Nonlinear transmission and reflection of ultrashort laser pulses by a thin semiconductor film under two-photon generation of biexcitons.

The transmission and reflection of an ultrashort laser pulse by a thin semiconductor film under the conditions of resonance excitation of biexcitons by two photons are theoretically investigated. The numerical solutions of the macroscopic equations are found for various values of the film thickness, the detuning from the two-photon resonance, the laser pulse duration, and the intensity. These equations have been obtained in the framework of the generalized bipolariton model. In this model a biexciton is formed from virtual excitons of four kinds and only some of them interact with the light. It is shown that the thin film substantially transforms the incident pulse. For specific conditions, high and narrow transmission and reflection peaks can appear, or even trains of such peaks. In some cases their height can considerably exceed the amplitude of the incident pulse. The results are compared with similar results obtained on the basis of other models.