We demonstrate theoretically the parametric oscillator behavior of a two-level quantum system with broken inversion symmetry exposed to a strong electromagnetic field. A multitude of resonance frequencies and additional harmonics in the scattered lig
ht spectrum as well as altered Rabi frequency are predicted to be inherent to such systems. In particular, dipole radiation at the Rabi frequency appears to be possible. Since the Rabi frequency is controlled by the strength of coupling electromagnetic field, the effect can serve for the frequency-tuned parametric amplification and generation of electromagnetic waves. Manifestation of the effect is discussed for III-nitride quantum dots with strong build-in electric field breaking the inversion symmetry. Terahertz emission from arrays of such quantum dots is shown to be experimentally observable.
A charge carrier confined in a quasi-one-dimensional semiconductor helical nanostructure in the presence of an electric field normal to the axis of the helix is subjected to a periodic potential proportional to the strength of the field and the helix
radius. As a result, electronic properties of such nanohelices are similar to those of semiconductor superlattices with parameters controlled by the applied field. These properties include Bragg scattering of charge carriers by a periodic potential, which results in energy gap opening at the edge of the superlattice Brillouin zone. This provides an opportunity for creating a new class of tunable high-frequency devices based on semiconductor nanohelices.
