Dynamics of light-induced reflectivity switching in gallium films deposited on silica by pulsed laser ablation

We present what is to our knowledge the first experimental study of light-induced reflectivity changes at an alpha -Ga/Si interface irradiated by femtosecond and picosecond laser pulses. After exposure, the reflectivity can increase from R congruent to .0.55, which is typical for alpha -Ga, to R congruent to 0.8, which is close to that of liquid Ga. The initial step in the reflectivity change of 2-4 ps is resolved with 150-fs laser pulses. The light-induced reflectivity change relaxes during 100 ns-10 mus, depending strongly on the background temperature of the Ga mirror and the laser fluence. (C) 2001 Optical Society of America.