In-plane resonant excitation of quantum dots in a dual-mode photonic-crystal waveguide with high β-factor

Abstract

A high-quality quantum dot (QD) single-photon source is a key resource for quantum information processing. Exciting a QD emitter resonantly can greatly suppress decoherence processes and lead to highly indistinguishable single-photon generation. It has, however, remained a challenge to implement strict resonant excitation in a stable and scalable way, without compromising any of the key specs of the source (efficiency, purity, and indistinguishability). In this work, we propose a novel dual-mode photonic-crystal waveguide that realizes direct in-plane resonant excitation of the embedded QDs. The device relies on a two-mode waveguide design, which allows exploiting one mode for excitation of the QD and the other mode for collecting the emitted single photons with high efficiency. By proper engineering of the photonic bandstructure, we propose a design with single-photon collection efficiency of β > 0.95 together with a single-photon impurity of ϵ < 5 × 10−3 over a broad spectral and spatial range. The device has a compact footprint of ∼ 50 μ m 2 and would enable stable and scalable excitation of multiple emitters for multi-photon quantum applications.

Performance of the nanopost single-photon source: beyond the single-mode model

“…There are also several broadband designs which aim at controlling and suppressing the background emission, Γ B , hereby obtaining large β factors and thus high collection efficiency in a broad spectral range. These designs include the photonic nanowire 16,[25][26][27][28] and the photonic crystal waveguide [29][30][31][32][33][34] . Other broadband designs include the circular Bragg grating or "bullseye" cavity 20,[35][36][37][38][39][40][41] .…”