Single photons are fundamental elements for quantum information technologiessuch as quantum cryptography, quantum information storage and optical quantumcomputing. Colour centres in diamond have proven to be stable single photonsources and thus essential components for reliable and integrated quantuminformation technology. A key requirement for such applications is a largephoton flux and a high efficiency. Paying tribute to various attempts tomaximise the single photon flux we show that collection efficiencies of photonsfrom colour centres can be increased with a rather simple experimental setup.To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colourcentres on the flat surface of a ZrO2 solid immersion lens. We found stablesingle photon count rates of up to 853 kcts/s at saturation under continuouswave excitation while having excess to more than 100 defect centres with countrates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we foundcount rates up to 2.4 Mcts/s for time intervals of several ten seconds. Itseems to be a general feature that very high rates are accompanied by ablinking behaviour. The overall collection efficiency of our setup of up to4.2% is the highest yet reported for N-V defect centres in diamond. Underpulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused aclick on the detector adding to 221 kcts/s thus opening the way towards diamondbased on-demand single photon sources for quantum applications.
展开▼
