Basic Concepts of Inelastic Light Scattering, Experiments on Quantum Wells

Abstract

Inelastic light scattering – or Raman scattering – is the scattering of light by a medium, where in the scattering process excitations are created (Stokes process) or annihilated (Antistokes process) within the medium. In solids, these excitations can be various types of elementary excitations, like phonons, magnons, or – as considered in this book – electronic excitations. Historically, the scattering by optical phonons, or by internal vibrations of molecules, is called Raman scattering, and the scattering by acoustic phonons Brillouin scattering. For electronic Raman scattering, often the term inelastic light scattering is used, so in this book. Figure 4.1 shows schematically the Stokes and Antistokes processes, where a photon with energy ħω _I and momentum k _I is scattered by the creation or annihilation of an elementary excitation with energy ħω and momentum q. The scattered photon has an energy ħω _S and momentum k _s . This means, each scattered photon in the Stokes component is associated with a gain in energy ħω by the sample. Similarly, the sample loses energy ħω for each scattered photon in the Antistokes component