Saturation of a resonant phonon-band mode by far-infrared excitation.

Abstract

We have observed saturation of a resonant phonon-band mode in an oxygen-doped silicon crystal. By use of a tunable pulsed high-power far-infrared laser, we excited the mode monochromatically and found that the absorption decreased strongly with increasing laser pulse energy. We show that the excitation resulted in a nonthermal state that decayed most likely by a process of spectral diffusion of phonons, caused by scattering at low-lying states.