Generation of tunable mid-infrared picosecond pulses at 76 MHz

Abstract

We describe and characterize an experimental apparatus that generates tunable infrared light pulses from 3.4 to 7.0 μm by difference-frequency mixing in AgGaS2. The pulses are 2.16 ps in duration, have a frequency bandwidth of 6.6 cm−1, and are produced at a 76-MHz repetition rate. Because the apparatus is compatible with low signal lock-in modulation and signal-averaging techniques, the infrared probe pulses can be used to measure very small (<10−4) vibrational absorption changes on fast time scales. We demonstrate this sensitivity by using the source to perform linear vibrational spectroscopy of adsorbed CO on Cu[111].