Brillouin scattering

Brillouin scattering

Brillouin scattering, named after Léon Brillouin, occurs when light in a medium (such as air, water or a crystal) interacts with time dependent optical density variations and changes its energy (frequency) and path. The density variations may be due to acoustic modes, such as phonons, magnetic modes, such as magnons, or temperature gradients. As described in classical physics, when the medium is compressed its index of refraction changes, and a fraction of the traveling light wave, interacting with the periodic refraction index variations, is deflected as in a three-dimensional diffraction grating. Since the sound wave, too, is travelling, light is also subjected to a Doppler shift, so its frequency changes.



Lattice wave.svg

From a quantum perspective, Brillouin scattering is an interaction between an electromagnetic wave and a density wave (photon-phonon scattering), magnetic spin wave (photon-magnon scattering), or other low frequency quasiparticle. The scattering is inelastic: the photon may lose energy to create a quasiparticle (Stokes process) or gain energy by destroying one (anti-Stokes process). This shift in photon frequency, known as the Brillouin shift, is equal to the energy of the interacting phonon or magnon and thus Brillouin scattering can be used to measure phonon or magnon energies. The Brillouin shift is commonly measured by the use of a Brillouin spectrometer, based on a Fabry–Pérot interferometer.

Relationship to Rayleigh scattering

Rayleigh scattering, too, can be considered to be due to fluctuation in the density, composition and orientation of molecules, and hence of refraction index, in small volumes of matter (particularly in gases or liquids). The difference is that Rayleigh scattering considers only random and incoherent thermal fluctuations, in contrast with the correlated, periodic fluctuations (phonons) of Brillouin scattering.

Relationship to Raman scattering

Raman scattering is another phenomenon involving inelastic scattering processes of light with vibrational properties of matter. The detected frequency shift range and type of information extracted from the sample, however, are very different. Brillouin scattering denominates the scattering of photons from low-frequency phonons, while for Raman scattering photons are scattered by interaction with vibrational and rotational transitions in single molecules. Therefore the two techniques provide very different information about the sample: Raman spectroscopy is used to determine the chemical composition and molecular structure, while Brillouin scattering measures properties on a larger scale – such as the elastic behaviour. Experimentally, the frequency shifts in Brillouin scattering are detected with an interferometer, while Raman setup can be based on either interferometer or dispersive (grating) spectrometer.

Stimulated Brillouin scattering

For intense beams (e.g. laser light) travelling in a medium such as an optical fiber, the variations in the electric field of the beam itself may produce acoustic vibrations in the medium via electrostriction. The beam may undergo Brillouin scattering from these vibrations, usually in opposite direction to the incoming beam, a phenomenon known as stimulated Brillouin scattering (SBS). For liquids and gases, typical frequency shifts are of the order of 1–10 GHz (wavelength shifts of ~1–10 pm for visible light). Stimulated Brillouin scattering is one effect by which optical phase conjugation can take place.


Inelastic scattering of light by acoustic phonons was first predicted by Léon Brillouin in 1922. Leonid Mandelstam is believed to have recognised the possibility of such scattering as early as 1918, but he published it only in 1926.[1] 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).

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 Zel’dovich et al. in 1972.

Fiber Optic Sensing

Brillouin scattering can also be employed to sense mechanical strain and temperature in optical fibers.[2]

See also


  1. ^ Feînberg, E.L.: The forefather, Uspekhi Fizicheskikh Nauk, Vol. 172, 2002 (Physics-Uspekhi, 45, 81 (2002) doi:10.1070/PU2002v045n01ABEH001126)
  2. ^ Measures, Raymond M. (2001). Structural Monitoring with Fiber Optic Technology. San Diego, California, USA: Academic Press. pp. Chapter 7. ISBN 0-12-487430-4. 
  • Léon Brillouin, Ann. Phys. (Paris) 17, 88 (1922).
  • L.I. Mandelstam, Zh. Russ. Fiz-Khim., Ova. 58, 381 (1926).
  • R.Y.Chiao, C.H.Townes and B.P.Stoicheff, “Stimulated Brillouin scattering and coherent generation of intense hypersonic waves,” Phys. Rev. Lett., 12, 592 (1964)
  • 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)

External links

Wikimedia Foundation. 2010.

См. также в других словарях:

  • Scattering — is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non uniformities in the medium through which they pass. In… …   Wikipedia

  • Brillouin — could refer to:* Marcel Brillouin (1854–1948), a French physicist * His son Léon Brillouin (1889–1969), also a physicist ** Things named after him: *** The Brillouin function, a function that describes the magnetization of an ideal paramagnet *** …   Wikipedia

  • Scattering theory — Top: the real part of a plane wave travelling upwards. Bottom: The real part of the field after inserting in the path of the plane wave a small transparent disk of index of refraction higher than the index of the surrounding medium. This object… …   Wikipedia

  • Scattering (optics) — Optical scattering deals with the scattering, absorption, and extinction of electromagnetic radiation by particles, molecules and surfaces. Both single scattering and multiple scattering (i.e. radiative transfer) are considered in this category.… …   Wikipedia

  • Léon Brillouin — Infobox Scientist name = Léon Brillouin box width = 300px |200px image width = 200px caption = Léon Nicolas Brillouin (1889–1969) birth date = August 7,1889 birth place = Sèvres, Seine et Oise, France death date = October 4, 1969 death place =… …   Wikipedia

  • Raman scattering — or the Raman effect (pronounced: IPA| [rə.mən] ) is the inelastic scattering of a photon. Discovered By Dr. C.V. Raman in liquids and by Grigory Landsberg and Leonid Mandelstam in crystals.When light is scattered from an atom or molecule, most… …   Wikipedia

  • Umklapp scattering — [ Figure 2.: k vectors exceeding the first Brillouin zone (red) do not carry more information than their counterparts (black) in the first Brillouin zone.] Umklapp scattering (also U process or Umklapp process) is an anharmonic phonon phonon (or… …   Wikipedia

  • Surface Enhanced Raman Scattering — Illustration von Rayleigh , Strokes und Anti Strokes Streuung Als Raman Streuung (auch Raman Effekt oder Smekal Raman Effekt) wird die inelastische Streuung von Licht an Atomen oder Molekülen bezeichnet. Sie ist nach Chandrasekhara Raman benannt …   Deutsch Wikipedia

  • Laboratoire Léon Brillouin — 48° 43′ 37″ N 2° 09′ 09″ E / 48.7268125, 2.1523762 Le Laboratoire Léon …   Wikipédia en Français

  • Transparency and translucency — Diaphanes redirects here. For the genus of firefly, see Diaphanes (beetle). Translucence redirects here. For other uses, see Translucence (disambiguation). Translucent redirects here. For the Japanese manga series, see Translucent (manga).… …   Wikipedia

Поделиться ссылкой на выделенное

Прямая ссылка:
Нажмите правой клавишей мыши и выберите «Копировать ссылку»