An echo of an exciting light pulse in quantum wells

Abstract

It is shown that non-sinusoidal oscillations appear in transmitted, reflected and absorbed light fluxes when light pulses irradiate a semiconductor quantum well (QW) containing a large number of equidistant energy levels of electronic excitations. The oscillation amplitude is comparable to the flux values for short pulses with the duration $\gamma_l^{-1} \leq \hbar/\Delta E$. A damped echo of the exciting pulse appears in the time intervals $2\pi\hbar/\Delta E$ for very short light pulses $\gamma_l^{-1}\ll \hbar/\Delta E$. Symmetric and asymmetric pulses with a sharp front are considered. Our theory is applicable to narrow QW's in a quantizing magnetic field when the equidistant energy levels correspond to the electron-hole pairs with different Landau quantum numbers.