Electron-Population Bragg Grating Induced in an Al_xGa_{1 –x}As–GaAs–Al_xGa_{1 –x}As Heterostructure by Intrinsic Stimulated Picosecond Emission

Abstract

It is shown that modulation of the spectrum of stimulated picosecond emission generated in an Al_xGa_{1 – x}As–GaAs–Al_xGa_{1 – x}As waveguide heterostructure upon the optical pumping of GaAs, as well as a number of previous experimental results, can be explained under the assumption that the emission forms a symmetric modification of the Bragg grating of the nonequilibrium electron population in GaAs. The boundary conditions determining the grating design are proposed. To satisfy them, the grating can change only discretely. The latter is consistent with a change in the modulation of the spectrum of light absorption in GaAs, which reflects the emission-stimulated modulation of the population depletion. Inducing the grating, i.e., spatial hole burning, is one of the reasons for the multimode character of the emission, competition and switching of its modes, and modulation of the gain spectrum (frequency hole burning). The same is possible in a semiconductor laser, as in a waveguide.