Midinfrared cw difference-frequency generation using a synchronous scanning technique for continuous tuning of the full spectral region from 4.7 to 6.5 μm

Abstract

We report in this article an experiment of laser-based continuous-wave (cw) midinfrared difference-frequency generation using a synchronous scanning technique for continuous tuning of the complete spectral region from 4.7 to 6.5 μm (1550 to 2200 cm−1). A wavelength-tuned, noncritically phase-matched AgGaS2 crystal was used as the nonlinear optical mixing medium. Midinfrared output power of ∼10 μW was obtained by mixing two tunable lasers with ∼430 mW total pump power. The pump lasers were synchronously scanned during infrared wavelength tuning. The infrared frequency was deduced from the difference between the two laser frequencies which were simultaneously measured by wavemeters with an absolute accuracy of better than 0.007 cm−1. No reference cell was needed for frequency calibration. High-resolution spectra of carbonyl sulfide (OCS) were recorded for an evaluation of the frequency calibration and high-resolution spectroscopic characteristics.