A cavity-based optical antenna for color centers in diamond

TL;DR

This paper introduces a planar Fabry-Pérot cavity optical antenna using silver mirrors on diamond membranes, significantly enhancing photon collection from color centers and enabling scalable, stable quantum emitter integration.

Contribution

It presents a novel planar cavity design that improves photon extraction and coupling for diamond color centers, with experimental validation showing substantial enhancement and potential for scalable quantum technologies.

Findings

Six-fold increase in photon collection rate from SnV centers

Theoretical enhancement factor of 60 in photon rate

Stable, scalable, and cryogenically compatible design

Abstract

An efficient atom-photon-interface is a key requirement for the integration of solid-state emitters such as color centers in diamond into quantum technology applications. Just like other solid state emitters, however, their emission into free space is severely limited due to the high refractive index of the bulk host crystal. In this work, we present a planar optical antenna based on two silver mirrors coated on a thin single crystal diamond membrane, forming a planar Fabry-P\'erot cavity that improves the photon extraction from single tin vacancy (SnV) centers as well as their coupling to an excitation laser. Upon numerical optimization of the structure, we find theoretical enhancements in the collectible photon rate by a factor of 60 as compared to the bulk case. As a proof-of-principle demonstration, we fabricate single crystal diamond membranes with sub-$\mu$m thickness and create SnV centers by ion implantation. Employing off-resonant excitation, we show a 6-fold enhancement of the collectible photon rate, yielding up to half a million photons per second from a single SnV center. At the same time, we observe a significant reduction of the required excitation power in accordance with theory, demonstrating the functionality of the cavity as an optical antenna. Due to its planar design, the antenna simultaneously provides similar enhancements for a large number of emitters inside the membrane. Furthermore, the monolithic structure provides high mechanical stability and straightforwardly enables operation under cryogenic conditions as required in most spin-photon interface implementations.