HARMONIC-GENERATION ACCOMPANYING COLLECTIVE SPONTANEOUS EMISSION

We discuss the possibility of producing harmonics while the process of collective spontaneous emission (superradiance) takes place in a soli d. Self correlations of dipole radiators induced by the emitted field lead to a reduction of the emission time and consequently to an increa se of the intensity. Estimations of the superradiant energy flux show that, for crystalline densities of radiators, this flux may be compara ble with the atomic unit. This assures the highly nonlinear behavior n ecessary to observe a pulse of high harmonics during superradiant puls e. We apply the Floquet-Bloch expansion to analyze the features of har monic production in the framework of the two-level model. (C) 1997 Opt ical Society of America [S0740-3224(97)01512-9].