Phase resolution Brillouin spectrum system

Abstract

The invention provides a phase-resolved Brillouin spectrum system, and the system comprises a microwave pulse signal generation device which is configured to generate a first microwave pulse signal and a second microwave pulse signal; the quasi-particle excitation device is configured to bear a sample and absorb the first microwave pulse signal so as to excite quasi-particles in the local part of the sample; the laser light source is configured to generate laser, so that the laser is focused on the target position of the sample to generate Brillouin scattering with the quasi-particles, and Brillouin scattering light is generated; wherein the target position is adjustable; the electro-optical modulator is configured to modulate the phase of the laser to generate frequency shift reference light under the driving of the second microwave pulse signal, and the frequency shift reference light interferes with the Brillouin scattering light; wherein the phase resolution Brillouin spectrum is measured by adjusting the target position.

Description

Technical Field

[0001] The present disclosure relates to the technical field of Brillouin spectroscopy testing, and in particular to a phase-resolved Brillouin spectroscopy system. Background Art

[0002] With the rapid development of technology, Brillouin spectroscopy has been widely used to measure the properties of acoustic waves in materials and spin waves in magnetic materials, including confined acoustic phonons, magnon-phonon coupling, Bose-Einstein condensation of magnons, the formation of spin wave envelope solitons, and Dzyaloshinskii-Moriya interaction. In addition to traditional frequency analysis, Brillouin spectrometers can also achieve wave vector, time and space resolution, as well as temperature, magnetic field and pressure-dependent Brillouin spectroscopy measurements, which are suitable for studying various materials from bulk to nanoscale. Combined with wave vector resolution technology, Brillouin spectrometers can measure the dispersion of phonons and magnons, which is very important for understanding the properties of electrons, phonons and magnons in materials. Time resolution technology can analyze the propagation and relaxation characteristics of spin waves, while space resolution technology can further derive the spatial distribution of spin waves during propagation.

[0003] However, time-resolved and spatially-resolved techniques are based on simple counting of inelastically scattered photons and are only sensitive to the intensity of the spin wave, so only the shape of the spin wave pulse can be studied without obtaining phase information about the magnetic excitation. Although all nonlinear effects can be clearly observed through changes in shape and intensity, the lack of phase information also leads to an incomplete description of the underlying physical processes. Therefore, there is a need to develop phase-resolved Brillouin spectroscopy systems. Summary of the invention

[0004] In view of this, the present disclosure provides a phase-resolved Brillouin spectroscopy system for at least partially solving the above technical problems.

[0005] An embodiment of the present disclosure provides a phase-resolved Brillouin spectroscopy system, comprising: a microwave pulse signal generating device, configured to generate a first microwave pulse signal and a second microwave pulse signal; a quasiparticle excitation device, configured to carry a sample and absorb the first microwave pulse signal to locally excite quasiparticles in the sample; a laser light source, configured to generate laser light so that the laser light is focused on a target position of the sample to cause Brillouin scattering with the quasiparticles to generate Brillouin scattered light; wherein the target position is adjustable; an electro-optic modulator, configured to modulate the phase of the laser light under the drive of the second microwave pulse signal to generate a frequency-shifted reference light, the frequency-shifted reference light interfering with the Brillouin scattered light; wherein the phase-resolved Brillouin spectroscopy is measured by adjusting the target position.

[0006] According to an embodiment of the present disclosure, a microwave pulse signal generating device includes: a pulse generator, configured to generate a pulse signal; a microwave source, configured to generate a continuous microwave signal and convert the continuous microwave signal into an initial microwave pulse signal under the action of a received pulse signal; and a power splitter, configured to split the initial microwave pulse signal into two paths to obtain a first microwave pulse signal and a second microwave pulse signal.

[0007] According to an embodiment of the present disclosure, the microwave pulse signal generating device further includes: an attenuator configured to adjust the intensity of the second microwave pulse signal.

[0008] According to an embodiment of the present disclosure, the microwave pulse signal generating device further includes: a phase shifter configured to adjust the phase of the second microwave pulse signal.

[0009] According to an embodiment of the present disclosure, the system further includes: a beam splitter configured to reflect the laser light and the frequency-shifted reference light, and to transmit the frequency-shifted reference light and the Brillouin scattered light.

[0010] According to an embodiment of the present disclosure, the system further includes: a polarizer configured to adjust the relative intensities of the frequency-shifted reference light and the Brillouin scattered light to optimize interference between the frequency-shifted reference light and the Brillouin scattered light.

[0011] According to an embodiment of the present disclosure, the system further includes: a Fabry-Perot interferometer configured to analyze the interference result of the frequency-shifted reference light and the Brillouin scattered light, and output an interference signal of a preset frequency.

[0012] According to an embodiment of the present disclosure, the frequency-shifted reference light and the Brillouin scattered light have the same frequency.

[0013] According to an embodiment of the present disclosure, the quasiparticle includes an acoustic phonon or a magnon; when the quasiparticle is a magnon, the sample is a magnetic material, and the quasiparticle excitation device is a resonant cavity.

[0014] According to an embodiment of the present disclosure, when the quasiparticle is a magnon, the system further includes: a magnetic field generating device configured to apply a magnetic field to the magnetic material on the surface of the resonant cavity.

[0015] According to the phase-resolved Brillouin spectroscopy system of the embodiment of the present disclosure, the laser light source generates a laser focused on the target position of the sample and generates Brillouin scattering with the quasiparticles to obtain Brillouin scattered light. The microwave pulse signal passes through the electro-optic modulator to detune a small portion of the laser light and generate sidebands, which serve as frequency-shifted reference light. The Brillouin scattered light and the reflected frequency-shifted reference light interfere with each other, and the two enter the Fabry-Perot interferometer for analysis to obtain the intensity-frequency relationship. By moving the target position, the intensity, frequency, space and phase relationships can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic diagram of a connection structure of a phase-resolved Brillouin spectroscopy system according to an embodiment of the present disclosure is shown;

[0018] Figure 2 The structure of a phase-resolved Brillouin spectroscopy system according to another embodiment of the present disclosure is schematically shown.

[0019] Description of reference numerals:

[0020] 10-microwave signal generating device, 11-pulse generator, 12-microwave source, 13-power beam splitter, 14-attenuator, 15-phase shifter, 16-switch, 20-quasiparticle excitation device, 30-laser light source, 40-electro-optic modulator, 50-beam splitter, 60-polarizer, 70-Fabry-Perot interferometer. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0022] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0023] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0024] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] The embodiments of the present disclosure provide an easy-to-build, low-cost phase-resolved Brillouin spectroscopy system that can study the formation and dynamics of coherent states in magnon gases and two-dimensional spin wave phase profiles, etc. The following is an introduction in conjunction with specific embodiments.

[0026] Figure 1 The figure schematically shows a connection structure diagram of a phase-resolved Brillouin spectroscopy system according to an embodiment of the present disclosure.

[0027] like Figure 1 As shown, the phase-resolved Brillouin spectroscopy system may include: a microwave pulse signal generating device 10 , a quasiparticle excitation device 20 , a laser light source 30 and an electro-optic modulator 40 .

[0028] The microwave pulse signal generating device 10 is configured to generate a first microwave pulse signal and a second microwave pulse signal.

[0029] The quasiparticle excitation device 20 is configured to carry the sample and absorb the first microwave pulse signal to excite quasiparticles locally in the sample. Specifically, the frequency of the first microwave pulse signal received by the quasiparticle excitation device 20 is equal to the resonant frequency of the quasiparticle excitation device 20, so that the quasiparticle excitation device 20 can absorb the microwave pulse signal to the maximum extent to excite quasiparticles locally in the sample. The wave propagation corresponding to the quasiparticle reaches the laser spot position, and the quasiparticle undergoes Brillouin scattering with the photons of the incident laser to generate Brillouin scattered light.

[0030] The laser light source 30 is configured to generate laser light of a certain energy (frequency), which is focused on a target position of the sample and generates Brillouin scattering with the quasiparticles to generate Brillouin scattered light, wherein the target position is adjustable.

[0031] The electro-optic modulator 40 is configured to modulate the phase of the laser to generate a frequency-shifted reference light under the drive of the second microwave pulse signal, and the frequency-shifted reference light interferes with the Brillouin scattered light.

[0032] According to the embodiments of the present disclosure, by adjusting the target position, Brillouin scattered light corresponding to different positions can be generated, and the Brillouin scattered light corresponding to each target position interferes with the frequency-shifted reference light to achieve phase-resolved Brillouin spectrum measurement.

[0033] Figure 2 The structure of a phase-resolved Brillouin spectroscopy system according to another embodiment of the present disclosure is schematically shown.

[0034] like Figure 2 As shown, based on the above embodiment, the microwave pulse signal generating device 10 may include: a pulse generator 11 , a microwave source 12 and a power beam splitter 13 .

[0035] The pulse generator 11 is configured to generate a pulse signal and input the pulse signal to the microwave source 12. For example, the pulse generator 11 can generate a pulse signal with a pulse period of T and a pulse width of Δt.

[0036] The microwave source 12 is configured to generate a continuous microwave signal and convert the continuous microwave signal into an initial microwave pulse signal under the action of the received pulse signal.

[0037] The power beam splitter 13 is configured to split the initial microwave pulse signal into two paths to obtain a first microwave pulse signal and a second microwave pulse signal.

[0038] Furthermore, the microwave pulse signal generating device 10 may further include a switch 16, which includes a first switch 161 and a second switch 162. The first switch 161 may be used to control the opening and closing of the channel corresponding to the first microwave pulse signal, and the second switch 162 may be used to control the opening and closing of the channel corresponding to the second microwave pulse signal.

[0039] Continue reading Figure 2 On the basis of the above embodiment, the microwave pulse signal generating device 10 may further include: an attenuator 14 configured to adjust the intensity of the second microwave pulse signal.

[0040] Continue reading Figure 2 On the basis of the above embodiment, the microwave pulse signal generating device 10 may further include: a phase shifter 15 configured to adjust the phase of the second microwave pulse signal.

[0041] According to an embodiment of the present disclosure, the second microwave pulse signal passes through the attenuator 14, the phase shifter 15 and the electro-optical modulator 40 to detune a small part of the laser and generate sidebands as frequency-shifted reference light, whose intensity and phase are adjusted by the attenuator and the phase shifter respectively.

[0042] Continue reading Figure 2 , based on the above embodiment, the phase-resolved Brillouin spectroscopy system further includes:

[0043] The beam splitter 50 is configured to reflect the laser light and the frequency-shifted reference light, and transmit the frequency-shifted reference light and the Brillouin scattered light, so as to focus the laser light on the target position of the sample by reflecting the laser light.

[0044] Continue reading Figure 2 , based on the above embodiment, the phase-resolved Brillouin spectroscopy system further includes:

[0045] The polarizer 60 is configured to adjust the relative intensity of the frequency-shifted reference light and the Brillouin scattered light to optimize the interference between the frequency-shifted reference light and the Brillouin scattered light. That is, the polarizer 60 can make the frequency-shifted reference light and the Brillouin scattered light interfere better.

[0046] Continue reading Figure 2 , based on the above embodiment, the phase-resolved Brillouin spectroscopy system further includes:

[0047] The Fabry-Perot interferometer 70 is configured to analyze the interference result between the frequency-shifted reference light and the Brillouin scattered light, and output an interference signal of a preset frequency.

[0048] On the basis of the above embodiment, the frequency-shifted reference light and the Brillouin scattered light have the same frequency to ensure time coherence.

[0049] On the basis of the above-mentioned embodiment, the quasiparticles include acoustic phonons or magnons; when the quasiparticles are magnons, the sample is a magnetic material, and the quasiparticle excitation device 20 is a resonant cavity.

[0050] Furthermore, when the quasiparticle is a magnon, the phase-resolved Brillouin spectroscopy system further includes:

[0051] The magnetic field generating device is configured to apply a magnetic field to the magnetic material on the surface of the resonant cavity to study the phase-related properties of the magnetic excitation.

[0052] In order to more clearly illustrate the phase-resolved Brillouin spectroscopy system provided by the embodiments of the present disclosure, a specific example is listed below for illustration.

[0053] In this example, the wavelength of the spin wave generated by external excitation in yttrium iron garnet (YIG) is obtained using the phase-resolved Brillouin spectroscopy system provided by the embodiment of the present disclosure. A reference light with a fixed phase is used to interfere with the inelastic scattered light, and the interference signal will contain the amplitude and phase information of the propagated spin wave. The pulse generator 11 generates a pulse signal with a pulse width of 1 μs and a pulse period of 10 μs, and inputs the pulse signal into the microwave source 12 to convert the continuous microwave signal into a microwave pulse signal. The microwave pulse signal is divided into two paths by the power beam splitter 13, one of which is used to excite spin waves on the sample surface. YIG is connected to the power beam splitter 13 through a quasiparticle excitation device 20 (a resonant cavity such as an antenna or a coplanar waveguide), and the frequency of the microwave pulse signal is equal to the resonant frequency of the quasiparticle excitation device 20 to ensure that the microwave signal is absorbed by the resonant cavity to the greatest extent, thereby locally exciting spin waves in YIG. When the locally excited spin wave in YIG propagates to the laser spot position and undergoes Brillouin scattering with the incident photon, Brillouin scattered light is generated. Another microwave pulse signal is used to detune a small portion of the laser through the attenuator 14, the phase shifter 15, and the electro-optic modulator 40 to generate a sideband as a frequency-shifted reference light. The Brillouin scattered light and the reflected frequency-shifted reference light will interfere, and after passing through the beam splitter 50 and the polarizer 60, the two enter the Fabry-Perot interferometer 70.

[0054] In order to observe the interference signal, three conditions must be met between the frequency-shifted reference light and the Brillouin scattered light: First, the frequency-shifted reference light must have the same frequency as the Brillouin scattered light to ensure temporal coherence. Since the electro-optic modulator 40 and the resonant cavity such as the antenna or coplanar waveguide used to excite the spin wave are driven by the same microwave source 12, this ensures the coherence of the frequency-shifted reference light and the Brillouin scattered light. Depending on the external pump frequency, a small part of the laser will undergo red (blue) shift, generating sidebands. For the generation of frequency-shifted reference light by modulating the phase of the incident laser using the electro-optic modulator 40, since the selected modulation amplitude is very small, the intensity of the frequency-shifted reference light is at the same order of magnitude as the intensity of the Brillouin scattered light scattered by the spin wave. However, the intensity of the frequency-shifted reference light and the Brillouin scattered light is many orders of magnitude lower than the intensity of the total laser, so second-order effects such as the Brillouin scattering of the frequency-shifted reference light by the spin wave can be ignored. Second, the intensity of the frequency-shifted reference light must be comparable to the intensity of the Brillouin scattered light to obtain the maximum interference contrast. The intensity of the frequency-shifted reference light can be adjusted to match the intensity of the Brillouin scattered light using a phase-stable, tunable attenuator 14. The phase of the frequency-shifted reference light can be adjusted using an adjustable phase shifter 15. Third, in order for the two beams of light to interfere, they need to have the same polarization direction. The polarization of the light inelastically scattered from the spin wave (Brillouin scattered light) is rotated 90° relative to the incident light, while the frequency-shifted reference light is simply reflected from the sample surface, thus maintaining the polarization of the incident light. A polarizer 60 with a polarization plane orientation between 0°-90° is placed in front of the Fabry-Perot interferometer 70. By changing the orientation of the polarizer 60, the relative intensity of the two beams of light can be adjusted to optimize the interference between the two. When only switch 162 is closed, the signal detected at the Fabry-Perot interferometer 70 is the frequency-shifted reference light signal; when only switch 161 is closed, the signal detected at the Fabry-Perot interferometer 120 is the Brillouin scattered light signal; when both switches 161 and 162 are closed, the signal detected at the Fabry-Perot interferometer 70 is the interference signal of the frequency-shifted reference light and the Brillouin scattered light.

[0055] By fixing the phase of the frequency-shifted reference light, moving the target position, and measuring the interference signal at different positions in space, we can see that its intensity oscillates periodically. The maximum intensity corresponds to constructive interference, and the minimum intensity corresponds to destructive interference. The distance between two adjacent maximum intensity points corresponds to the wavelength of the excited spin wave.

[0056] The phase-resolved Brillouin spectroscopy system provided by the embodiment of the present disclosure can be simply and conveniently implemented and operated, and the cost required to build the phase-resolved Brillouin spectroscopy system is low. In addition to being able to provide the frequency information of the spin wave in the frequency domain, the phase-resolved Brillouin spectroscopy system can also measure the phase information while retaining the spatial resolution, and can study the formation of coherent states in the magnon gas and the evolution of the eigenmodes of nonlinear spin waves, the change of the phase of linear and nonlinear spin waves with their propagation distance, that is, the uniqueness of the phase accumulation, the spin wave excitation process, and the two-dimensional phase structure of the spin wave beam in the magnetic anisotropic medium, etc., and is suitable for promotion and use in the laboratory. The phase-resolved Brillouin spectroscopy system provided by the present invention has a wide range of applications and can be applied to the study of other quasiparticles (such as acoustic phonons, etc.).

[0057] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0058] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A phase-resolved Brillouin spectroscopy system, characterized in that: include: A microwave pulse signal generating device (10) configured to generate a first microwave pulse signal and a second microwave pulse signal; A quasiparticle excitation device (20) is configured to carry a sample and absorb the first microwave pulse signal to excite quasiparticles locally in the sample; A laser light source (30) is configured to generate laser light so that the laser light is focused on a target position of the sample to generate Brillouin scattering with the quasiparticles to generate Brillouin scattered light; wherein the target position is adjustable; An electro-optic modulator (40) is configured to modulate the phase of the laser to generate frequency-shifted reference light under the drive of the second microwave pulse signal, wherein the frequency-shifted reference light interferes with the Brillouin scattered light; Wherein, the phase-resolved Brillouin spectroscopy is measured by adjusting the target position.

2. The system according to claim 1, characterized in that The microwave pulse signal generating device (10) comprises: A pulse generator (11) configured to generate a pulse signal; A microwave source (12) is configured to generate a continuous microwave signal and convert the continuous microwave signal into an initial microwave pulse signal under the action of the received pulse signal; The power beam splitter (13) is configured to split the initial microwave pulse signal into two paths to obtain the first microwave pulse signal and the second microwave pulse signal.

3. The system according to claim 2, characterized in that The microwave pulse signal generating device (10) further comprises: The attenuator (14) is configured to adjust the intensity of the second microwave pulse signal.

4. The system according to claim 2 or 3, characterized in that: The microwave pulse signal generating device (10) further comprises: The phase shifter (15) is configured to adjust the phase of the second microwave pulse signal.

5. The system according to claim 1, characterized in that The system further comprises: The beam splitter (50) is configured to reflect the laser light and the frequency-shifted reference light, and to transmit the frequency-shifted reference light and the Brillouin scattered light.

6. The system according to claim 1, characterized in that The system further comprises: A polarizer (60) is configured to adjust the relative intensities of the frequency-shifted reference light and the Brillouin scattered light to optimize the interference between the frequency-shifted reference light and the Brillouin scattered light.

7. The system according to claim 1 or 6, characterized in that: The system further comprises: The Fabry-Perot interferometer (70) is configured to analyze the interference result of the frequency-shifted reference light and the Brillouin scattered light, and output an interference signal of a preset frequency.

8. The system according to claim 1, characterized in that The frequency-shifted reference light and the Brillouin scattered light have the same frequency.

9. The system according to claim 1, characterized in that The quasiparticles include acoustic phonons or magnons; In the case where the quasiparticle is a magnon, the sample is a magnetic material, and the quasiparticle excitation device (20) is a resonant cavity.

10. The system according to claim 9, characterized in that In the case where the quasiparticle is a magnon, the system further comprises: The magnetic field generating device is configured to apply a magnetic field to the magnetic material on the surface of the resonant cavity.

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