Role of a high gain of the medium in superradiance generation and in observation of coherent effects in semiconductor lasers

A theoretical model of superradiant pulse generation in semiconductor laser structures is developed. It is shown that a high optical gain of the medium can overcome phase relaxation and results in a built-up superradiant state (macroscopic dipole) in an assembly of electron—hole pairs on a time scale much longer than the characteristic polarisation relaxation time T₂. A criterion of the superradiance generation is the condition αc_mT₂ > 1, where α is the gain coefficient and c_m is the speed of light in the medium. The theoretical model describes both qualitatively and quantitatively the author's own experimental results.