Resonance Fluorescence from a Single Quantum Dot in a Nanopost Optical Cavity

Abstract

Scaling-up photonic quantum technologies will require the parallel operation of on-demand sources of identical single photons. In this context, broadband photonic structures embedding a single quantum dot (QD) are particularly appealing, as optimal source performance can be maintained upon QD spectral tuning. The nanopost─a nanocavity built with a segment of photonic wire─offers a broadband Purcell effect and a directive output beam. So far, however, QD-nanopost devices were only characterized using nonresonant optical excitation. Here, we employ a continuous wave laser to resonantly drive a single QD in a nanopost and detect its resonance fluorescence. Even though the nanopost introduces a significant optical roughness at the scale of the focused laser spot, a cross-polarization scheme leads to an excellent rejection of the excitation laser. We extensively characterize the QD optical emission by combining linescans and intensity correlation measurements, which are jointly analyzed with an analytical model. The emission features a pronounced antibunching (g⁽²⁾(0) = 0.02), close to the one of an ideal two-level system. For small driving powers, the homogeneous (total) spectral linewidth is a factor of 1.4 (5) above the Fourier limit. Combined with future device improvements, these results mark an important step toward the realization of bright and widely tunable sources of indistinguishable single photons.