Ultra-bright and efficient single photon generation based on N-V centres in nanodiamonds on a solid immersion lens

TL;DR

This paper demonstrates a simple setup using nanodiamonds on a solid immersion lens to achieve ultra-bright, efficient single photon emission from N-V centers, with record collection efficiency and high count rates suitable for quantum technologies.

Contribution

It introduces a straightforward method to significantly enhance photon collection efficiency from N-V centers in nanodiamonds, reaching the highest reported values for such systems.

Findings

Stable single photon count rates up to 853 kcts/s at saturation.

Collection efficiency of up to 4.2%, the highest reported for N-V centers.

Count rates up to 2.4 Mcts/s for blinking defect centers.

Abstract

Single photons are fundamental elements for quantum information technologies such as quantum cryptography, quantum information storage and optical quantum computing. Colour centres in diamond have proven to be stable single photon sources and thus essential components for reliable and integrated quantum information technology. A key requirement for such applications is a large photon flux and a high efficiency. Paying tribute to various attempts to maximise the single photon flux we show that collection efficiencies of photons from colour centres can be increased with a rather simple experimental setup. To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colour centres on the flat surface of a ZrO2 solid immersion lens. We found stable single photon count rates of up to 853 kcts/s at saturation under continuous wave excitation while having excess to more than 100 defect centres with count rates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we found count rates up to 2.4 Mcts/s for time intervals of several ten seconds. It seems to be a general feature that very high rates are accompanied by a blinking behaviour. The overall collection efficiency of our setup of up to 4.2% is the highest yet reported for N-V defect centres in diamond. Under pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a click on the detector adding to 221 kcts/s thus opening the way towards diamond based on-demand single photon sources for quantum applications.