Simultaneous mode conversion and wavelength routing in an SOI photonic integrated circuit

This paper proposes a multifunctional device integrating mode conversion and wavelength routing on a single chip. The device passively processes four wavelength–mode channels formed by two modes (TE 0 and TE 1 ) at two wavelengths (1,490 nm and 1,550 nm), which can be selectively routed to the device’s four different output ports. The device is built on a Silicon-on-Insulator (SOI) platform, including two main functional blocks: a mode conversion block using multimode interference (MMI-1 × 3 and MMI-3 × 2), and a wavelength routing block based on two butterfly structures (MMI-1 × 2). Structural parameters are refined using the three-dimensional beam propagation method (3D-BPM) to achieve suitable insertion loss and crosstalk performance. Simulation results show that at a wavelength of 1,490 nm, insertion loss and crosstalk are approximately 1.6 dB and −13 dB, respectively, while the corresponding values at 1,550 nm are approximately 1.7 dB and −15 dB. Furthermore, the device has a compact size of only 3.6 × 344.5 µm 2 . Fabrication tolerance analysis confirms that the device maintains stable operation for ±20 % variations in the investigated input-waveguide length ( L ᵢ n ) and width ( W ᵢ n ). The proposed passive device could be potentially suitable for CMOS-compatible photonic integrated circuits in MDM–WDM hybrid systems.