Optimization of a midinfrared high-resolution difference-frequency laser spectrometer

Improved performance of a continuous-wave (cw) laser spectrometer for Doppler-limited infrared spectroscopy of molecules based on difference-frequency generation (DFG) in AgGaS2 has been achieved. The spectrometer was configured to generate continuous scans of up to 1 cm−1 from 1550 to 2100 cm−1. An absolute precision of ∼6 × 10−3 cm−1 with a resolution of better than 1.0 MHz (3.3 × 10−5 cm−1) was achieved. Infrared powers of ∼20 μW were obtained by employing 90° Type I phase matching in a 45-mm-long AgGaS2 crystal. The high-resolution characteristics of the DFG spectrometer were evaluated by using H2O and N2O spectra. Preliminary infrared kinetic spctroscopy results involving the detection of transient CO radicals from 193-nm acetone photodissociation are also reported.