Coherent control in quantum dot gain media using shaped pulses: a numerical study

Abstract

We present a numerical study of coherent control in a room temperature InAs/InP quantum dot (QD) semiconductor optical amplifier (SOA) using shaped ultra-short pulses. Both the gain and absorption regimes were analyzed for pulses with central wavelengths lying on either side of the inhomogeneously broadened gain spectrum. The numerical experiments predict that in the gain regime the coherent interactions between a QD SOA and a pulse can be controlled by incorporating a quadratic spectral phase (QSP) in the pulse profile. The sequential interaction with the gain medium of different spectral components of the pulse results in either suppression or enhancement of the coherent signatures on the pulse profile depending upon their proximity to the gain spectrum peak. In the absorption regime, positive QSP induces a negative chirp that adds up to that of a two photon absorption induced Kerr-like effect resulting in pulse compression while negative QSP enhances dispersive broadening of the pulse.

Coherent control in room-temperature quantum dot semiconductor optical amplifiers using shaped pulses

“…Due to the complexity of the SOA dynamics, we chose to demonstrate here the simplest experiment examining the effect of a quadratic SP (QSP) profile that spreads the pulse spectral components linearly in time. It confirms a recent numerical prediction [19] showing that this linear chirp has a major effect on the Rabi-oscillations triggered by such pulses; when the pulse is spectrally located on the short wavelength slope of the SOA gain curve, a positive linear chirp results in pronounced Rabi-oscillations, while a negative linear chirp diminishes them.…”

“…The interaction parameters and pulse intensities at the input are therefore modified artificially to the level that ensures a match of the calculated output pulse shapes with the shape of the measured ones and their evolutions. Most of the parameter values used here are presented in our previous publications concerning this model [15,19]. Here, the parameters that yield the best reproductions are: a group-velocity dispersion of 30000 fs 2 /mm, a two-photon absorption (TPA) coefficient of 30 cm/GW and an alpha parameter [23] of -0.6 representing the Kerr effect that accompanies TPA [15,23].…”

“…As shown, the pulses are resonant with the short wavelength slope of the gain spectrum. General modelling of the experiments at hand, discussed in [19], predicts that this spectral configuration plays a major role in the control of the coherent Rabi oscillations.…”

Carrier dynamics in a tunneling injection quantum dot semiconductor optical amplifier

“…The theoretical investigation of ultra-short pulses propagation in a QD amplifier is based on a semiclassical description of the light-matter interaction [18], solved in the dipole moment approximation. We employ a numerical finite-difference time-domain model, developed in [16,19,20], that solves Lindblad equations for the occupation probabilities of a cascade of two-level quantum systems having different transition energies, that represent the inhomogeneously broadened ensemble of QDs. Simultaneously, it solves Maxwells equation for the electromagnetic field of the propagating pulse, where the vector polarization includes contributions from the interaction with the QDs, from two-photon absorption (TPA) and its accompanying Kerr-like effect as well as from group velocity dispersion (GVD) and the refractive index dependence on the carrier population, known as the plasma effect [20].…”

Ultra-fast charge carrier dynamics across the spectrum of an optical gain media based on InAs/AlGaInAs/InP quantum dots

“…23 Details of the model formalism are given in Ref. 26. Here we introduce a modification in which the rate equations for the electron and the hole reservoirs, equations (1) and (2) in Ref.…”