Selective reflection from a glass–gas interface at high angles of incidence of light

Resonance lines of rubidium and cesium and injection lasers were used in a study of selective reflection from an interface between a transparent dielectric and an absorbing gas as a function of the angle of incidence of radiation and of its polarization, and of the concentration of atoms in a cell. Selective reflection resonances were observed against zero background when radiation was incident on the cell at the Brewster angle. The conditions for observation of selective frustrated total internal reflection (FTIR) were determined analytically and experimentally. The maximum reflection coefficient obtained was 95 ± 2%, which was 10 times greater than the nonresonant reflection coefficient. The spectral width of the region where FTIR was observed ranged from 0.1 to 1.5 cm ^– 1, depending on the concentration of atoms and the angle of incidence. The FTIR eifect was used to construct a selective component which made it possible to ensure narrow-band cw operation of an injection laser with an external resonator. Other potential applications of the FTIR effect in quantum electronics were also considered.