Subwavelength engineering and asymmetry: two efficient tools for sub-nanometer-bandwidth silicon Bragg filters

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Bragg filters are crucial for silicon-on-insulator (SOI) photonics, enabling on-chip signal manipulation.
• Fabrication constraints often limit achieving narrowband Bragg filters with high rejection levels.

Purpose of the Study:

• To investigate subwavelength engineering and single-side corrugation asymmetry for improved SOI Bragg filters.
• To overcome minimum feature size limitations in conventional silicon (Si) Bragg filters.

Main Methods:

• Comprehensive study of corrugation asymmetry in conventional and subwavelength single-etched SOI Bragg filters.
• Experimental demonstration of a novel subwavelength geometry with shifted corrugation teeth.

Main Results:

• Corrugation asymmetry and subwavelength engineering significantly reduce bandwidth.
• Demonstrated null-to-null bandwidths of 0.8 nm (40 dB rejection) for symmetric and 0.6 nm (15 dB rejection) for asymmetric configurations.

Conclusions:

• Subwavelength engineering combined with asymmetric corrugations offers a viable path to narrowband SOI Bragg filters.
• The novel subwavelength geometry effectively addresses fabrication constraints for enhanced filter performance.