Ultra-compact multimode waveguide bend based on a central width controllable dual Bezier structure.

Abstract

Multimode waveguide bend (MWB) with compactness and high performance is essential for modern mode-division multiplexing (MDM) systems. Here, we present a four-mode MWB optimization method, allowing for direct optimization of the bend's central width, enabling precise control of the MWB's overall curvature variation and preventing excessive narrowing of the waveguide width to suppress loss. The realized bending effective radius is 10 μm, equivalent to the most compact design to date, while being based on a simpler method using dual Bezier mathematical curves. The calculated excess losses demonstrate very low rates of 0.0114, 0.0111, 0.0047, and 0.0310 dB for the first four TE modes at 1550 nm, representing the best transmission efficiency. Notably, there is a significant improvement in the performance of high-order mode, which was previously considered challenging at such a small size.