POLARIZATION OSCILLATIONS IN COUPLED QUANTUM-WELLS - A SCHEME FOR THE GENERATION OF SUBMILLIMETER ELECTROMAGNETIC-WAVES

In a specially-designed coupled quantum-well (QW) system it is possible to selectivity prepare an initial nonstationary electronic state by interband photoexcitation in one of the wells. Excited electrons will oscillate between the two wells giving rise to an oscillating electric dipole moment. In a stacked system of identical QW pairs these dipoles add up producing a tangible alternating voltage which can be used to modulate the incident radiation intensity. With a properly-designed positive feedback loop, connecting the coupled QW system and the light modulator, it is possible, therefore, to generate self-excitation of dipolar oscillations. This would provide a new method of generating submillimeter electromagnetic waves, accompanied by ultrashort optical pulses, periodic at terahertz frequencies.