Two-mode gas lasers and their applications in spectroscopy and optical frequency standards (review)

An analysis is made of the problems involved in operating and using two-mode low-power cw gas lasers in nonlinear laser spectroscopy and metrology. The high sensitivity to weak lines of the saturated dispersion makes two-mode nonlinear laser spectroscopy one of the most promising methods for the detection of optical resonances of up to 100 Hz wide and for the development of optical frequency standards having a reproducibility of 10−14–10−15.