EFFICIENCY OF SUBMILLIMETER-WAVE GENERATION AND AMPLIFICATION BY COHERENT WAVE-PACKET OSCILLATIONS IN SEMICONDUCTOR STRUCTURES

We discuss the emission of submillimeter waves from optically excited coherent wave-packet oscillations in quantum-well structures in terms of the emitted power. The material dynamics are treated in a two-band real-space density-matrix approach; the radiation process, by conventi onal antenna theory. Excitation geometries that assist cooperative rad iation from all points of the excited spot are proposed. We consider a mplification by phase-locked feedback of the terahertz wave to the emi tter in a resonator. Our results lead to concepts for optimized power extraction from coherent terahertz sources.