Infrared frequency upconverter for high-sensitivity imaging of gas plumes

A remote methane detection system has been developed using a single-frequency tunable optical parametric oscillator at 3.4 mu m infrared wavelength. The infrared received light is converted by a frequency upconverter with a strong pump beam to near-infrared wavelength at 0.81 mu m and detected by a sensitive photomultiplier. The conversion efficiency of the upconverter was 40% for the backscatter signal from a topographic target, and the detector sensitivity was 11 times higher than that of the cooled InAs detector. By raster scanning the infrared beam, imaging was realized for the methane gas plume with an accuracy of 20 parts in 10(6) m at the range of similar to 2 m. (c) 2007 Optical Society of America.