Towards Wannier-Stark THz superlattice laser

Exceptional points in bichromatic Wannier–Stark systems

The resonance spectrum of a tilted periodic quantum system for a bichromatic periodic potential is investigated. For such a bichromatic Wannier–Stark system, exceptional points, degeneracies of the spectrum, can be localized in parameter space by means of an efficient method for computing resonances. Berry phases and Petermann factors are analysed. Finally, the influence of a nonlinearity of th...

Stark-wannier Ladders and Cubic Exponential Sums

Fractal stabilization of Wannier-Stark resonances

– The quasienergy spectrum of a Bloch electron affected by dc-ac fields is known to have a fractal structure as function of the so-called electric matching ratio, which is the ratio of the ac field frequency and the Bloch frequency. This paper studies a manifestation of the fractal nature of the spectrum in the system “atom in a standing laser wave”, which is a quantum optical realization of a ...

Broadband semiconductor superlattice detector for THz radiation

We report on a broadband GaAs/AlAs superlattice detector for THz radiation; a THz field reduces the current through a superlattice, which is carried by miniband electrons, due to modulation of the Bloch oscillations of the miniband electrons. We studied the detector response, by use of a free electron laser, in a large frequency range ~5–12 THz!. The responsivity showed strong minima at frequen...

Reflection of THz Radiation by a Superlattice

The dynamics of a charged particle in a superlattice under the action of an external electric field has been the subject of intense research [1–6]. Under different conditions, an electron is predicted to reveal a variety of time-dependent phenomena such as Bloch oscillations [1], Zener tunneling [2], self-induced transparency [3], miniband collapse [4], negative differential conductivity, and a...