Compact high extinction ratio high-order mode pass filter based on inverse-designed ultra-compact unidirectional mode...

Area of Science:

• Photonics and Optical Communications
• Integrated Optics

Background:

• Mode division multiplexing (MDM) is key for next-generation optical networks, but requires effective mode control.
• Low-order mode suppression is a significant challenge in MDM system development.
• Mode filters are critical components for reducing modal crosstalk and enabling practical MDM.

Purpose of the Study:

• To introduce and demonstrate a novel high-order mode pass filter (HOMPF) strategy.
• To address the challenge of effectively blocking low-order modes in MDM systems.
• To present a compact and efficient solution for mode manipulation on a silicon-on-insulator platform.

Main Methods:

• Utilized inverse design for an ultra-compact unidirectional TE0-TE1 mode converter.
• Implemented a high-order mode pass strategy using unidirectional mode converters.
• Fabricated and experimentally validated a TE1 HOMPF on a silicon-on-insulator platform.

Main Results:

• Achieved a TE1-TE1 insertion loss below 1.0 dB.
• Demonstrated an average TE0-TE0 extinction ratio of 36.8 dB (42.1 dB for cascaded filters).
• Explored scalability with simulations of a TE2 HOMPF, confirming device potential.

Conclusions:

• The proposed HOMPF offers a simple, compact, low-loss, and high-extinction-ratio solution.
• This technology is a promising component for advanced mode manipulation in MDM systems.
• The demonstrated HOMPFs significantly enhance the feasibility of high-capacity optical communication systems.