Synthèse et mesure des fréquences optiques

Abstract

Saturated-absorption stabilized gas lasers provide, in the optical region, accepted secondary fre- quency and length standards. Frequency stability and reproducibility of these lasers are reviewed. Using a broadband nonlinear device as a mixer, frequency synthesis of different lasers extend the frequency mea- surement range from microwaves to the near infrared. Using two carbon dioxide lasers, we have been able to measure the He-Ne laser frequency at 88 THz (3.39 03BCm). The frequency measurement range may be increased using different CO2 isotopes. Several nonlinear devices are able to mix optical frequencies from the submillimetric to the infrared wavelength. We review their characteristics as detectors and mixers, and we point out the possibility to extend it to the visible range. The use of new devices, the cavity stabilized superconducting oscillator and the methyl alcohol laser, with very narrow linewidths, inserted in a new laser frequency synthesis chain, should permit measurements of the methane