Low-loss and low-crosstalk multimode waveguide bend on silicon.

Area of Science:

• Photonics
• Optical Engineering
• Integrated Optics

Background:

• Mode-division multiplexing (MDM) is essential for increasing optical interconnect capacity.
• Traditional waveguide bends suffer from high loss and crosstalk, limiting device miniaturization.

Purpose of the Study:

• To propose and demonstrate a low-loss, low-crosstalk multimode waveguide bend for MDM optical interconnects.
• To enable compact and efficient photonic integrated circuits.

Main Methods:

• Design of a 90° bend using modified Euler curves (two cascaded 45° bends).
• Fabrication and characterization of a silicon photonic integrated circuit featuring the Euler S-bend.
• Analysis of excess loss and inter-mode crosstalk for TM-polarized modes.

Main Results:

• The proposed 90° Euler-bend allows for an effective radius of 45 μm, a 75% reduction compared to regular arc-bends.
• Theoretical predictions show excess losses <0.1 dB and inter-mode crosstalks <-25 dB.
• Fabricated Euler S-bends exhibit measured excess losses <0.5 dB and inter-mode crosstalks <-20 dB across a 1520-1610 nm bandwidth for 4 TM mode-channels.

Conclusions:

• The demonstrated Euler waveguide bend is a viable solution for compact and high-performance MDM optical interconnects.
• This technology facilitates miniaturization of photonic devices without compromising signal integrity.