Numerical optimization of single-mode fiber-coupled single-photon sources based on semiconductor quantum dots

Abstract

We perform extended numerical studies to maximize the overall photon coupling efficiency of fiber-coupled quantum dot single-photon sources emitting in the near-infrared and O-band and C-band. Using the finite element method, we optimize the photon extraction and fiber-coupling efficiency of quantum dot single-photon sources based on micromesas, microlenses, circular Bragg grating cavities and micropillars. The numerical simulations which consider the entire system consisting of the quantum dot source itself, the coupling lens, and the single-mode fiber, yield overall photon coupling efficiencies of up to 83%. Our work provides objectified comparability of different fiber-coupled single-photon sources and proposes optimized geometries for the realization of practical and highly efficient quantum dot single-photon sources.

Coherent light scattering from a telecom C-band quantum dot

“…An outstanding challenge hampering network integration of C-band quantum dots is further the improvement of the limited extraction efficiency. Recent proposals integrating QD sources into circular Bragg gratings or micropillars structures in the telecom C-band show that coupling efficiencies into single mode fibres up to around 80% are possible while at the same time also providing Purcell enhancement of factors 10-43 [38,39]. Seeing that under non-resonant excitation the investigated QD has a coherence time only about a factor three higher than the average in InAs/InP QDs [10], we expect that combining resonant excitation with appropriate photonic engineering will enable the majority of the QDs to perform at the Fourier level with high efficiency.…”

Single-Pixel Fluorescence Spectroscopy Using Near-Field Dispersion for Single-Photon Counting and Single-Shot Acquisition

“…Coupling efficiencies from single emitters above 80% appear feasible in highly optimized geometries. 20 In contrast, the coupling of diffuse isotropic fluorescence emission from extended surfaces is governed by optical throughput or etendue, Φ ∝ (MFD/2) 2 (NA) 2 , given as an invariant of the optical system by the collected solid angle and beam size, provided by the numerical aperture of the fiber (NA) and its mode field diameter (MFD). Thus, optical throughput is enhanced by orders of magnitude with the introduction of a multimode optical fiber (MMF) of increased mode area and NA.…”

“…Common implementations of TS-DFT rely on a single-mode optical fiber (SMF), preserving the high spatial coherence of single transversal laser modes. Coupling efficiencies from single emitters above 80% appear feasible in highly optimized geometries . In contrast, the coupling of diffuse isotropic fluorescence emission from extended surfaces is governed by optical throughput or étendue, Φ ∝ (MFD/2) 2 (NA) 2 , given as an invariant of the optical system by the collected solid angle and beam size, provided by the numerical aperture of the fiber (NA) and its mode field diameter (MFD).…”

High-Performance Single-Photon Sources at Telecom Wavelength Based on Broadband Hybrid Circular Bragg Gratings

“…Hybrid circular Bragg gratings (CBGs) have recently emerged as a promising alternative to those platforms thanks to the presence of a backside gold mirror, which eliminates the loss of photons into the substrate as well as the issue of a fragile free-standing membrane that affects the original suspended version. − The first experiments with hybrid CBGs showed the ability to provide a moderate Purcell enhancement of both the exciton and the biexciton transitions as well as high extraction efficiency in a wide range of wavelengths, , leading to count rates >10 MHz. , However, they focused on the spectral region between 780 and 880 nm, which prevents their integration with the standard optical fiber infrastructure due to strong attenuation (>1 dB/km) at those wavelengths. Despite the publication of various design studies − and the demonstration of a device operating in the O-band, similar results at telecom wavelength have not been achieved yet and the degree of reproducibility remains an open question.…”