Automated Characterisation of Integrated Photonic Components for Diamond-Based Quantum Systems

Abstract

To realize large-scale, optically accessible diamond-based spin quantum systems, heterogeneous integration is essential. This involves interconnecting and manipulating defect spin qubits in diamond photonic structures via intricate photonic components and circuits fabricated from materials like silicon nitride (SiN). This thesis develops and automates a characterisation setup for photonic components operating within the visible spectrum, suitable for characterising photonic components designed to implement and integrate in diamond spin quantum systems. The main goal being achieving a transmission efficiency of more than 0.2% for the provided silicon nitride waveguides. The setup is capable of measuring power and spectral response with high precision, achieving transmission loss measurements up to 3 dB/cm, limited by current waveguide/photonic component performance, and a positional accuracy of less than 100 nm. Using silicon nitride waveguides coupled with grating couplers, transmission loss measurements were obtained that closely matched previous results, validating the setup’s accuracy. To further validate the setup, a transmission efficiency of up to 3.2% was achieved for the silicon nitride waveguides, which is more than 10 times higher than results from a comparable setup. Automated measurements show below a minute measurement time per device, enabling efficient and repeatable testing. Furthermore, the Pick and Place diamond waveguide showed a transmission of 1.7 μW with an input power of 2.75 mW. This was a first in our research group and validates the performance of the characterisation setup as well. This automated setup thus provides a scalable solution for rapid photonic component evaluation, addressing integration challenges in diamond-based quantum architectures by improving measurement throughput and coupling efficiency.