Experimental Demonstration of Compact Mode Converter Based on Conformal Dielectric Metasurface

In this letter, we designed and experimentally demonstrated a compact mode converter in silicon-on-insulator (SOI) waveguide based on conformal dielectric metasurface, which uses polygonal slot structure to manipulate the wavefront of guided modes. Mode conversion from TE
₀
to TE
₂
mode can be realized within an ultracompact size (~7.66 μm) by designing the arrow-like slot structure. With the help of asymmetric directional coupler (ADC), the TE
₀
-to-TE
₂
mode converter was measured in the experiment with low insertion loss (IL) (<; 0.5 dB) and low crosstalk (CT) (<; -8.0 dB) from 1525 to 1565 nm. Moreover, a TE
₀
-to-TE
₁
mode converter using another polygonal slot structure was also experimentally demonstrated. Our proposed mode converter shows great potential in high-density integration of photonic devices for on-chip mode control.