Spectral stability of cavity-enhanced single-photon emitters in silicon

TL;DR

This paper demonstrates that integrating silicon emitters into Fabry-Perot resonators significantly reduces spectral diffusion and enhances optical coherence, advancing silicon-based quantum photonic technologies.

Contribution

It shows that using Fabry-Perot resonators instead of nanophotonic ones reduces spectral diffusion and improves coherence times in silicon quantum emitters.

Findings

Fivefold reduction in spectral diffusion linewidth to 4.0 MHz

Tenfold increase in optical coherence time to 20 microseconds

Spectral instability mainly caused by laser-induced electric-field fluctuations

Abstract

The unrivaled maturity of its nanofabrication makes silicon a promising hardware platform for quantum information processing. To this end, efficient single-photon sources and spin-photon interfaces have been implemented by integrating color centers or erbium dopants into nanophotonic resonators. However, the optical emission frequencies in this approach are subject to temporal fluctuations on both long and short timescales, which hinders the development of quantum applications. Here, we investigate this limitation and demonstrate that it can be alleviated by integrating the emitters into Fabry-Perot instead of nanophotonic resonators. Their larger optical mode volume enables both increasing the distance to crystal surfaces and operating at a lower dopant concentration, which reduces implantation-induced crystal damage and interactions between emitters. As a result, we observe a fivefold reduction of the spectral diffusion linewidth down to 4.0(2) MHz. Calculations and experimental investigations of isotopically purified 28-Si crystals suggest that the remaining spectral instability is caused by laser-induced electric-field fluctuations. In direct comparison with a nanophotonic device, the instability is significantly reduced at the same intracavity power, enabling a tenfold increase of the optical coherence time up to 20(1) microseconds. These findings represent a key step towards spectrally stable spin-photon interfaces in silicon and their potential applications in quantum networking and distributed quantum information processing.