Difference-frequency generation of intense femtosecond pulses in the mid-IR (4-12 mu m) using HgGa2S4 and AgGaS2

Abstract

We compare the properties and the performance of HgGa2S4 and AgGaS2 in a high-power difference-frequency generation scheme mixing the signal and idler from a travelling wave optical parametric generator at 1 kHz. Femtosecond pulses from 3.7 to 12 mum with quantum efficiency of 40-80% are generated with HgGa2S4 which is about 1.2 times higher than with AgGaS2 typically used in that wavelength range. The maximum single pulse energy obtained exceeds 9 muJ near 4 mum and 1 muJ in the whole tunability range which represents about an order of magnitude improvement in comparison with previous results. The mid-infrared pulses are almost bandwidth limited with durations of the order of 200 fs and less (minimum 165 fs). (C) 2000 Elsevier Science B.V. All rights reserved