LAUSR

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 TE₀ to TE₂ mode can be realized within an ultracompact size ( $\sim 7.66~\mu \text{m}$ ) by designing the arrow-like slot structure. With the help of asymmetric directional coupler (ADC), the TE₀-to-TE₂ 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 TE₀-to-TE₁ 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.