Controlling the intensity and fluctuations of light upon its selective reflection

Selective reflection of a semiconductor laser beam by a resonant gas is studied. The experiments were performed under conditions where the laser frequency is determined by the laser cavity mode structure. In this case, characteristic steps—intensity quasi-levels—arise on the reflectivity resonances. It is shown that the height of the quasi-levels depends on the degree of saturation of the resonance reflection by the laser field. Low-noise reflectivity regimes with different sensitivities to external signals are found on these quasi-levels.