Brillouin scattering

Definition

From a quantum point of view, Brillouin scattering is an interaction of light magnons), or with other low frequency quasiparticles interacting with light. The interaction consists of an inelastic scattering process in which a phonon or magnon is either created (spectrometer based on a Fabry-Pérot interferometer.

Relationship to Raman scattering

The inelastic scattering process of Brillouin light scattering is in principle the same as Raman scattering. Historically Brillouin scattering denominates the scattering of acoustic phonons, while Raman scattering refers to the scattering from molecule vibrations and optic phonons. Nowadays the difference between Brillouin scattering and Raman scattering is considered to lie in the different experimental techniques and the resulting different available frequency range. The term Brillouin scattering labels an experimental detection of the frequency shift with an interferometer, while Raman scattering labels a setup employing a grating spectrometer. Brillouin scattering is technically limited to the detection of quasiparticles with frequencies below about 500 GHz, while with Raman scattering much higher frequencies in the THz range can be measured.

Stimulated Brillouin scattering

For intense beams (e.g. 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.

Discovery

The phenomenon of inelastic scattering of light due to acoustic phonons was first described by Leon Brillouin (1889-1969) in 1922 and 4 years later in 1926 independently by Leonid Mandelstam. In order to credit Mandelstam it is also denoted as 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.

Notes

See also

• scattering
• Raman scattering

References

• 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)