Stimulated SBS are amongst the most intense high-frequency sound

Stimulated scattering processes are
nonlinear (NL) interactions in which an incident wave is converted to a
frequency up or down shifted scattered wave. The difference in the photon
energy between the incident and scattered wave is supplied by or taken up by
the NL medium. Various types of scattering processes are possible, each involve
different types of internal excitation of the medium. Stimulated Brillouin
scattering (SBS) involves interactions with sound waves in solids, liquids, or
gases or ion-acoustic waves in plasma.

SBS is known to be a valuable probe of
acoustic phonons in gases, liquids and solids. The acoustic waves generated in
solids due to SBS are amongst the most intense high-frequency sound waves and
this may sometimes damage the materials. SBS has recently been receiving considerable
attention owing to its numerous applications in diverse areas ranging from
optical phase conjugation (OPC), real-time holography, and pulse compression to
laser induced fusion.

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Brillouin Scattering

scattering, named after Léon Brillouin, refers
to the interaction of light and material
waves within a medium. 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). 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. 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:

A.   Mass
oscillation (acoustic) modes (called phonons);

B. Charge displacement modes (in
dielectrics, called polarons);

C.   Magnetic
spin oscillation modes (in magnetic materials, called magnons).