Photoinduced amplification of phonons localized in a two-dimensional electron gas

This paper discusses how phonons localized within a two-dimensional electron gas are affected by the presence a strong electromagnetic wave whose electric field vector lies in the plane of the two-dimensional electron gas. A dispersion relation for the phonons is derived under the assumption and the electromagnetic wave affects the phonon subsystem only via the two-dimensional electron gas. When the energy of an electromagnetic wave quantum is large compared to the electron energies, new regimes of electron-phonon interaction become possible (which are forbidden by conservation laws in the absence of the wave), including regimes in which the open-quotes attenuationclose quotes of the phonons is negative (photoinduced gain). 7 refs