Nonlinear refraction in semiconductor lasers (review)

A strong optical nonlinearity is typical of semiconductors. A large contribution to the nonlinearity comes from the influence of free carriers on the refractive index and the carrier density itself depends on the intensity either because of photoelectric absorption or because of stimulated emission. In semiconductor lasers this gives rise to a number of effects, such as self-focusing, nonlinearity of the optical losses with associated emission dynamics anomalies, bistable operation in compound resonators and amplifiers, frequency self-modulation, and nonlinear scattering by electron density waves. Self-stabilization of single-frequency emission, which makes it possible to increase the intensity of coherent radiation emitted from a semiconductor laser, has the same physical basis as the aforementioned effects.