Abstract

Thin films of samarium sulfide (SmS) are known to undergo a phase transition from the metallic to the semiconducting state when irradiated by intense laser pulses. However, the dynamics of the phase transition in this intermediate-valence material are not well understood. We have measured changes in the reflection and transmission characteristics of SmS thin-film samples Irradiated by laser pulses ranging from 30 ps to 500 ns in duration. For pulses ⩾3 ns in duration, the SmS switches from the metallic to the semiconducting state during the laser pulse. The laser intensity required to induce the phase transition scales with pulse duration in a manner totally consistent with thermal diffusion through the thin (1000-A) SmS film and the transparent substrate. In contrast, the 30-ps pulses deposit energy in the sample on a time scale too short for thermal diffusion to dominate, and the laser intensity required for switching no longer scales as it does for longer pulses. Time-resolved measurements obtained with the 30-ps pulses are presented.

© 1985 Optical Society of America