Systematic study of the influence of coherent phonon wave packets on the lasing properties of a quantum dot ensemble

Abstract

The role of phonons for exciton and biexciton generation in an optically driven quantum dot D E Reiter, T Kuhn, M Glässl et al.Probing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons F Hargart, K Roy-Choudhury, T John et al. AbstractCoherent phonons can greatly vary light-matter interaction in semiconductor nanostructures placed inside an optical resonator on a picosecond time scale. For an ensemble of quantum dots (QDs) as active laser medium, phonons are able to induce a large enhancement or attenuation of the emission intensity, as has been recently demonstrated. The physics of this coupled phonon-exciton-light system consists of various effects, which in the experiment typically cannot be clearly separated, in particular, due to the complicated sample structure a rather complex strain pulse impinges on the QD ensemble. Here we present a comprehensive theoretical study how the laser emission is affected by phonon pulses of various shapes as well as by ensembles with different spectral distributions of the QDs. This gives insight into the fundamental interaction dynamics of the coupled phonon-excitonlight system, while it allows us to clearly discriminate between two prominent effects: the adiabatic shifting of the ensemble and the shaking effect. This paves the way to a tailored laser emission controlled by phonons.

Control of quantum dot laser emission by coherent phonon wave packets

“…The reason is that this enhancement happens due to the shaking effect of the ensemble. This effect has a reduced influence, when the strain dynamics is slower [8], which is the case here. For the example in Fig.…”

“…The normalized laser intensity in Fig. 2(a) exhibits only minor variations, but we can see that, although the number of QDs in resonance with the cavity shrinks, the intensity slightly increases due to the shaking effect [8]. In the case of a negative detuning of Δ 0 = −15 meV in Fig.…”

“…The expansion of the metal within a few picoseconds launches coherent phonon wave packets towards the laser system. the strain that corresponds to the displacement of the phonon field [8]. We have also shown that the model is capable of simulating the most important features of the laser emission dynamics [7].…”

“…In the range of small detunings around Δ 0 = 0 the two areas intersect and we find both, attenuations and enhancements, during the dynamics. This happens due to the interplay between adiabatic shift and shaking effect [8]. We now start from Fig.…”

“…The full set of equations is derived in Ref. [8] based on the usual dipole, rotating wave, and slowly varying envelope approximations. Here, we model the spectral distribution of the QDs by a Gaussian of width Δ QD centered around ω 0 :…”