TABLE OF CONTENTS J. Reintjes and M. Bashkansky
Optical Sciences Division
Naval Research Laboratory
Washington, DC
Raman and Brillouin scattering are inelastic scattering processes in which the wavelength of the scattered radiation is different from that of the incident light and a change in the internal energy of the scattering medium occurs. The main distinction between Raman and Brillouin scattering is the type of internal mode involved. Raman scattering involves nonpropagating collective modes in the material. Examples include electronic excitations and molecular vibrations and rotations in liquids and gases, electronic excitations and optical phonons in solids, and electron-plasma oscillations in plasmas. Brillouin scattering involves low-frequency propagating waves, for example acoustic waves in solids, liquids, and gases and ion-acoustic waves in plasmas. The two processes exhibit a range of similarities and differences in the properties of the scattering process as well as in the materials that are involved. General descriptions of Raman and Brillouin scattering are given in Refs. 1 8. Collections of papers on specific aspects of Raman and Brillouin scattering are contained in Refs. 9 11. Review articles are given in Refs. 12 and 13.
Raman scattering occurs in a wide variety of solids, liquids, gases, and plasmas. The most common form of Raman scattering is one in which the incident light, termed the pump, is scattered into light at a longer wavelength, termed the Stokes wave, with the energy difference between the incident and scattered photons being taken up in excitation of the appropriate mode of the material.
