Special features of the distributed feedback lasers based on gyrotropic cubic crystals

The oscillation conditions were determined for the distributed feedback lasers based on gyrotropic cubic crystals. The frequencies of clockwise (counterclockwise) polarized longitudinal eigenmodes decrease (increase) by ω_ρ=ρc/n (ρ is the specific optical rotation of the crystal, n is the index of refraction, c is the speed of light in vacuum) relative to the Bragg frequency ω₀=πc/Λn (Λ is the phase grating period). The gain threshold is higher for the clockwise than for the counterclockwise polarized waves.