van Well, BenMurray, StuartHodgkinson, JanePride, Russ D.Strzoda, RainerGibson, GrahamPadgett, Miles2006-10-022006-10-022005-06van Well B, Murray S, Hodgkinson J, et al., (2005) An open-path, hand-held laser system for the detection of methane gas. Journal of Optics A: Pure and Applied Optics Volume 7, Issue 6, pp. S420-S4241464-4258http://hdl.handle.net/1826/1198http://dx.doi.org/10.1088/1464-4258/7/6/025We have developed an open-path hand-held gas detector incorporating a distributed feedback InGaAs laser diode at 1.65 µm. Incorporated into a hand-held transceiver unit, the emitted laser beam is backscattered from nearby surfaces, collected and focused onto an amplified InGaAs detector using a 150 mm diameter plastic Fresnel lens. At ranges of 4–5 m, a typical backscattered signal is tens of nanowatts of laser light. Applying second derivative wavelength modulation spectroscopy gives a sensitivity to methane of better than 10 parts per million over a one metre path length. A number of demonstration units have been fabricated and successfully evaluated by end users.742661 bytesapplication/pdfenmethanewavelength modulation spectroscopyinstrumentationinfrared spectroscopyremote detectionArticle