An SU-8 Waveguide System Coupled to Site-Controlled (In)GaAs QDs

In this work, we present a novel fabrication process tailored to pyramidal site-controlled quantum dots (QDs) for hybrid integration with polymer based photonic integrated circuits (PICs). Hybrid integration of III-V QDs with PICs is desirable for scaling up quantum communication nodes and to ease the generation of, e.g., large entangled states [1]. However, such integration remains challenging with unavoidable trade-offs between coupling efficiency, fabrication complexity, yield etc. Polymer waveguides offer cost-effective solutions with broad spectral windows and substrate independence, making them suitable for integrating heterogeneous photonic materials [2]. Despite many polymers becoming brittle at the cryogenic temperatures needed for quantum emitters, the epoxy based polymer SU-8 was successfully demonstrated as a robust waveguide material for cryogenic PICs [3]. For this work, we chose to use pyramidal QDs grown on pre-patterned GaAs substrates which provide large arrays of site-controlled emitters for single photon and entangled photon generation [4]. The a-priori knowledge of the QDs position provides a route to scalability with deterministic couplings.