Goal of research: Development of superconducting single-photon detectors on optical waveguides of silicon nitride and silicon oxide, research into maximum possible performance of such detectors and methods of their optimization for specific applications.
Methodology: Mathematical modeling and simulation of optimal optical waveguide and optimization of single photon detectors was performed with COMSOL package and finite elements method.
Fabrication process was based on electron-beam lithography with high resolution electron resist ZEP520A and reactive ion etching (RIE). We used Si/SiO2/Si3N4 wafers. The quality of the waveguides was tested by the measurement of their optical transmission.
Characterization of single-photon detectors was based on the measurement of the quantum efficiency, dark count rate, count rate and timing jitter. The measurements were performed at liquid helium temperatures. As the light source we used light emitting diodes (LED) of visible and infrared range. Photon counts were measured by electronic pulse counter.
Empirical base of research: The subject of the research is the planar optical waveguides, waveguide optical elements (beam splitters, filters, interferometers, etc), single-photon detectors integrated with the waveguides. The state-of-the-art quantum optics requires more and more complex optical schemes. The traditional approach based on the assembling of the set-up from the unitary elements on the optical table becomes less and less fruitful. Optical integrated circuits are the most prospective approach to this problem that provides cheap and scalable solution. Presently passive optical on-chip elements such as waveguages, beam splitters, mirrors, directional dividers are well developed, and the problem is how to integrate on chip passive optical elements and single-photon detectors. Superconducting single-photon detectors are CMOS-compatible and cam be fabricated by a processes used in semiconductor industry.
Results of research: in theory - we have developed a model of interaction of running electromagnetic wave in the dielectric waveguide with the narrow superconducting strip on the top of such waveguide comprising a superconducting single-photon detector;
in methodology development - (1) we have developed a method of simulation of the optimal configuration of the optical waveguides, (2) we have developed methods of fabrication of single-photon detectors and optical waveguides, (3) we have developed method of waveguide single-photon detector characterization: measurement of quantum efficiency, dark count rate, timing jitter;
in acquisition of new empirical knowledge - (1) we have fabricated superconducting single-photon detectors on optical waveguides, (2) the performance of this detectors is experimentally measured, (3) we compared results of the experiments with the modelling predictions;
intellectual activity results - new scientific results are published in scientific journals.
Level of implementation, recommendations on implementation or outcomes of the implementation of the results. The technology of nanophotonic waveguides can be used for fabrication of optical integrated circuits used in the scalable system of quantum logic. Single-photon receivers based on optical waveguides with single-photon detectors can be used in (a) biological imaging systems, (b) spectroscopy of correlated photons emitted by single molecules, (c) in dynamic optical reflectometry and tomography, (d) in non-invasive testing of semiconductor large integrated circuits by detection of photons emitted by switching field-effect transistors, (e) registration of weak fluxes of photons with high temporal resolution, (f) in metrology for power measurement by single-photon counting, (g) in quantum cryptography.