The realization of novel and telecom-compatible optoelectronic devices for fiber-based quantum communication is the focus of this project. The key technologies include single photon sources (EPQ) based on single quantum dots (QPs) with optical and electrical excitation and advanced vertical emitting lasers (VECSELs) in the 1.3 µm wavelength range. The overall goal of the project is to combine these two key technologies. A highly efficient EPQ emitting indistinguishable photons in the telecom O-band (1.3 µm) will be realized, resonantly pumped by an electrically driven VCSEL. This approach paves the way for a compact and practical EPQ based solely on semiconductor technology.

The QP structures are deposited on a bottom distributed Bragg reflector (DBR) and a dielectric layer structure is deposited on top to form a microcavity. The dielectric layers are also laterally structured to enable easy and highly efficient coupling of single photons into single-mode waveguides or single-mode optical fibres in the future. For the structuring of the lower part of the microcavities, a unique in-situ cryogenic electron beam lithography technique is used to precisely position individual and pre-selected QDs within the mesa, thus achieving optimal device functionality. In order to be able to drive the QDs resonantly and at high speed, high-speed VCSELs are fabricated in the wavelength range around 1.3 µm. Both a GaAs-based monolithic process and an InP-based wafer fusion approach are used, which are evaluated in terms of better performance. The finished structures will be investigated and tested by means of quantum-optical experiments, whereby above all the most important properties will be recorded with regard to the planned applications. These include the emission dynamics / rate, the photon extraction efficiency, the purity of the single-photon emission and the indistinguishability of the single photons.