Dynamics of the energy relaxation in a parabolic quantum well laser

Abstract

We explore two parabolic quantum well (PQW) samples, with and without Bragg mirrors, in order to optimise the building blocks of a Bosonic Cascade Laser. The photoluminescence spectra of a PQW microcavity sample is compared against that of a conventional microcavity with embedded quantum wells (QWs) to demonstrate that the weak coupling lasing in a PQW sample can be achieved. The relaxation dynamics in a conventional QW microcavity and in the PQW microcavity was studied by a non-resonant pump-pump excitation method. Strong difference in the relaxation characteristics between the two samples was found. The semi-classical Boltzmann equations were adapted to reproduce the evolution of excitonic populations within the PQW as a function of the pump power and the output intensity evolution as a function of the pump-pump pulse delay. Fitting the PQW data confirms the anticipated cascade relaxation, paving the way for such a system to produce terahertz radiation.

Ge/SiGe parabolic quantum wells

“…Polarization independent integrated optical switches based on QCSE have also been demonstrated by exploiting PQWs [12,13]. PQWs also find applications in light emitting devices: THz radiation has been detected from subband recombination in AlGaAs PQWs [14], and the nature of the subband states in the PQW has been considered for the fabrication of lasers, exploiting bosonic condensation of excitons [15][16][17].…”

Realization of Harmonic Oscillator Arrays with Graded Semiconductor Quantum Wells

“…Most studies of PQWs took place at the end of the 1980s, focusing on their structural analysis [13] or on 2D electronic gases for transport applications [14][15][16][17]. More recently, the interband optical properties have been studied in undoped structures [18]. However, the majority of these works only approximated the parabolic potentials via digital alloys.…”

Optically induced transparency in bosonic cascade lasers

“…A variety of theoretical considerations of bosonic cascades have since been considered, including the quantum statistics of the cascade levels [8] and the interplay of double bosonic stimulation coming from a THz cavity and the bosonic particles themselves [9]. Physical implementations of bosonic cascades can be based on excitons or exciton-polaritons in parabolic traps [10] and are presently under experimental development [11,12].…”