CORDIS

Single-photon detection is an emerging technology, with applications ranging from medical imaging and LIDAR systems to space communication and fundamental quantum optics. Moreover, single-photon detectors are considered an enabling technology for the development of quantum information science, and the quantum computer.

Currently, single-photon detection is carried out using semiconductor-based avalanche photodiodes; however, this technology is limited by large timing jitter, unavoidable dark counts, afterpulsing, and limited detection efficiency. A recently proposed alternative relies on a superconducting nanowire biased just below its critical current, so that an impinging photon triggers a transition from the superconducting to the normal state, resulting in a voltage spike at the nanowire leads. Superconductivity is then recovered within a few nanoseconds.

The detection efficiency can be boosted close to 100% by coupling the superconducting nanowire to the evanescent field propagating in a waveguide. However, the fabrication of high quality, ultrathin superconducting layers is challenging (e.g. the critical temperature of superconducting NbN thin films on silicon is typically about 10 K, compared to 16 K for bulk NbN), and the operation wavelength of such devices is limited by the waveguide band gap.

We have identified GaN/AlN as the best suited waveguide material system, approximately lattice matched with NbN, and with a transparent band from 400 to 6000 nm. The target of the SuSiPOD project is the establishment of a technology platform for the fabrication of a new generation of broadband superconducting nanowire single-photon detectors built on III-nitride waveguides, in which photons are coupled laterally with the help of a tapered optical fibre. This new geometry should allow near-unity absorption probability in a wide spectral range, since the substrate is transparent to visible and infrared light. The project success will be proven by the realization of a working prototype which will greatly outperform state-of-the-art single-photon detectors.