A system for measuring a target gas via laser absorption spectroscopy in an open-air configuration, comprising a mid-infrared distributed feedback interband cascade laser (mid-IR DFB-ICL) having a wavelength selected to correspond with a spectral absorption line of the target gas and first electronic circuitry to control the laser temperature, current and modulation frequency. The mid-IR DFB-ICL is mounted to a heat sink. The system includes an optical component that projects a beam of the mid-IR DFB-ICL onto a distal backscattering directionally-reflective target and an optical receiver assembly that receives a fraction of the laser light that is backscattered from the directionally-reflective target and focuses the collected light onto an uncooled photodetector having a spectral bandwidth and optical configuration selected to optimize signal-to-noise response to received laser light. The optical receiver assembly comprises a primary mirror for receiving laser light backscattered from the directionally-reflective target and focusing the collected light onto the uncooled photodetector.