Autocollimation multibeam interferometer with spatial beam separation and its use in frequency selection of laser radiation

A new type of multibeam interferometer with side entrance of radiation is proposed. A theoretical analysis is made of a three-mirror autocollimation interferometer with side entrance, and it is shown both theoretically and experimentally that such an interferometer can be used as an efficient selector of longitudinal modes in laser resonators. Such a longitudinal-mode selector has advantages over a Fabry–Perot etalon in the resonators of high-power tunable lasers. In lasers of this type the use of an autocollimation multibeam interferometer with spatial beam separation ensures a considerable reduction in the optical loading on the components of the laser system and on coatings of mirrors in the selector, and it makes it possible to use the Fresnel reflection effectively.