Inverse design fiber-to-chip couplers for the O- and C-bands

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• High-efficiency fiber-to-chip couplers are critical for advanced optical interconnects.
• Existing solutions often face limitations in size, efficiency, or fabrication complexity.
• Silicon-on-insulator (SOI) technology offers a promising platform for integrated photonics.

Purpose of the Study:

• To experimentally demonstrate novel, inverse-designed SOI couplers for C and O telecommunication bands.
• To achieve high coupling efficiency and broad bandwidth in compact devices.
• To present the first topology-optimized O-band coupler with a 120 nm minimum feature size.

Main Methods:

• Utilized inverse design and topology optimization for coupler design.
• Fabricated devices on a single optimized silicon layer for reduced complexity.
• Experimental characterization of coupling efficiency and 3-dB bandwidth for both C and O bands.

Main Results:

• Demonstrated two SOI couplers operating at an 8° angle for TE polarization.
• Achieved -3.3 dB efficiency with 64 nm bandwidth (C-band) and -3.4 dB efficiency over 1292-1355 nm (O-band).
• Devices measure 12 μm x 12 μm, offering efficiencies comparable to larger grating couplers.

Conclusions:

• The developed compact couplers provide high performance for optical interconnects.
• Their small footprint enhances integration density and reduces fabrication costs.
• Potential applications include spatial division multiplexing and multimode fiber configurations.