Design and operation of a compact, portable, room-temperature mid-infrared gas sensor is reported. The sensor is based on continuous-wave difference-frequency generation (DFG) in bulk periodically poled lithium niobate at 4.6 µm, pumped by a solitary GaAlAs diode laser at 865 nm and a diode-pumped monolithic ring Nd:YAG laser at 1064.5 nm. The instrument was used for detection of CO in air at atmospheric pressure with 1 ppb precision (parts in 109, by mole fraction) and 0.6% accuracy for a signal averaging time of 10 s. It employed a compact multipass absorption cell with a 18-m path length and a thermoelectrically cooled HgCdTe detector. Precision was limited by residual interference fringes arising from scattering in the multipass cell. This is the first demonstration of a portable high-precision gas sensor based on diode-pumped DFG at room temperature. The use of an external-cavity diode laser can provide a tuning range of 700 cm-1 and allow the detection of several trace gases, including N2O, CO2, SO2, H2CO, and CH4.
© 1997 Optical Society of America
Original Manuscript: January 24, 1997
Revised Manuscript: April 30, 1997
Published: October 20, 1997
Thomas Töpfer, Konstantin P. Petrov, Yasuharu Mine, Dieter Jundt, Robert F. Curl, and Frank K. Tittel, "Room-temperature mid-infrared laser sensor for trace gas detection," Appl. Opt. 36, 8042-8049 (1997)