Design of an efficient and broadband adiabatic mode-converting splitter for TE0-to-TE1 splitting

We propose and numerically demonstrate a compact and broadband adiabatic mode conversion splitter (AMCS) on the silicon-on-insulator platform. The device is engineered to convert the fundamental TE0 mode in the input single silicon waveguide into the TE1 even supermode of the output dual-waveguide system, resulting in an equal power distribution (≈50%) between the two output silicon waveguides. By leveraging a carefully optimized adiabatic mode evolution mechanism, the design minimizes mode-mismatch and scattering losses. Simulation results, obtained via the eigenmode expansion (EME) method, show a high power transfer efficiency of 90% for a compact device length of only 240 μm at a 1550 nm wavelength. Furthermore, a device with a length of 276 μm exhibits an operating bandwidth of 120 nm (from 1463 to 1583 nm) while maintaining over 90% efficiency. This performance represents a significant improvement in bandwidth compared with previously reported designs. Its low loss, compact footprint, and broad bandwidth make the proposed AMCS a highly promising component for advanced photonic integrated circuits, including mode-division multiplexing systems and optical phased arrays.