Acoustically pumped stimulated emission in GaAs/AlGaAs quantum wells

We report on an extremely narrow linewidth of a two-dimensional electron-gas photoluminescence in GaAs/AlGaAs quantum wells pumped by ultrasonic vibrations. Below the threshold pumping amplitude, the observed emission line is weak, broad, and undergoes a redshift consistent with the evolution of an electron-hole plasma recombination in the oscillating piezoelectric fields accompanying the sample vibrations. Above the threshold, a narrow emission line arises, which sharpens up to ∼0.1-meV full width at half maximum, and gains intensity with increasing pumping amplitude. Weighing different alternatives, it is suggested that the data are best explained within the framework of stimulated emission originating from the acoustically pumped injection of enhanced electron and hole densities.