Ultra-low-loss polarization-splitting grating coupler based on inverse-design

Area of Science:

• Silicon photonics
• Integrated optics
• Nanophotonics

Background:

• Polarization-splitting grating couplers (PSGCs) are essential for silicon photonic integrated circuits (PICs).
• Efficiently coupling light for both polarizations from optical fibers to PICs is critical.
• Existing PSGCs often face challenges in fabrication tolerance and performance.

Purpose of the Study:

• To propose and design a high-performance PSGC using an inverse design method.
• To achieve superior insertion loss (IL) and polarization-dependent loss (PDL) on silicon-on-insulator (SOI) platforms.
• To enable fabrication via a single etching step with high tolerance and reduce packaging costs.

Main Methods:

• Utilized an inverse design approach for optimizing the PSGC structure.
• Focused on a 220nm silicon-on-insulator (SOI) platform for device realization.
• Experimental characterization of the fabricated PSGC performance.

Main Results:

• Achieved a peak insertion loss (IL) of -1.05 dB and polarization-dependent loss (PDL) of 0.04 dB at 1534.7 nm.
• Demonstrated 1-dB bandwidths of 48 nm for IL and 68 nm for PDL.
• Verified single-etch fabrication with excellent fabrication tolerance and 0-degree fiber injection capability.

Conclusions:

• The proposed PSGC represents a significant advancement in silicon photonic components.
• The device offers state-of-the-art performance with reduced manufacturing complexity and packaging costs.
• This PSGC is suitable for advanced PIC applications requiring efficient dual-polarization light coupling.