GaSb /GaAs quantum rings as single photon sources

Quantum technologies exploit the exotic properties of nature described by quantum mechanics to deliver devices with unprecedented speed, accuracy or completely new functionalities, which simply do not exist at present. Quantum cryptography is one such technology: communication whose security is guaranteed by fundamental laws of quantum mechanics. The implementation of quantum cryptography relies on the ability to generate single photons of light on demand. Several different physical systems have been used to generate single photons, but very few of them are suitable for commercial production. An ideal single photon source (SPS) should be fast, cheap, operate at room temperature, and emit photons at the wavelengths used in existing optical-fibre telecoms networks. A practical SPS is expected to be very like a type of semiconductor laser diode called a vertical cavity surface emitting laser (VCSEL). We will assess the feasibility of mass-producing low-cost SPSs by developing novel VCSEL devices whose active regions incorporate semiconductor nanostructures called self-assembled quantum rings.