Mid-infrared laser heterodyne radiometer (LHR) based on a 3.53 μm room-temperature interband cascade laser

The performance of an interband cascade laser based laser heterodyne radiometer (LHR) is demonstrated in ground-based solar occultation mode. High-resolution (0.0033 cm^-1) transmission spectra near 3.53 μm were obtained for simultaneous atmospheric observations of H₂O and CH₄. Combined with the preprocessed measurement data (acquired at Hefei, China, on June 21th 2016), an optimal estimation method based retrieval algorithm is developed for data retrieval and error analysis. By considering the corrected atmospheric parameters, vertical profiles of H₂O and CH₄ are retrieved. Finally, the measured total column abundance and XCH4 were calculated to be 1.87 ± 0.02 ppm and 1.88 ± 0.02 ppm, respectively. The interband cascade laser-based laser heterodyne radiometer that is demonstrated in this manuscript has high potential for use in the development of compact, robust, and unattended LHR for spacecraft, airborne or ground-based atmospheric sensing.