Low-temperature tapered-fiber probing of diamond NV ensembles coupled to GaP microcavities

TL;DR

This paper introduces a low-temperature tapered-fiber technique to analyze diamond NV centers coupled to GaP microcavities, enabling high-contrast spectral measurements and decay rate analysis of the coupled emitters.

Contribution

It presents a novel platform combining tapered-fiber probing with NV centers and microcavities, allowing detailed performance testing of cavity-emitter systems at low temperatures.

Findings

Fiber-coupled Purcell factor is 2-3 times higher than free-space collection.

Ensemble averaging reduces the effective Purcell factor compared to a single emitter.

Method enables selective detection and spectral analysis of coupled emitters.

Abstract

In this work we present a platform for testing the device performance of a cavity-emitter system, using an ensemble of emitters and a tapered optical fiber. This method provides high-contrast spectra of the cavity modes, selective detection of emitters coupled to the cavity, and an estimate of the device performance in the single- emitter case. Using nitrogen-vacancy (NV) centers in diamond and a GaP optical microcavity, we are able to tune the cavity onto the NV resonance at 10 K, couple the cavity-coupled emission to a tapered fiber, and measure the fiber-coupled NV spontaneous emission decay. Theoretically we show that the fiber-coupled average Purcell factor is 2-3 times greater than that of free-space collection; although due to ensemble averaging it is still a factor of 3 less than the Purcell factor of a single, ideally placed center.