Changes in the spectra of picosecond stimulated emission from GaAs accompanied by signs of electron-phonon interaction

A nonmonotonic variation in the width of the emission spectra $\delta\hbar\omega_s$ of GaAs as the energy of the pump photon $\hbar\omega_{ex}$ is varied is observed at a fixed energy of a picosecond pump pulse $W_{\mathrm{ex}}$ giving rise to intrinsic stimulated emission. In the case of this nonmonotonic variation, the largest width of the spectra has been found to be close to the parameter $\Delta$, which is determined by the energy of a longitudinal optical (LO) phonon and by the masses of an electron and a heavy hole. As the nonmonotonicity of the dependence $\delta\hbar\omega_s = f(\hbar\omega_{ex})$ becomes more pronounced, modulation of this dependence and the dependence of the spectrum amplitude on $\hbar\omega_{ex}$ are observed. The modulation features signs of relation to the electron-LO-phonon interaction. The observed evolution of the modulation is not inconsistent with published suggestions concerning the development and destruction of screening of the electron-LO-phonon interaction in the case of a dense electron-hole plasma. The level of radiation losses in the sample affects the modulation and nonmonotonicity.