Multimode silicon photonic waveguide corner-bend.

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Electrical Engineering

Background:

• Multimode waveguides are crucial for high-capacity optical communication systems.
• Efficient and compact waveguide bends are essential for integrated photonic circuits.
• Existing multimode waveguide bends often suffer from high losses or crosstalk.

Purpose of the Study:

• To propose and realize an ultra-sharp multimode waveguide bend (MWB) with low excess loss (EL) and inter-mode crosstalk (CT).
• To demonstrate the performance of the MWB across a broad wavelength range for optical communication bands.
• To highlight the design flexibility and fabrication simplicity of the proposed MWB.

Main Methods:

• Utilizing total internal reflection (TIR) within a multimode waveguide corner-bend (MWCB) structure.
• Designing the MWCB for specific TE modes (TE0 and TE1) and evaluating performance.
• Extending the design to accommodate multiple TE-polarization modes (TE0-TE9) by adjusting core width.
• Characterizing EL and CT across the 1260-1680 nm wavelength band.

Main Results:

• The MWCB achieves EL < 0.18 dB and CT < -36 dB for TE0 and TE1 modes from 1260-1680 nm.
• A 35 µm-wide core MWCB shows EL < 0.54 dB and CT < -24 dB for ten TE modes (TE0-TE9) in the same band.
• The fabricated MWCB performs as predicted, with low sensitivity to sidewall angles up to 8°.

Conclusions:

• The proposed MWCB offers excellent performance with low loss and crosstalk in an ultra-broadband wavelength range.
• The design is highly flexible for accommodating various numbers of mode channels.
• The simple structure, ease of design, and fabrication make the MWCB a promising solution for multimode silicon photonics.