Dual frequency selection in lasers using an anisotropically filled reflecting interferometer

A new intracavity high-resolution frequency-selective element is proposed in the form of a reflecting interferometer with a thin-film selector (absorbing film, diffraction structure), containing an anisotropic dielectric. This element is installed instead of the resonator mirror. The operating principle is based on the combined influence of absorption in the film and of the difference between the optical lengths of the interferometer for the ordinary and extraordinary waves. The analysis shows that the selectivity achieved is comparable with that obtained using two isotropic interference devices simultaneously. It is noted that the proposed element has an advantage in terms of selectivity over the traditionally used combination of a highresolution interferometer and a Lyot filter. The results are presented of an experimental investigation of a reflecting interferometer containing a birefringent quartz plate and operating at the $0,63\mu m$ wavelength.