Jul 11 2013
Brillouin scattering may be described as a phenomenon of inelastic scattering of light in a physical medium brought about by thermally excited acoustical phonons. Brillouin scattering is usually observed in solid medium. Brillouin scattering may be considered as a form of Braggs scattering. This phenomenon is named after Leon Brillouin.
The compression of the medium results in the change in the refractive index, which leads to scattering or reflection at the point where there is a change in refractive index. Brillouin scattering occurs due to the scattering of light from acoustic modes. This article looks into the working, experimental set up and applications for Brillouin scattering phenomenon.
Experimental Set Up
In order to measure Brillouin scattering, a Brillouin spectrometer is set up. The set up is similar to a Fabry-Perrot interferometer. A laser is used as a light source, the light passes through filters and beam directing assembly to reach the sample medium. The Brillouin shift due to the acoustic phonons of the medium is measured by the interferometer.
Working
Brillouin scattering is produced by the interaction between the electromagnetic waves and a density wave. Brillouin scattering is brought about by the elasto-optic scattering mechanism caused by the dynamic fluctuations in the strain field. These fluctuating optical inhomogenities cause inelastic scattering of light while it is transmitted through it.
Applications
Some of the applications where the Brillouin scattering phenomenon is used are given below:
- Acoustic optic modulators
- Measurement of strain in optical fibers
- Measurement of elastic properties
References