ g(0°); I p2 represents the intensity of Gaussian light pumping, L2 is the SBA interaction length, which can be calculated by L2≈d / sin(θ), and d is the diameter of the Gaussian pump beam.

[0086] Figure 6 The working principle of the arbitrary structured light stimulated Brillouin scattering phase conjugation device 400 is shown in the case where there are two second pumping light beams.

[0087] like Figure 6 As shown, in order to achieve high-energy output of the conjugated mode, two unfocused Gaussian pumps (as at least one second pump beam) are introduced symmetrically into the SBS medium pool at an angle θ, as shown in FIG. Figure 6 As shown in Figure 2, the two pump beams simultaneously change the pump distribution of the structured light and amplify the conjugate mode of the structured light. In addition, by further expanding the structure to a multi-pump beam combination system, higher intensity phase conjugate light can be generated.

[0088] Exemplary Methods

[0089] An embodiment of the present invention also provides a phase conjugation method for stimulated Brillouin scattering of arbitrary structured light, the method comprising: a first pumping light beam is incident on an SBS medium pool through a focusing lens and focused, wherein the first pumping light beam is structured light; at least one second pumping light beam is incident on the SBS medium pool, and crosses and interferes with the first pumping light beam in the SBS medium pool, so as to destroy the spatial distribution of the first pumping light beam through interference, so that the backward structured light Stokes wave generated after the first pumping light beam is focused beats with the at least one second pumping light beam, and the at least one second pumping light beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; wherein the backward structured light Stokes wave generated after the first pumping light beam is focused is the phase conjugate light of the first pumping light beam.

[0090] As an example, at least one second pump light beam is incident on the SBS medium pool after passing through a focusing lens.

[0091] As an example, the second pump beam is a Gaussian pump beam.

[0092] As an example, when the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

[0093] As an example, the crossing angle between the second pump beam and the first pump beam is less than 10°, for example, may be 6°.

[0094] It should be noted that the above arbitrary structured light stimulated Brillouin scattering phase conjugation method can be combined with the above Figure 1-6 Similar processing and functions of the described arbitrary structured light stimulated Brillouin scattering phase conjugation device are not repeated here.

[0095] Preferred Embodiments

[0096] Next, combine Figure 7 A preferred embodiment of the present invention is described. Figure 7 As shown, in this embodiment, the arbitrary structure light stimulated Brillouin scattering phase conjugation device includes a first reflector 71, a phase-type spatial light modulator 72, a second reflector 73, a first lens 74, a polarization beam splitter (PBS) 75, a quarter wave plate (QWP) 76, a second lens 77, an SBS medium pool 78, a pinhole 79 and a CCD 70. In addition, Figure 7 The arbitrary structured light stimulated Brillouin scattering phase conjugation device shown also includes a first pump source and a second pump source. In this embodiment, the first pump source and the second pump source are implemented by the same pump source (not shown in the figure).

[0097] In this embodiment, complex amplitude modulation technology is used to load complex amplitude masks of structured light carrying OAM and some other global spatial mode lights on the spatial light modulator. After the incident light is modulated by the complex amplitude mask with a blazed grating, the diffraction efficiency is controlled by controlling the phase depth of the blazed grating, so that the first-order diffracted light is a structured light of different spatial modes, and the zero-order is a Gaussian-like beam. The two beams of light are focused into the SBS medium pool through a lens as pump light, and the grating constant is controlled so that the two beams of light cross and interfere with each other in the medium pool before focusing. The subsequent Stokes wave caused by noise propagates in reverse and beats with the incident Gaussian pump light, resulting in energy transfer from the Gaussian pump to the Stokes wave, realizing the stimulated Brillouin amplification of the Stokes wave. Due to the interference of the two pump lights, the lateral distribution of the incident structured light is destroyed, resulting in that when the incident light is a structured light carrying OAM, a single mode of phase conjugation of the pump light can be selected from the degenerate OAM mode.

[0098] like Figure 7 As shown, first, the horizontally polarized plane wave (i.e., the light output by the above-mentioned pump source) is reflected by the first reflector 71 to the surface of the phase-type spatial light modulator 72, and the phase-type spatial light modulator 72 is loaded with the Fourier spectrum complex amplitude mask of the arbitrary mode spatial structured light with the blazed grating. The first-order diffracted light and the zero-order light reflected by the surface of the phase-type spatial light modulator 72 are the structured light pump and the Gaussian-like pump, respectively. The two beams of light are reflected by the second reflector 73 to the first lens 74 (as an example of a focusing lens) for inverse Fourier transformation. The focus of the first lens 74 obtains the arbitrary mode spatial structured light (as an example of the first pump beam) and a Gaussian-like beam (as an example of the second pump beam), which are diffracted and pass through the polarization beam splitter (PBS) 75 and the quarter wave plate (QWP) 76 at the same time. The two beams are focused by the second lens 77 into the SBS medium pool 78, cross and interfere with each other before the focusing point. After the two beams of light undergo the SBS phenomenon in the SBS medium pool 78, backward Stokes light is generated, which completely overlaps with the wavefronts of the two pump beams and propagates in the opposite direction. After passing through the device 76, the two Stokes lights are reflected by the device 75 to the small hole 79, and the phase conjugate light of the spatial structure light field is extracted and diffracted to the surface of the CCD 70 to be recorded.

[0099] Figure 8 A schematic diagram of the phase conjugation of an OAM structured light field (LG mode) is shown, that is, when the incident light field is a structured light field carrying OAM, taking an LG beam as an example, the intensity distributions of four LG mode pump lights are given respectively (as shown in the "experimental pumping" in the figure), and the traditional focusing SBS reflected light exhibits a petal-shaped degenerate OAM mode (as shown in the "traditional focusing SBS" in the figure). The accurate phase conjugation of the pump light can be obtained by using cross-pump focusing SBS (as shown in the "cross-pump focusing SBS" in the figure).

[0100] Combination Fig. 9 , under the cross-pump focusing SBS system, the correlation curve between the phase conjugate wave, i.e., the Stokes wave, generated by the LG beam carrying OAM and the pump light is given. It can be seen that this system can obtain high-fidelity structured light phase conjugate waves with a fidelity of more than 95%.

[0101] Fig.10 The SBS reflectivity and structured light pump energy (in terms of For example, the relationship between the SBS threshold energy and the LG pump energy is shown in Figure 2. For a conventional focused single pump system, the SBS threshold energy is about 40 μJ, and for a LG pump of 72 μJ, the maximum reflectivity obtained is 23%. However, under the cross-pump system, the reflectivity is greatly improved and the threshold is significantly reduced. In particular, when the LG pump energy E pin When the energy is less than the threshold of conventional pumping, a reflectivity of more than 50% is achieved due to the amplification effect of Gaussian pumping. Under the existing experimental conditions, the maximum reflectivity of 118% was achieved at 4μJ, the threshold was reduced by more than ten times, and the dynamic pump energy range was expanded accordingly. In fact, when the pump energy is less than 4μJ, the output Stokes wave can still be observed with the naked eye, but it cannot be accurately measured due to the limitation of the measurement range of the energy meter. In addition, as mentioned above, these key performances can be further improved by using unfocused Gaussian pumping.

[0102] In addition, see Fig.11 It can be seen that when the incident pump is a high-order Ince-Gaussian beam that does not carry OAM, the phase conjugation of the pump light can be achieved under the traditional focused single-pump SBS, but the experimental results show low reflectivity and fidelity. However, using the cross-pump focused SBS method, the energy of the cross-pump is transferred to the pump structured light, and after the SBA process, high-fidelity, high-reflectivity phase conjugated light can be obtained.

[0103] Those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments is meant to be within the scope of the present invention and to form different embodiments. In addition, some of the embodiments described herein are described as a combination of methods or method elements that can be implemented by a processor of a computer system or by other devices that perform the functions. Therefore, a processor with necessary instructions for implementing the method or method elements forms a device for implementing the method or method elements. In addition, the elements described herein of the device embodiment are examples of devices that are used to implement the functions performed by the elements for the purpose of implementing the invention.

[0104] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0105] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is primarily selected for readability and instructional purposes, rather than for explaining or limiting the subject matter of the present invention.

Claims

1. An arbitrary structure light stimulated Brillouin scattering phase conjugation device, characterized in that: It includes a focusing lens, an SBS medium pool, a first pump source and a second pump source; One side of the SBS medium pool is used to receive a first pumping beam from the first pumping source and at least one second pumping beam from the second pumping source, wherein the first pumping beam is a structured light; and the second pumping beam is a Gaussian beam; The first pump light beam is incident on the SBS medium pool through the focusing lens and focused; The at least one second pumping beam is incident on the SBS medium pool, and crosses and interferes with the first pumping beam in the SBS medium pool, so as to destroy the spatial distribution of the first pumping beam by interference, so that the backward structured light Stokes wave generated after the first pumping beam is focused beats with the at least one second pumping beam, so that the at least one second pumping beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; The backward structured light Stokes wave generated after the first pump light beam is focused is the phase conjugate light of the first pump light beam.

2. The arbitrary structure light stimulated Brillouin scattering phase conjugation device according to claim 1, characterized in that: The at least one second pump light beam is incident on the SBS medium pool after passing through the focusing lens.

3. The arbitrary structure light high performance stimulated Brillouin scattering phase conjugation device according to claim 1, characterized in that: When the at least one second pumping beam is directly incident on the SBS medium pool without passing through the focusing lens, the spatial distribution of the first pumping beam is simultaneously changed by the at least one second pumping beam, and the conjugate mode of the first pumping beam is amplified to achieve high-energy output of the conjugate mode.

4. The arbitrary structure light high performance stimulated Brillouin scattering phase conjugation device according to claim 1, characterized in that: The second pump beam is a Gaussian pump beam.

5. The arbitrary structure light high performance stimulated Brillouin scattering phase conjugation device according to claim 1, characterized in that: When the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

6. The arbitrary structure light high performance stimulated Brillouin scattering phase conjugation device according to any one of claims 1 to 5, characterized in that: The intersection angle between the second pump beam and the first pump beam is less than.

7. A phase conjugation method for stimulated Brillouin scattering of arbitrary structured light, characterized in that: The method is implemented based on an arbitrary structure light stimulated Brillouin scattering phase conjugation device, and the arbitrary structure light stimulated Brillouin scattering phase conjugation device includes a focusing lens, an SBS medium pool, a first pump source and a second pump source; The method comprises: The first pump beam is incident on the SBS medium pool through a focusing lens and focused, wherein the first pump beam is structured light; At least one second pumping beam is incident on the SBS medium pool, and crosses and interferes with the first pumping beam in the SBS medium pool, so as to destroy the spatial distribution of the first pumping beam by interference, so that the backward structured light Stokes wave generated after the first pumping beam is focused beats with the at least one second pumping beam, so that the at least one second pumping beam performs stimulated Brillouin amplification on the backward structured light Stokes wave; the second pumping beam is a Gaussian beam; The backward structured light Stokes wave generated after the first pump light beam is focused is the phase conjugate light of the first pump light beam.

8. The method for phase conjugation of stimulated Brillouin scattering of arbitrary structured light according to claim 7, characterized in that: The at least one second pump light beam is incident on the SBS medium pool after passing through the focusing lens.

9. The arbitrary structure light high performance stimulated Brillouin scattering phase conjugation method according to claim 7, characterized in that: When the number of the at least one second pumping light beam is greater than 1, the at least one second pumping light beam is symmetrically and obliquely incident on the SBS medium pool.

10. The arbitrary structured light high performance stimulated Brillouin scattering phase conjugation method according to any one of claims 7 to 9, characterized in that: The intersection angle between the second pump beam and the first pump beam is less than.

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