Directional emission of a deterministically fabricated quantum dot - Bragg reflection multi-mode waveguide system

TL;DR

This study demonstrates controlled directional emission from quantum dots integrated into waveguides, combining experimental measurements and numerical simulations to optimize chiral light-matter coupling for quantum information applications.

Contribution

It introduces a deterministic fabrication method for quantum dot waveguides and provides detailed analysis of chiral coupling dependence on QD position.

Findings

Maximum emission directionality contrast of 0.93 achieved

Oscillatory dependence of directionality on QD position observed

Numerical simulations agree with experimental results

Abstract

We report on the experimental study and numerical analysis of chiral light-matter coupling in deterministically fabricated quantum dot (QD) waveguide structures. We apply in-situ electron beam lithography to deterministically integrate single InGaAs/GaAs QDs into GaAs-DBR waveguides to systematically explore the dependence of chiral coupling on the position of the QD inside the waveguide. By a series of micro-photoluminescence measurements, we determine the directionality contrast of emission into left and right traveling waveguide modes revealing a maximum of 0.93 for highly off-center QDs and an oscillatory dependence of this contrast on the QD position. In numerical simulations we obtain insight into chiral light-matter coupling by computing the light field emitted by a circularly polarized source and its overlap with multiple guided modes of the structure, which enables us to calculate directional $\beta$-factors for the quantum emitters. The calculated dependence of the directionality on the off-center QD position is in good agreement with the experimental data. It confirms the control of chiral effects in deterministically fabricated QD-waveguide systems with high potential for future non-reciprocal on-chip systems required for quantum information processing.