There is a major interest in monitoring the fate of the earth’s ozone layer. A heterodyne spectrometer for the remote sensing of the vertical, integrated stratospheric ozone number density profile has been developed. A local oscillator ~LO! based on the tunable single-sideband CO2 laser with an external modulator capable of providing a sideband tuning range of 68 to 18 GHz on either side of the laser carrier.
Peter K. Cheo,
"Simplified tunable single sideband CO2 laser spectrometer: absorption measurements of ozone," Optical Engineering 36(5), (1 May 1997). https://doi.org/10.1117/1.601378