Wide bandwidth and high coupling efficiency Si3N4-on-SOI dual-level grating coupler

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Materials Science

Background:

• Fiber-to-chip coupling is crucial for optical interconnects.
• Existing grating couplers face limitations in bandwidth and efficiency.
• Silicon nitride (Si3N4) and silicon (Si) are key materials in integrated photonics.

Purpose of the Study:

• To demonstrate high-performance fiber-to-chip grating couplers.
• To achieve wide bandwidths and high coupling efficiencies.
• To integrate these couplers into a silicon nitride on silicon-on-insulator (SOI) platform.

Main Methods:

• Fabrication of dual-level grating couplers with aligned Si3N4 and Si grating teeth.
• Experimental characterization of coupling efficiency and 1-dB bandwidth.
• Integration with silicon microring resonators for device demonstration.

Main Results:

• Record 80 nm 1-dB bandwidth achieved.
• Peak coupling efficiency of -1.3 dB, competitive with Si-only couplers.
• Successful demonstration of a 1x4 tunable multiplexer/demultiplexer.

Conclusions:

• The proposed dual-level grating couplers offer superior performance without bottom reflectors.
• This technology enables advanced integrated photonic devices on Si3N4-on-SOI platforms.
• The results pave the way for more efficient optical communication systems.