Dual-beam subpicosecond broadband infrared spectrometer

Abstract

A method for obtaining broadband multichannel IR spectra with subpicosecond time resolution is described. Spectrally broad IR pulses, produced by difference-frequency mixing of two visible pulses in LiIO3, are split to make signal and reference pulses. After sample absorption, the IR pulses are upconverted by a second LiIO3 crystal to produce visible pulses that are dispersed on a CCD detector to yield transient spectra with 100-cm−1 bandwidth and 4-cm−1 resolution. With this dual-beam technique, spectra with sensitivities of 0.001 ΔOD are obtained.