Population-inversion and gain estimates for a semiconductor TASER

Abstract

Abstract-We have investigated a solid-state design advanced (see Soref et al. in SPIE Proceedings, vol. 3795, p. 516 , 1999) to achieve a terahertz-amplification-by-the-stimulated-emission-of-radiation (TASER). The original design was based on lightto heavy-hole intersubband transitions in SiGe/Si heterostructures. This work adapts the design to electron intersubband transitions in the more readily available GaAs/Ga 1 Al As material system. It is found that the electric-field induced anti-crossings of the states, derived from the first excited state with the ground states of a superlattice in the Stark-ladder regime, offers the possibility of a population inversion and gain at room temperature.

Self-consistent scattering model of carrier dynamics in GaAs-AlGaAs terahertz quantum-cascade lasers

“…This has stimulated a number of experimental [9], [10] and theoretical [11] studies of QCL structures designed for emission at terahertz frequencies well below the forbidden phonon Reststrahlenband. Considerable research effort has recently resulted in theoretical prediction of population inversion by Monte Carlo studies [12], followed by luminescence measurements [13], and finally the laser action [14] at m (4.4 THz) in a GaAs-AlGaAs QCL.…”

“…The scattering time is a function of both and , the initial and final subband populations. Hence, this set of equations has to be solved selfconsistently using an iterative procedure [11], [19], [20].…”

Gain-maximized GaAs/AlGaAs quantum-cascade laser with digitally graded active region

“…The GaAs/AlGaAs system may also play a crucial role in lasing in the far-infrared range. [12][13][14][15][16][17][18] Generally, the main task in the design of a QCL is to maximize the gain, by designing a suitable potential profile with the desired energy spectrum and wave functions, which determine the transition dipole moment͑s͒ and transition rates, and eventually the gain. The charge transport in QCLs is mainly due to incoherent-scattering mechanisms, 19 and all principal scattering mechanisms, i.e., electron-longitudinal optical ͑LO͒ phonon and electron-electron, have to be included.…”

“…In order to extract the output characteristic of the DG QCL beyond the three-level approximation and compare it with the recently realized GaAs/Al 0.45 Ga 0.55 As TQW QCL, 10 we performed a full self-consistent rate equation modeling 16,29 of the electron scattering transport within the 15-level model of the QCL. 30 From the self-consistent solution, the population inversion ⌬n i ϭn 9 Ϫn 6 in the steady state was obtained, and the modal gain was calculated from 24…”

Dilute magnetic semiconductor quantum-well structures for magnetic field tunable far-infrared/terahertz absorption

“…The magnetic properties of DMS are determined by the strong exchange interaction between the and band electrons and the [5] electrons associated with the localized magnetic ions. This ex- change interaction affects processes which involve electrons in the conduction and valence bands, exciton and impurity levels and induces unique magneto-optical properties which are qualitatively different from those observed in nonmagnetic semiconductors [12], [13].…”