Abstract

Phonon dynamics in photoexcited Forsterite–a new tunable solid state laser–has been studied by time resolved spontaneous Raman scattering following absorption in ³T₂ electronic state. High rate of photoexcitation by 400 fs pulses are responsible for creation of nonequilibrium phonon population in the excited state. Phonons are generated by relaxation of the photoexcited electrons in the excited state. The finite relaxation time of phonons and strength of electron-phonon interactions produces the observed high nonequilibrium distribution during the short time after excitation. The short pulse measures the hot phonons while the longer pulses measure overall phonon population. These measurements give direct information on which nonradiative process and which phonons are involved in the relaxation of photoexcited ions in electronic state. For shortest pulse of 400 fs the 220-cm^–1 mode appears to be coupled with photoexcited tetravalent chromium Cr⁴⁺ showing the nonequilibrium distribution.

© 1990 Optical Society of America