Compact four-port optical mode router based on direct mode-selective coupling.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Mode-division multiplexing (MDM) is crucial for increasing optical interconnect capacity.
• Scalable multimode photonic integrated circuits require efficient mode routing and add-drop functionality.
• Challenges exist in creating compact, low-loss, low-crosstalk silicon photonic mode routers.

Purpose of the Study:

• To propose and experimentally demonstrate a novel compact four-port optical mode router.
• To enable mode-selective and bidirectional add-drop routing for multiple modes on a silicon photonic platform.
• To address the limitations of existing mode router designs.

Main Methods:

• Integration of multimode waveguide crossings, bends, and mode-selective microring resonators.
• Careful design of mode-matching and multimode waveguide engineering for low loss and crosstalk.
• Experimental validation on a silicon-on-insulator platform.

Main Results:

• Successful demonstration of a compact four-port optical mode router.
• Achieved mode-selective routing for three supported modes.
• Reported inter-mode crosstalk below -15.4 dB and insertion loss below 6.6 dB.
• Demonstrated high-speed data transmission at 40 Gbit/s per path, yielding an aggregate capacity of 480 Gbit/s.

Conclusions:

• The proposed architecture offers a scalable solution for high-capacity MDM optical interconnects.
• The device overcomes key challenges in silicon photonic mode router implementation.
• This work paves the way for advanced multimode photonic integrated circuits.