Stimulated Emission and Gain

Ming Lai, Jean‐Claude Diels

The physical nature of the backward-stimulated emission can be understood by considering the angular distribution of the total radiation from a set of atomic dipoles driven by an intense laser beam. From the classical point of view, the backward-stimulated emission is simply a reflection from the interface between a dielectric and a gain medium from the mismatch in the imaginary parts of their indices of refraction. For bulk gain structure, backward-stimulated emission is usually too weak to be noticed. However, in the case of a gain layer much thinner than a wavelength or a periodic thin gain structure with a spacing of λ/2, the backward-stimulated emission is enhanced and can be as large as the forward stimulated emission in terms of the amplitude of radiation field.1

Mathieu Hautefeuille, Juan A. Hernández-Cordero

Ida Maria Catalano, Aldo Cingolani, Michele Ferrara +2 more

Stimulated emission in HgI2 at 80 °K due to an exciton-electron collision cooperative process is reported. The line shape of the stimulated emission band depends on the excitation wavelength. High optical gain has been measured. These effects are observed both with one- and two-photon pumping.

Galina A. Nemova

Ming Lai, Jean‐Claude Diels

Conditions for enhanced backward-stimulated emission are formulated for a thin layer of gain medium. A comparison is made between the enhanced backward-stimulated emission and the reflection from a dielectric film. A type of nonreciprocal reflective structure using a gain layer and a dielectric film is described. Such a device can be used to construct ring lasers with controllable unidirectional operation.