On‐Chip Multi‐Mode Manipulation via 2D Refractive‐Index Perturbation on a Waveguide

Abstract Generation and manipulation of optical modes are of general interest to the photonics community. Mode conversion is an essential requirement in mode‐division multiplexed systems. In this paper, a scalable method to simultaneously manipulate multiple waveguide modes on chip is proposed. As one experimental demonstration, simultaneous multi‐mode conversion processes have been achieved on a waveguide. The device is realized via an all‐dielectric 2D structure on the silicon waveguide by shallow etching with hexagonal patterns. In the experiment, the device simultaneously converts the TE_i modes to the TE_i+3 (i = 0, 1, and 2) modes. The length of the multi‐mode converter is 16.2 µm. The TE₀–TE₃, TE₁–TE₄, and TE₂–TE₅ mode conversion processes exhibit low insertion losses (0.4 to 1.0 dB) and reasonable crosstalk values (−14.1 to −16.5 dB) at 1538 nm. The scalability of the converter is also verified by simulations.