Selection of longitudinal laser modes by a nontilted intracavity Fabry-Perot etalon

The use of a Fabry-Perot etalon in selection of longitudinal cavity modes w as investigated. It was found that a Fabry-Perot etalon may be used for suc h selection in cavities with a convex mirror without tilting the etalon rel ative to the cavity axis. This avoids a number of limitations associated wi th tilting of the etalon. The mechanism of discrimination between the modes and of residual losses introduced by the etalon was analysed theoretically . Mode selection by a nontilted Fabry-Perot was achieved for an argon laser , the cavity parameters were optimised, and a high efficiency of conversion to a single-frequency regime (more than 70% in terms of the multimode lasi ng power, which was a factor similar to 1.5 higher than for a tilted etalon ) was attained.