Sub-Doppler Frequency Measurements on OCS at 87 Thz (3.4 um) with the CO OvertoneLaser: Considerations and Details

摘要

The authors have investigated two techniques for making sub-Doppler frequencymeasurements with the CO overtone laser. They studied three OCS transitions whose frequencies overlap either directly with CO (Delta)V=2 overtone transition frequencies or with the overtone lines after they have been shifted by an acousto-optic modulator. The authors have investigated both conventional saturated-absorption and an optical heterodyne polarization. While they eventually used the latter technique for their measurements, it is too cumbersome to use as a conventional laser stabilization tool. Saturation absorption is considerably simpler and has potential for a more accurate measurement, if some technical problems are overcome. This becomes more important in the light of a potential use of the CO (Delta)v=2P(sub 26)(9) transition in a new frequency chain. This transition was used for the OCS P(27) 10(sup 0)1-00(sup 0)0 measurement. Polarization spectroscopic techniques with optical heterodyne detection were used to observe the features and then to provide the discriminant for locking the overtone laser to the OCS transitions. A CO2 laser synthesizer was used for the frequency measurement basis.