Loss and gain in Bloch oscillating super-superlattices: THz Stark ladder spectroscopy

Abstract

Bloch oscillation in electrically biased semiconductor superlattices offer broadband terahertz gain from DC up to the Bloch frequency or Stark splitting. Useful gain up to 2-3 terahertz can provide a basis for solid-state electronic oscillators operating at 10 times the frequency of existing devices.A major stumbling block is the inherent instability of the electrically biased doped superlattices to the formation of static or dynamic electric field domains. To circumvent this, we have fabricated super-superlattices in which a large superlattice is punctuated with heavily doped regions. The short superlattice sections have subcritical "nl" products Room temperature, terahertz photon assisted transport in short InGaAs/InAlAs superlattice cells allows us to determine the Stark ladder splitting as the superlattice is electrically biased and confirms the absence of electric field domains in short structures.Absorption of radiation from 1.5 to 2.5 THz by electrically biased InAs/AlSb super-superlattices exhibit a crossover from loss to gain as the Stark ladder is opened. Measurements are carried out at room temperature in a novel planar terahertz waveguide defined by photonic band gap sidewalls and loaded with an array of electrically biased super-superlattices. The frequency dependent crossover voltage indicates ~ 80% participation of the super-superlattice.

Theory of relaxation for spontaneous emission of Bloch oscillation radiation2S3 glass

“…(36) and (37) where the interface roughness model is explored, that is, the lattice comb of localized planar interface inhomogeneities with randomly distributed planar interface roughness defined by an ensemble averaged autocorrelation function (9) and (10). Clearly the results of evaluating Eqs.…”

“…Relevant to the subject of this paper is the coherent emission of electromagnetic radiation from Bloch oscillations in electrically biased semiconductor superlattices (SLs) [3][4][5][6][7][8][9][10][11][12]. In the case when the bias is chosen that the radiation output is in the terahertz regime, this allows for the possibility of inversionless terahertz lasers [13].…”