External short-cavity diode-laser for MIR difference-frequency generation

A compact mid-infrared (MIR) laser system is described applying two single mode diode-lasers as pump and signal sources to generate difference-frequency radiation in AgGaS2. A spectral tuning range of 71.5 cm(-1) between 4.9-5.1 mum with an output power of 100 nW and linewidth of 1.2 x 10(-2) CM-1 (3.6 GHz) for the DFG laser system is obtained by mode behavior improvement of the pump source using an external short-cavity. The performance of such an external short-cavity MIR-DFG laser spectrometer is demonstrated by recording the fundamental absorption spectra of carbon monoxide ((CO)-C-12-O-16) and nitric oxide ((NO)-N-14-O-16) in a 10 cm long cell in order to estimate line-broadening coefficients of CO and NO molecules, which are of general interest in combustion diagnostics.