Theoretical analysis of spectral gain in a terahertz quantum-cascade laser: Prospects for gain at 1 THz

Abstract

In a recent Letter [Appl. Phys. Lett. 82, 1015(2003], Williams et al. reported the development of a terahertz quantum cascade laser operating at 3.4 THz or 14.2 meV. We have calculated and analyzed the gain spectra of the quantum cascade structure described in their work, and in addition to gain at the reported lasing energy of ≃ 14 meV, we have discovered substantial gain at a much lower energy of around 5 meV or just over 1 THz. This suggests an avenue for the development of a terahertz laser at this lower energy, or of a two-color terahertz laser.

THz and sub‐THz quantum cascade lasers

“…In this model the two levels considered are the ground state of the injector and the upper lasing state. More refined models for transport and gain calculations make use of nonequilibrium Green's functions [18], density matrices extended to extraction states too [19] and hybrid aproaches which include Monte Carlo [12] and coherence effects [20]. Using the same symbols as in Ref [17] the current density in the structure as a function of the applied electric field E can be written as:…”

Influence of doping density on electron dynamics in GaAs∕AlGaAs quantum cascade lasers

“…Together with experimental investigations, a systematic and compact theoretical modeling is a necessary step towards improvements of the existing structures and the understanding of physical processes within. These include Monte Carlo simulation, 34-37 nonequilibrium Green's function formalism, 38,39 as well as self-consistent rate equations model. 40,41 The doping level in the active region is an important parameter with particular influence on the dynamic working range of QCLs.…”

Metal-free quantum-based metamaterial for surface plasmon polariton guiding with amplification

“…The accuracy of this statement depends on k-dependence of effective mass model Amplification via intersubband transitions may be achived by different schemes, as it was shown both theoretically and experementaly [26 -33]. The most promissing technique is Quantum Cascade (QC) [26][27][28][29][30].…”