Off-beam QEPAS sensor using an 11-μm DFB-QCL with an optimized acoustic resonator

An off-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor was designed for ethylene detection using a distributed-feedback quantum cascade laser (QCL) operating in the mid-infrared around 11 mu m. The acoustic microresonator configuration was experimentally optimized using an original open-cell photoacoustic setup with a MEMS microphone. Correction factors based on theoretical acoustic models were introduced in order to accurately describe the response of millimeter-sized acoustic resonators. The optimized QEPAS sensor exhibited a limit of detection of 60 ppb for 60 s integration, giving a NNEA of 4.8 x 10(-8) W.cm(-1).Hz(-0.5). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement