Effective integration of highly-efficient focusing apodized grating and quantum dots on a solid substrate for scalable quantum photonic circuits

Recent advancements in quantum photonic circuits have significantly influenced the field of quantum information processing.The pursuit of an integrated quantum photonic circuit that offers an active,stable platform for large-scale integration and high processing efficiency remains a key objective.The grating coupler,as a crucial element for an efficient transformation output interface in the integrated quantum photonic circuits,presents significant potential for practical applications.Here,we demonstrate the integration block of a highly efficient shallow-etched focusing apodized grating coupler with indium arsenide(InAs)quantum dots(QDs)in gallium arsenide(GaAs)on a SiO2substrate for active quantum photonic circuits.The designed grating couplers possess a high efficiency over 90% in the broadband(900-930 nm)from the circuit to free space,and a nearly-perfect match with the fiber mode.Experimentally,the efficiency to free space reaches 81.8%,and the match degree with the fiber mode is high up to 92.1%.The proposed integration block offers the potential for large-scale integration of active quantum photonic circuits due to its stable solid substrate and highly performant output for quantum measurements.

Bright semiconductor single-photon sources pumped by heterogeneously integrated micropillar lasers with electrical injections

The emerging hybrid integrated quantum photonics combines the advantages of different functional components into a single chip to meet the stringent requirements for quantum information processing.Despite the tremendous progress in hybrid integrations of III-V quantum emitters with silicon-based photonic circuits and superconducting single-photon detectors,on-chip optical excitations of quantum emitters via miniaturized lasers towards single-photon sources(SPSs)with low power consumptions,small device footprints,and excellent coherence properties is highly desirable yet illusive.In this work,we present realizations of bright semiconductor SPSs heterogeneously integrated with on-chip electrically-injected microlasers.Different from previous one-by-one transfer printing technique implemented in hybrid quantum dot(QD)photonic devices,multiple deterministically coupled QD-circular Bragg Grating(CBG)SPSs were integrated with electrically-injected micropillar lasers at one time via a potentially scalable transfer printing process assisted by the wide-field photoluminescence(PL)imaging technique.Optically pumped by electrically-injected microlasers,pure single photons are generated with a high-brightness of a count rate of 3.8 M/s and an extraction efficiency of 25.44%.Such a high-brightness is due to the enhancement by the cavity mode of the CBG,which is confirmed by a Purcell factor of 2.5.Our work provides a powerful tool for advancing hybrid integrated quantum photonics in general and boosts the developments for realizing highly-compact,energy-efficient and coherent SPSs in particular.

Scalable and highly efficient approach for an on-chip single-photon source

Integrated photonic circuits with quantum dots provide a promising route for scalable quantum chips with highly efficient photonic sources.However,unpolarized emission photons in general sacrifice half efficiency when coupling to the waveguide fundamental mode by a cross polarization technique for suppressing the excitation laser,while suspended waveguide photonics sources without polarization filters have poor scalability due to their mechanical fragility.Here,we propose a strategy for overcoming the challenge by coupling an elliptical Bragg resonator with waveguides on a solid-state base,featuring near-unity polarization efficiency and enabling on-chip pulsed resonant excitation without any polarization filters.We theoretically demonstrate that the proposed devices have outstanding performance of a single-photon source with 80%coupling efficiency into on-chip planar waveguides and an ultra-small extinction ratio of 10-11,as well as robustness against quantum dot position deviation.Our design provides a promising method for scalable quantum chips with a filter-free high-efficiency single-photon source.