Heterogeneous integration of silicon nitride and amorphous silicon carbide photonics

This paper presents the heterogeneous integration of amorphous silicon carbide (a-SiC) and silicon nitride (SiN) photonics, combining the benefits of both materials to overcome their respective limitations. The integration results in a photonic platform with ultra-low loss, high integration density, and enhanced thermo-optic tunability, making it ideal for a wide range of applications in integrated photonics, quantum photonics, and nonlinear optics.

Key findings include:

1. Advantages of SiN and a-SiC: SiN offers low propagation loss and is widely used for photonic devices, but its large minimum bending radius and limited tunability pose challenges. a-SiC, on the other hand, provides high refractive index, strong third-order nonlinearities, and excellent thermo-optic properties, making it highly suitable for active photonic devices.

2. Integration Process: The study achieved the heterogeneous integration of a-SiC with SiN on a chip, with an interconnection loss of just 0.32±0.10 dB. The integration significantly enhances the integration density by over 4,444 times compared to conventional SiN-only platforms.

3. Thermo-optic Tuning: a-SiC-based devices demonstrated 27 times higher thermo-optic tuning efficiency than SiN, with a thermo-optic coefficient of 5.1×10−5/°C for a-SiC and 3.6×10−5/°C for SiN, enabling more efficient and scalable tunable photonic circuits.

4. Fiber-to-chip Coupling: Both side-coupling and grating-coupling methods were optimized for the integrated platform, with side-coupling providing 55 times higher coupling efficiency compared to standard SiN waveguides, and grating-coupling proving effective for wafer-scale production.

5. Applications: The proposed a-SiC/SiN platform opens up possibilities for various photonic applications, including programmable and quantum photonics, nonlinear optics, and on-chip single-photon sources, as well as high-performance delay lines for integrated photonic computing.

In conclusion, this work demonstrates that the integration of a-SiC and SiN on a single photonic platform addresses key limitations of individual materials, offering a highly tunable, low-loss, and scalable solution for advanced photonic applications.