Deterministic Integration of Quantum Emitters by Direct Laser Writing using Two-Photon Polymerization
A major challenge towards integrated quantum optics is the deterministic integration of quantum emitters on optical chips. Combining the quantum optical properties of some emitters with the benefits of integration and scalability of integrated optics is still a major issue to overcome. In this work, we demonstrate a novel approach in which quantum emitters are positioned in a controlled manner onto a substrate and onto an optical waveguide with nanoscale precision via direct laser writing based on two-photon polymerization (DLW-TPP). Our quantum emitters are colloidal CdSe/ZnS quantum dots (QDs) embedded in polymeric nanostructures. Varying the laser parameters during the patterning process, size-controlled QD-polymer nanostructures have been characterized systematically. Structures as small as 20 nm in height were fabricated. The well-controlled QD-polymer nanostructure systems were then successfully integrated at will onto a photonic platform, in our case, ion exchange waveguide (IEW). We show that our quantum dots maintain their high light emitting quality after integration as verified by photoluminescence (PL) measurements. Ultimately, QD emission coupled to our waveguides is detected through a home-build fiber-edge coupling PL measurement setup. Our results show the potential for future quantum optical communications and pave a novel way towards top-down deterministically integrating quantum emitters onto complex photonic chips.