Laser with radiation amplification by reflection from an inverted medium

A laser based on the amplification of light by reflection from an inverted medium was constructed. This made it possible to use a variety of active media differing in respect of the efficiency of utilization of the pump radiation and relatively insensitive to changes in temperature. The laser was a transparent waveguide resonator surrounded by an active medium with a refractive index smaller than that of the resonator material. Exciting radiation traveling in the resonator was reflected successively from the working surfaces at angles slightly smaller than the angle of total reflection of the boundary between the resonator and the active medium. In this way a thin layer of the medium was pumped and the radiation density in the layer was higher than that in the original beam.