Highly efficient and perfectly vertical chip-to-fiber dual-layer grating coupler

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Semiconductor Device Physics

Background:

• Efficient light coupling between silicon chips and optical fibers is essential for integrated photonic circuits.
• Traditional coupling methods face challenges in achieving high efficiency and low back reflection.
• The development of advanced grating couplers is critical for next-generation optical communication systems.

Purpose of the Study:

• To investigate a novel high-efficiency silicon-chip-to-fiber grating coupler.
• To demonstrate perfectly vertical coupling using a dual-layer grating structure.
• To analyze the coupling efficiency and back reflection across the telecom C-band.

Main Methods:

• Design and simulation of a dual-layer grating coupler with an inter-layer lateral shift.
• Mimicking 45° tilted mirror behavior for vertical light coupling.
• Numerical analysis of coupling efficiency and back reflection near 1550 nm and across the telecom C-band (1530-1565 nm).

Main Results:

• Achieved a peak silicon-chip-to-fiber coupling efficiency of approximately 70% near 1550 nm.
• Demonstrated coupling efficiency greater than 50% across the entire telecom C-band.
• Maintained back reflection below 1% for the proposed structure.

Conclusions:

• The novel dual-layer grating coupler enables high-performance, perfectly vertical light coupling.
• The demonstrated performance is suitable for interfacing with multi-core fiber platforms.
• This technology holds significant potential for advancing CMOS photonic integration.