Wide-bandgap nonlinear crystal LiGaS for femtosecond mid-infrared spectroscopy with chirped-pulse upconversion.

Femtosecond time-resolved mid-infrared (MIR) spectroscopy based on chirped-pulse upconversion is a promising method for observing molecular vibrational dynamics. A quantitative study on nonlinear media for upconversion is still essential for wide applications, particularly at the frequencies below 2000  cm. We evaluate wide-bandgap nonlinear crystals of Li-containing ternary chalcogenides based on their performance as the upconversion medium for femtosecond MIR spectroscopy.