On-chip microlaser driven sources of indistinguishable photons for quantum networks

• Applicants: Dr. Tobias Huber-Loyola; Professor Dr. Stephan Reitzenstein
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449930472

This project aims at developing highly integrated quantum light sources based on semiconductor quantum dots. Our device concept goes well beyond existing approaches by using monolithically integrated microlasers to resonantly trigger the emission of indistinguishable photons from quantum dots. Being electrically driven the microlasers combine user-friendly operation with ultra-small footprint. Moreover, compared to solutions for electrically driven quantum light sources based on simple carrier injection via a p-i-n junction, our advanced on-chip resonant excitation scheme ensures excellent quantum nature of emission in terms of multi-photon suppression and photon indistinguishability. To meet the challenging technological requirements of our concept we apply state-of-the-art nanoprocessing and deterministic device technology. This way we realize low threshold whispering gallery microlasers whose emission is evanescently coupled into ridge waveguide systems with deterministically integrated quantum dots. Here, in-situ electron beam lithography ensures that quantum dots with suitable wavelength matched to the emission wavelength of the microlaser are located at waveguide positions with maximum coupling efficiency into the target waveguide mode. The waveguide systems include splitting elements, resonators to control the emission dynamics and to maximize the photon extraction efficiency, as well as non-linear elements for on-chip frequency conversion of single photons to telecom wavelengths at 1.55 micrometers. Overall, our project creates the foundations for complex and highly functional quantum circuitry to act as important building blocks for future quantum communication and quantum computation systems.

• DFG Programme: Research Grants
• International Connection: Austria
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partner: Professor Dr. Gregor Weihs