Compact gas sensor using a pulsed difference-frequency laser spectrometer

We present a novel compact pulsed laser spectrometer based on difference-frequency mixing of a cw tunable external-cavity diode laser (795-825 nm) and a pulsed Nd:YAG laser (1064 nm) in bulk LiNbO(3) . The pulsed mid-IR source is continuously tunable from 3.16 to 3.67microm and exhibits a linewidth of only 154 MHz, a peak power of approximately 50microW , and a pulse duration of 6 ns at a 6.5-kHz repetition rate. Spectra of methane in room air and formaldehyde have been recorded at room-temperature operation in a multipass cell with deduced detection limits of 10 and 40 parts in 10(9) , respectively.