Long-wave IR chemical sensing based on difference frequency generation in orientation-patterned GaAs

The combination of continuous-wave difference frequency generation based on quasi-phase-matched (QPM) gallium arsenide with cavity ring-down spectroscopy is explored for use in spectroscopic and chemical sensing applications. The advent of QPM materials based on orientation-patterned GaAs (OP-GaAs) offers a significant advantage over traditional ferroelectric QPM materials of extended wavelength coverage into the spectroscopically important 8–12 μm region. In this work, the outputs from two tunable, external cavity diode lasers covering the 1.3 μm and 1.5 μm telecom bands were amplified then mixed in an orientation-patterned GaAs crystal, producing several microwatts of tunable radiation in the 7–9 μm region. We also evaluate the use of a low-power DFG source for use in cavity ring-down spectroscopy. PACS 82.80.Gk; 42.62.Fi; 42.70.Hj; 42.65.Ky