Waveguide-integrated colour centres in silicon carbide with broadband photonic crystal reflectors for efficient readout

The article focuses on the design, fabrication, and characterization of waveguide-integrated colour centres in silicon carbide (SiC) with broadband photonic crystal reflectors to enhance photon collection efficiency for quantum applications. The integration of V2 silicon vacancy colour centres into these structures aims to improve photon count rates and enable high-fidelity optical single-shot readout of electron spins.

Key findings:

1. Waveguide-Integrated Reflectors: The paper introduces "Dinosaur" photonic crystal reflectors integrated with waveguides. These structures offer broadband reflection across a 60 THz range with peak reflectance above 80%, significantly improving photon collection efficiency compared to traditional methods.

2. Device Characterization: The reflectors were tested at cryogenic temperatures (~10 K). The integration of V2 colour centres led to photon count rates exceeding 100 kcps in standard photoluminescence excitation (PLE) measurements, which is an order of magnitude higher than bulk emitters. This improvement is achieved by coupling the photon emission into a tapered-waveguide-tapered-fibre (TWTF) interface.

3. Saturation Intensity and Single-Shot Readout: The study reported a saturation intensity of 103.8 ± 4.2 kcps in PLE measurements. When using a charge-resonance check (CRC) method, the count rate could be increased to approximately 125 kcps. The study also explores the feasibility of optical single-shot readout (SSR) of the electron spin. Under ideal conditions, the fidelity of SSR reached 98.44%, indicating the potential of the device for high-performance quantum measurements.

4. Simulation and Fabrication: The paper details the fabrication of the reflectors using electron-beam lithography, reactive ion etching, and other methods. The Dinosaur reflector's performance was measured and compared to simulations, showing a spectral operating range of approximately 59 THz, with an average reflectance of 64.5 ± 10.6%. These results validate the device's efficiency for photon collection.

Conclusion:

The integration of V2 colour centres into SiC waveguides with Dinosaur photonic crystal reflectors represents a significant advancement in quantum photonics. This work demonstrates an efficient method for photon collection and single-shot readout, which is a critical step toward realizing high-fidelity quantum applications. The device is poised to play a key role in the development of scalable quantum networks and other quantum technologies.