Brillouin scattering 布里渊散射

In electromagnetism, Brillouin scattering (also known as Brillouin light scattering or BLS), named after Léon Brillouin, refers to the interaction of light with the material waves in a medium (e.g. electrostriction and magnetostriction). It is mediated by the refractive index dependence on the material properties of the medium; as described in optics, the index of refraction of a transparent material changes under deformation (compression-distension or shear-skewing).
在电磁学中，布里渊散射（也称为布里渊光散射或 BLS），以莱昂·布里渊命名，指的是光与介质中的物质波的相互作用（例如电致伸缩和磁致伸缩）。它是通过介质的材料特性对折射率的依赖来介导的；如在光学中描述的那样，透明材料的折射率在变形（压缩-拉伸或剪切-扭曲）下会发生变化。

The result of the interaction between the light-wave and the carrier-deformation wave is that a fraction of the transmitted light-wave changes its momentum (thus its frequency and energy) in preferential directions, as if by diffraction caused by an oscillating 3-dimensional diffraction grating.
光波与载流子变形波相互作用的结果是，部分传输光波改变其动量（因此其频率和能量）的方向，就像是由振动的三维衍射光栅引起的衍射一样。

If the medium is a solid crystal, a macromolecular chain condensate or a viscous liquid or gas, then the low frequency atomic-chain-deformation waves within the transmitting medium (not the transmitted electro-magnetic wave) in the carrier (represented as a quasiparticle) could be for example:
如果介质是固体晶体、大分子链凝聚物或粘稠液体或气体，则传输介质内的低频原子链变形波（而非传输的电磁波）在载体中（表示为准粒子）可能是：

1. mass oscillation (acoustic) modes (called phonons);
   质量振荡（声学）模式（称为声子）;
2. charge displacement modes (in dielectrics, called polarons);
   电荷位移模式（在介质中称为极化子）;
3. magnetic spin oscillation modes (in magnetic materials, called magnons).
   磁自旋振荡模式（在磁性材料中称为磁子）。

Mechanism 机制[edit]

From the perspective of solid state physics, Brillouin scattering is an interaction between an electromagnetic wave and one of the three above-mentioned crystalline lattice waves (e.g. electrostriction and magnetostriction). The scattering is inelastic i.e. the photon may lose energy (Stokes process) and in the process create one of the three quasiparticle types (phonon, polariton, magnon) or it may gain energy (anti-Stokes process) by absorbing one of those quasiparticle types. Such a shift in photon energy, corresponding to a Brillouin shift in frequency, is equal to the energy of the released or absorbed quasiparticle. Thus, Brillouin scattering can be used to measure the energies, wavelengths and frequencies of various atomic chain oscillation types ('quasiparticles'). To measure a Brillouin shift a commonly employed device called the Brillouin spectrometer is used, the design of which is derived from a Fabry–Pérot interferometer. Alternatively, high-speed photodiodes, such as those recovered from inexpensive 25-gigabit Ethernet optical transceivers, may be used in combination with a software-defined radio or RF spectrum analyzer.^[1]
从固态物理学的角度来看，布里渊散射是电磁波与上述三种晶格波之一（例如电致伸缩和磁致伸缩）之间的相互作用。散射是非弹性的，即光子可能会失去能量（斯托克斯过程），并在过程中产生三种准粒子类型之一（声子、极化子、磁子），或者通过吸收其中一种准粒子类型而获得能量（反斯托克斯过程）。光子能量的这种变化，对应于频率中的布里渊频移，等于释放或吸收的准粒子的能量。因此，布里渊散射可用于测量各种原子链振动类型（“准粒子”）的能量、波长和频率。为了测量布里渊频移，通常使用一种称为布里渊光谱仪的设备，其设计源自法布里-珀罗干涉仪。或者，也可以结合高速光电二极管（例如从廉价的 25G 以太网光收发器中回收的那些）与软件定义无线电或射频频谱分析仪来使用。

Contrast with Rayleigh scattering
与瑞利散射相比[edit]

Rayleigh scattering, too, can be considered to be due to fluctuations in the density, composition and orientation of molecules within the transmitting medium, and hence of its refraction index, in small volumes of matter (particularly in gases or liquids). The difference is that Rayleigh scattering involves only the random and incoherent thermal fluctuations, in contrast with the correlated, periodic fluctuations (phonons) that cause Brillouin scattering. Moreover, Rayleigh scattering is elastic in that no energy is lost or gained.
瑞利散射也可以被认为是由于传输介质中分子的密度、组成和取向的波动，以及其折射率在物质的小体积中（尤其是在气体或液体中）的波动。不同之处在于，瑞利散射仅涉及随机和不相干的热波动，与导致布里渊散射的相关、周期性波动（声子）相反。此外，瑞利散射是弹性的，即没有能量的损失或增益。

Contrast with Raman scattering
与拉曼散射对比[edit]

Raman scattering is another phenomenon that involves inelastic scattering of light caused by the vibrational properties of matter. The detected range of frequency shifts and other effects are very different compared to Brillouin scattering. In Raman scattering, photons are scattered by the effect of vibrational and rotational transitions in the bonds between first-order neighboring atoms, while Brillouin scattering results from the scattering of photons caused by large scale, low-frequency phonons. The effects of the two phenomena provide very different information about the sample: Raman spectroscopy can be used to determine the transmitting medium's chemical composition and molecular structure, while Brillouin scattering can be used to measure the material's properties on a larger scale – such as its elastic behavior. The frequency shifts from Brillouin scattering, a technique known as Brillouin spectroscopy, are detected with an interferometer while Raman scattering uses either an interferometer or a dispersive (grating) spectrometer.
拉曼散射是另一种现象，涉及由物质的振动特性引起的光的非弹性散射。与布里渊散射相比，检测到的频率偏移范围和其他效应非常不同。在拉曼散射中，光子通过一阶相邻原子之间键的振动和旋转跃迁的效应而散射，而布里渊散射是由大尺度、低频声子引起的光子散射。这两种现象的效应提供了关于样品非常不同的信息：拉曼光谱学可用于确定传输介质的化学成分和分子结构，而布里渊散射可用于测量材料的更大尺度性质，如其弹性行为。布里渊散射的频率偏移，一种称为布里渊光谱学的技术，通过干涉仪检测，而拉曼散射则使用干涉仪或色散（光栅）光谱仪。

Stimulated Brillouin scattering
受激布里渊散射[edit]

For intense beams of light (e.g. laser) traveling in a medium or in a waveguide, such as an optical fiber, the variations in the electric field of the beam itself may induce acoustic vibrations in the medium via electrostriction or radiation pressure. The beam may display Brillouin scattering as a result of those vibrations, usually in the direction opposite the incoming beam, a phenomenon known as stimulated Brillouin scattering (SBS). For liquids and gases, the frequency shifts typically created are of the order of 1–10 GHz resulting in wavelength shifts of ~1–10 pm in the visible light. Stimulated Brillouin scattering is one effect by which optical phase conjugation can take place.
对于在介质或波导中传播的强光束（例如激光），例如光纤，光束本身的电场变化可能通过电致限或辐射压力在介质中引起声学振动。由于这些振动，光束可能显示出布里渊散射，通常在与入射光束相反的方向，这种现象被称为受激布里渊散射（SBS）。对于液体和气体，通常产生的频率偏移约为 1-10 GHz，导致可见光中的波长偏移约为 1-10 pm。受激布里渊散射是光学相位共轭可以发生的一种效应。

Discovery 发现[edit]

Inelastic scattering of light caused by acoustic phonons was first predicted by Léon Brillouin in 1914 ^[2] . Leonid Mandelstam is believed to have recognised the possibility of such scattering as early as 1918, but he published his idea only in 1926.^[3] In order to credit Mandelstam, the effect is also called Brillouin-Mandelstam scattering (BMS). Other commonly used names are Brillouin light scattering (BLS) and Brillouin-Mandelstam light scattering (BMLS).
光子被声子引起的非弹性散射最早由勒昂·布里渊在 1914 年预测。据信列昂尼德·曼德尔施塔姆早在 1918 年就认识到了这种散射的可能性，但他直到 1926 年才发表了自己的想法。为了表彰曼德尔施塔姆，这种效应也被称为布里渊-曼德尔施塔姆散射（BMS）。其他常用的名称有布里渊光散射（BLS）和布里渊-曼德尔施塔姆光散射（BMLS）。

The process of stimulated Brillouin scattering (SBS) was first observed by Chiao et al. in 1964. The optical phase conjugation aspect of the SBS process was discovered by Boris Yakovlevich Zeldovich et al. in 1972.
受激布里渊散射（SBS）过程最早由 Chiao 等人于 1964 年观察到。SBS 过程的光学相位共轭方面是由 Boris Yakovlevich Zeldovich 等人于 1972 年发现的。

Fiber optic sensing 光纤传感[edit]

Brillouin scattering can also be employed to sense mechanical strain and temperature in optical fibers.^[4]
布里渊散射也可以用来感知光纤中的机械应变和温度。 ^[4]

See also 另见[edit]

• Brillouin spectroscopy 布里渊光谱学
• Scattering 散射
• Raman scattering 拉曼散射
• Nonlinear optics 非线性光学

References 参考资料[edit]

Notes 笔记[edit]

Sources 来源[edit]

• Brillouin, Léon (1914). "Diffusion de la lumière par un corps transparent homogène". Comptes Rendus de l'Académie des Sciences (in French). 158: 1331–4. Retrieved 2022-09-28.
  布里渊，莱昂（1914 年）。“透明均匀体的光扩散”。《法国科学院学报》（法文）。158：1331–4。检索于 2022-09-28 。
• Brillouin, Léon (1922). "Diffusion de la lumière et des rayons X par un corps transparent homogène". Annales de Physique. 9 (17). EDP Sciences: 88–122. Bibcode:1922AnPh....9...88B. doi:10.1051/anphys/192209170088. ISSN 0003-4169.
  布里渊，莱昂（1922 年）。"透明均匀体对光和 X 射线的扩散"。《物理学年刊》。9（17）。EDP 科学：88-122。Bibcode：1922AnPh....9...88B。doi：10.1051/anphys/192209170088。ISSN 0003-4169。
• L.I. Mandelstam, Zh. Russ. Fiz-Khim., Ova. 58, 381 (1926).
  L.I. Mandelstam，Zh. Russ. Fiz-Khim.，Ova. 58，381（1926 年）。
• Chiao, R. Y.; Townes, C. H.; Stoicheff, B. P. (1964-05-25). "Stimulated Brillouin Scattering and Coherent Generation of Intense Hypersonic Waves". Physical Review Letters. 12 (21). American Physical Society (APS): 592–595. Bibcode:1964PhRvL..12..592C. doi:10.1103/physrevlett.12.592. ISSN 0031-9007.
  焦瑞元; 汤斯, C. H.; 斯托伊切夫, B. P. (1964-05-25). "受激布里渊散射和相干产生强超声波". 物理评论快报. 12 (21). 美国物理学会 (APS): 592–595. Bibcode: 1964PhRvL..12..592C. doi: 10.1103/physrevlett.12.592. ISSN 0031-9007.
• B.Ya. Zel’dovich, V.I.Popovichev, V.V.Ragulskii and F.S.Faisullov, "Connection between the wavefronts of the reflected and exciting light in stimulated Mandel’shtam Brillouin scattering," Sov. Phys. JETP, 15, 109 (1972)
  泽尔多维奇、波波维切夫、拉古尔斯基和费苏洛夫，《激发的曼德尔申布里渲散射中反射光和激发光波前之间的联系》，苏联物理学杂志，15，109（1972 年）

External links 外部链接[edit]

• CIMIT Center for Integration of Medicine and Innovative Technology
  CIMIT 医学与创新技术整合中心
• Brillouin scattering in the Encyclopedia of Laser Physics and Technology
  激光物理与技术百科全书中的布里渊散射
• Surface Brillouin Scattering, U. Hawaii
  表面布里渊散射，夏威夷大学
• List of labs performing Brillouin scattering measurements (source BS Lab in ICMM-CSIC)
  执行布里渊散射测量的实验室列表（来源于 ICMM-CSIC 的 BS 实验室）