Single-photon sources with optical-fiber integration

02 May 2007

UK researchers have demonstrated a 'plug and play' single-photon source based on single-quantum dots with an integrated optical-fibre output.

Xiulai Xu and colleagues from Cambridge University, UK, and Hitachi Europe, Cambridge, UK, describe a stable single-photon source with optical-fiber integration from InGaAs quantum dots J. Phys.: Conf. Ser. 61 1271-1275.

An optical fiber was attached to the sample surface to measure single-dot photoluminescence, which avoids light coupling between the quantum dots and free space. The researchers coupled a HeNe laser into the optical fiber to excite the quantum dots, and collected the emitted photoluminescence with the same optical fiber.

To verify the emission of single photons, the researchers performed correlation measurements of the luminescence using a Hanbury Brown and Twiss set-up with a 50/50 beamsplitter and two single-photon-counting avalanche photodiodes. The second-order correlation function at zero time delay is less than 0.1, which clearly shows single-photon emission.

The devices are stable and reproducible for an arbitrarily long time, which is very promising for real implementations of quantum key distribution and linear optical quantum computation.