Ultra-Sharp Multimode Waveguide Bends Based on Superellipse Curves and Shallowly Etched Nanoslots Designed by an Intelligent Algorithm

As an emerging technique, mode division multiplexing (MDM) can effectively increase the data capacity in communication networks. High-performance multimode waveguide bends with small device footprints play an indispensable role in multimode photonics and MDM technique. Previously reported multimode waveguide bends still face the challenge of limited number of supported modes and relatively large device footprint. To tackle these challenges, based on the intelligent inverse design algorithm that combines adaptive genetic algorithm (AGA) and finite element method (FEM) simulation, a kind of multimode waveguide bend based on superellipse curves and shallowly-etched subwavelength nanoslots is proposed in this work. Numerical simulation results confirm that the multimode waveguide bends can support up to 5 TE modes and 8 TE/TM modes (4 TE + 4 TM), whose bending radius is only 3.55 and 3.25 μm, respectively. All devices can be characterized as ultra-sharp 90° multimode waveguide bends with low loss and low crosstalk. Moreover, this work reconfirms the good generality of our intelligent design methodology, which can be applied to the design and optimization of various photonic devices. Meanwhile, the proposed multimode waveguide bends hold good prospect in application of MDM techniques in multimode silicon photonics.