Phase transformations of an InSb surface induced by strong femtosecond laser pulses

Phase transformations of InSb(211) induced by 130-fs laser pulses at 800 nm have been time resolved in a wide range of laser fluences. The pump-probe technique has been used, where bath optical reflectivity and reflected second-harmonic generation (SHG) from the probe pulses are monitored as functions of probe versus pump pulse delay. The results are indicative of InSb undergoing a phase transition to a centrosymmetric state in a few hundred femtoseconds at sufficiently high laser fluences, similar to GaAs studied earlier. The initial ultrafast drop of the second-harmonic signal following excitation in the high-fluence regime occurs within the same time interval for both InSb and GaAs, suggesting that these changes are governed by electronic excitation effects. Subsequent studies of the InSb sample surface morphology and of the reflectivity imply the formation of an amorphous layer on the surface following laser-induced melting. It is argued that a metastable metallic phase does not appear on the surface of InSb under femtosecond laser excitation at room temperature.