Fiber-to-Chip Three-Dimensional Silicon-on-Insulator Edge Couplers with High Efficiency and Tolerance

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Edge couplers are critical for integrating external fibers with on-chip waveguides in optical circuits.
• Coupling efficiency directly impacts the performance and integration capabilities of photonic devices.
• Existing edge coupler designs often face limitations in efficiency and tolerance.

Purpose of the Study:

• To propose and experimentally validate novel three-dimensional (3D) edge couplers.
• To achieve high coupling efficiency and enhanced misalignment tolerance for fiber-to-chip connections.
• To explore the potential of 3D grayscale lithography for fabricating advanced optical components.

Main Methods:

• Theoretical calculations were performed to verify the high coupling efficiency of the proposed 3D edge couplers.
• Three distinct 3D edge coupler designs were fabricated using 3D grayscale lithography on a thick-silicon platform.
• Experimental measurements were conducted at the 1550 nm wavelength band to assess coupling efficiency and misalignment tolerance for both TE and TM modes.

Main Results:

• Maximum coupling efficiencies of -0.70 dB/-1.34 dB, -0.80 dB/-1.60 dB, and -1.00 dB/-1.14 dB were achieved for TE/TM modes, respectively.
• Misalignment tolerance measurements demonstrated ±5 μm horizontal tolerance (0.8 dB/0.9 dB for TE/TM) and ±2 μm vertical tolerance (1.7 dB/1.0 dB for TE/TM).
• The fabricated 3D edge couplers exhibited significant superiority compared to conventional designs.

Conclusions:

• The study successfully demonstrates high-efficiency and high-tolerance 3D edge couplers fabricated via 3D grayscale lithography.
• These results offer a promising new approach for the design of edge couplers in optical communication and integration.
• The developed 3D edge couplers show significant potential for both research and industrial applications in photonics.