Abstract
Efficiently interfacing photonic with semiconductor qubits plays an important role in future quantum communication applications. In this paper, we model a photon to exciton interface based on an optically active gate-defined quantum dot (OAQD) embedded in a carefully designed photonic crystal cavity constraining its emission profile via the Purcell effect while maintaining a low enough quality factor to allow for electrical tuning of the emission wavelength. By matching the in-plane k-vector of a cavity mode and the reciprocal lattice constant of the photonic crystal, vertical emission is obtained. A back-reflection mirror located below the cavity and integrated as part of an already predefined process flow allows for not only the increasing of the light extraction efficiency but also the tailoring of the extracted beam profile to match that of a single mode fiber. We numerically show that a photon emitted by the OAQD can be coupled to the targeted free-space Gaussian beam with a probability above 50%, limited by electrode absorption. Further efficiency improvement up to 90% is possible by using indium tin oxide instead of gold as a gate material.
Highlights
Semiconductor quantum dots (QDs) have proven to be promising candidates for high-performance SPSs.7 increasing the light extraction efficiency from QDs represents a major challenge due to total internal reflection (TIR) caused by the high refractive index contrast between the semiconductor materials and free space
For QDs buried in flat gallium arsenide (GaAs) substrates, less than 2% of the generated photons are able to escape
Different approaches have been pursued to increase the efficiency of SPSs, increasing the probability of emitted photons coupling into a cavity mode or the fraction of photons escaping the cavity to a given radiating mode
Summary
Semiconductor quantum dots (QDs) have proven to be promising candidates for high-performance SPSs.7 increasing the light extraction efficiency from QDs represents a major challenge due to total internal reflection (TIR) caused by the high refractive index contrast between the semiconductor materials and free space. By positioning an OAQD at the center of an H4 cavity and adjusting the mirror position, we numerically obtain a total light extraction efficiency of 55.8%, as simulated with the finite difference time domain (FDTD) method, together with a high quality Gaussian shaped far field emission pattern (>95% overlap).
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