Inverse-designed ultra-compact multi-channel and multi-mode waveguide crossings.

Area of Science:

• Photonics and Waveguide Technology
• Integrated Optics
• Nanophotonics

Background:

• Waveguide crossings are essential components in integrated photonic circuits.
• Efficiently routing multiple modes (TE0 and TE1) through crossings is challenging.
• Existing designs often suffer from high insertion loss and crosstalk.

Purpose of the Study:

• To design and experimentally validate novel three- and four-channel dual-mode waveguide crossings.
• To achieve efficient propagation of both fundamental transverse electric (TE0) and first higher-order transverse electric (TE1) modes.
• To minimize insertion loss and crosstalk for broadband operation.

Main Methods:

• Utilized inverse design methodology for optimizing waveguide structures.
• Designed waveguide crossings with hexagonal and octagonal cross-sections.
• Fabricated the designed devices using standard nanofabrication techniques.
• Experimentally characterized device performance, including insertion loss and crosstalk.

Main Results:

• Achieved low insertion losses (<1.8 dB for three-channel, <2.5 dB for four-channel devices) for both TE0 and TE1 modes.
• Demonstrated excellent crosstalk suppression (< -18.4 dB for three-channel, < -17.0 dB for four-channel devices).
• Experimental results validated the designs across a wavelength range of 1540 nm to 1560 nm.

Conclusions:

• The inverse design approach enables the creation of high-performance dual-mode waveguide crossings.
• The proposed designs offer efficient mode multiplexing and demultiplexing capabilities.
• The scheme is scalable to waveguide crossings with more channels and modes, paving the way for advanced photonic integrated circuits.