Spectra of the field and current oscillations in superlattices exposed to terahertz laser radiation

Nonlinear oscillations of field and current excited by terahertz laser radi ation in semiconductor superlattices were studied, taking into account the fact that the self-consistent internal field is multifrequncy. Oscillatory nonlinear susceptibilities, as well as dissipative and parametric instabili ties in superlattices, lead to ambiguous and hysteresis dependences of the oscillation spectra on the external-field amplitude and frequency. The spec trum shape features are controlled by spontaneous generation of a static fi eld and parametric amplification of external-field harmonics and subharmoni cs. The conventional approximation of single-frequency internal field was s hown to be unsatisfactory, especially for superlattices with a high electro n density. (C) 2001 MAIK "Nauka/Interperiodica".