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

Abstract

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 μm with an output power of 100 nW and linewidth of 1.2 × 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 (12C16O) and nitric oxide (14N16O) 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.