Broadband thermal infrared heterodyne spectro-radiometry using an external cavity quantum cascade laser as a tunable local oscillator has been performed over a frequency range of more than 100 cm-1 at a central frequency of 1190 cm-1. Heterodyne spectro-radiometry is demonstrated for two local oscillator tuning modes: broadband tuning for transmission and emission spectroscopy of broadband absorbers (Freon 12), and broadband frequency selection in combination with fine continuous frequency tuning for high-resolution (0.021 cm-1) transmission spectroscopy (N 2O). In each case concentration retrievals are performed and analyzed. The spectro-radiometer noise level is demonstrated to be twenty two and eight times the fundamental shot-noise limit in the two scanning modes respectively.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics