Use of a multibeam phase interferometer for achieving singlefrequency emission from lasers

A description is given of a method for mode selection in a laser resonator. This method is based on establishing between two parts of a light beam a phase shift which is very strongly dependent on the frequency. This phase shift is produced by a multibeam Gires–Tournois reflecting interferometer. Various ways of utilizing this method are discussed. The results of numerical calculations are given for one variant in which multilayer nonabsorbing dielectric coatings are used. It is shown that in this case the selectivity factor of the reflected beam can be of the order of 10⁴ or higher. The possibility of constructing a "nonquadratic" selector is considered. The principle of operation (diffraction losses in the undesired modes) of the proposed method resembles the diffraction selector method suggested earlier but it is distinguished by a higher selectivity and a shorter length of the selector. The method may be useful for lasers with a wide gain profile and those exhibiting wavelength hopping.