GLINT · Generation of Nonclassical States of Light in Silicon Nitride Photonics by Second-Order Nonlinearity

Harnessing the quantum properties of light on-chip is the ultimate aim of Integrated Quantum Photonics, bearing the promise of novel quantum technology functionalities to the microscale. A critical step in this process is the generation of quantum light, typically achieved through nonlinear processes such as spontaneous parametric down-conversion (SPDC) in second-order (χ(2)) nonlinear media or spontaneous four-wave mixing (SFWM), through the third-order (χ(3)) response. While the silicon nitride (SiN) integrated photonics platform has proven extremely reliable, low-loss, and compatible with large scale fabrication, its centrosymmetric nature of SiN prevents χ(2) interactions, hindering the implementation of low-noise, highly efficient SPDC-based sources. Lithium Niobate and III-V materials are valid alternatives, but they lack the technological maturity provided by the CMOS fabrication process. Recent research has shown that the coherent photogalvanic effect can endow SiN with a χ(2) response, a photoinduced nonlinearity that automatically satisfies the quasi-phase matching condition, enabling highly efficient frequency conversion. Such “all-optical poling” technique has proven suitable to enable a wide range of functionalities based on χ(2) interactions. The purpose of GLINT is to investigate the potential of all-optical poling in SiN for the generation of quantum light via χ(2) processes. The project will specifically focus on the study of SiN microring-resonator-based SPDC sources, owing to their capability to enhance the efficiency of spontaneous processes and to generate, thanks to their peculiar spectral response, narrow-band states. This will be achieved by i) theoretically modelling a resonator-based SPDC source ii) realizing a chip-scale prototype using commercial-grade technology and providing a full characterization of the generated quantum states iii) demonstrating a proof-of-concept quantum communication protocol using the developed chip-scale source.