Ultrafast pulse phase shift in a charged quantum dot- micropillar system

TL;DR

This paper demonstrates that a negatively charged quantum dot in a micropillar cavity can induce a giant optical phase shift of resonant pulses, surpassing previous experimental Kerr rotation measurements, with potential applications in ultrafast spin-photon control.

Contribution

The study introduces a quantum master equations model that accounts for spin relaxation and decoherence, predicting large phase shifts in a realistic cavity system, advancing ultrafast quantum photonics.

Findings

Achieves a phase shift of approximately ±π/2 in a weak-coupling regime.

Predicts phase shifts significantly larger than experimentally observed Kerr rotations.

Shows polarization rotation depends on initial conditions and electric field dynamics.

Abstract

We employ a quantum master equations approach based on a vectorial Maxwell-pseudospin model to compute the quantum evolution of the spin populations and coherences in the fundamental singlet trion transition of a negatively charged quantum dot embedded in a micropillar cavity. Excitation of the system is achieved through an ultrashort, either circularly or linearly polarised resonant pulse. By implementing a realistic micropillar cavity geometry, we numerically demonstrate a giant optical phase shift ($\sim \pm \pi/2$) of a resonant circularly polarised pulse in the weak-coupling regime. The phase shift that we predict considerably exceeds the experimentally observed Kerr rotation angle $(\sim{6 ^{\circ}})$ under a continuous-wave, linearly polarised excitation. By contrast, we show that a linearly polarised pulse is rotated to a much lesser extent of a few degrees. Depending on the initial boundary conditions, this is due to either retardation or advancement in the amplitude build-up in time of the orthogonal electric field component. Unlike previous published work, the dominant spin relaxation and decoherence processes are fully accounted for in the system dynamics. Our dynamical model can be used for optimisation of the optical polarisation rotation angle for realisation of spin-photon entanglement and ultrafast polarisation switching on a chip.