Ultra-compact mode (de) multiplexer based on subwavelength asymmetric Y-junction

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Nanophotonics

Background:

• Mode-division multiplexing (MDM) is crucial for increasing optical communication capacity.
• Existing mode (de)multiplexers often lack the compactness required for highly integrated systems.
• Subwavelength structures offer unique optical properties for miniaturized devices.

Purpose of the Study:

• To propose and demonstrate a novel ultra-compact mode (de)multiplexer.
• To enable efficient on-chip mode-division multiplexing for integrated photonic systems.
• To achieve low insertion loss and crosstalk in a small footprint.

Main Methods:

• Design of an asymmetric Y-junction with a wide divergence angle.
• Optimization using an inverse design method.
• Fabrication and experimental characterization of the device.

Main Results:

• Demonstrated an ultra-compact mode (de)multiplexer with a footprint of 2.4 × 3 µm².
• Achieved insertion loss < 1 dB and crosstalk < -24 dB for TE0 and TE1 modes from 1530 nm to 1590 nm.
• Designed and fabricated a three-mode multiplexer with a footprint of 3.6 × 4.8 µm².

Conclusions:

• The proposed device is highly suitable for integrated mode-division multiplexing systems.
• The design demonstrates excellent performance in terms of size, loss, and crosstalk.
• The scheme is scalable to multiplexing a higher number of modes.