[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Deterministic Integration of Quantum Dots into On-Chip Multi-Mode Interference Couplers Via in-Situ Electron Beam Lithography

摘要： On-chip quantum optical circuits offer superior performance and scalability compared to bulky optical setups. Additionally, the up-scaling of quantum systems will foster the realization of photonic quantum computers to outperform their classical counterparts. In this context, the deterministic integration of quantum emitters into on-chip photonic elements is crucial for the implementation of scalable on-chip quantum circuits. Recent activities in this field include hybrid QD-waveguides for enhanced photon in-coupling [1] and first, rather tedious steps towards the controlled integration of QDs using multistep-lithography [2] as well as AFM tip transfer [3]. Here we report on the deterministic integration of single quantum dots (QD) into on-chip beam splitters using in-situ electron beam lithography (EBL) [4]. In this single-step technique, photonic building blocks are patterned by means of EBL on top of chosen QDs immediately after spatially and spectrally pre-characterizing QDs by means of cathodoluminescence mapping at cryogenic temperatures (~10 K) [5]. The used in-situ EBL technology platform allows for the realization of complex on-chip quantum circuits with high process yield (see Fig. 1(a-d)). To underline the high potential of this method we realize 50/50 coupling elements connected to waveguide sections with deterministically integrated QDs (see Fig. 1(e)). The couplers act as central building blocks of on-chip quantum circuits and we chose a robust design based on tapered multimode interference (MMI) splitters which feature relaxed fabrication tolerances and a constant 50/50 splitting ratio. We demonstrate the functionality of the deterministic QD-waveguide structures by high-resolution μPL spectroscopy and by studying the photon cross-correlation between the two MMI output ports (Port 1 and Port 2 in Fig. 1(e)). The latter confirms single-photon emission and on-chip splitting associated with g(2)(0) < 0.5. Present work focusses on the deterministic realization of heterogeneous integrated quantum photonic devices and multi-QD quantum circuits allowing for on-chip Hong-Ou-Mandel experiments.