Tim Schröder, Friedemann Gaedeke, Moritz J Banholzer, and Oliver Benson (2011)
Ultrabright and efficient single-photon generation based on nitrogen-vacancy centres in nanodiamonds on a solid immersion lens
New Journal of Physics, 13:055017.
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 maximize 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 (N-V) 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 access to more than 100 defect centres with count rates from 400 to 500 kcts/s. For a blinking defect centre, we found count rates up to 2.4 Mcts/s for time intervals of several tens of seconds. It seems to be a general feature that very high rates are accompanied by 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.