Fig. 4: Experimental results of high-order mode operators.

a Displayed from left to right are the SEM image of a fabricated TE₀-TE₅ mode operator (left), the measured mode conversion efficiency when the input is the TE₀ mode (middle), and the TE₅ mode (right). b Similar results corresponding to the TE₀-TE₁₀ mode operator. c Microscope pictures of the fabricated PIC consisting of a mode spot size converter, multiple cascaded B2B mode operators, and a high-order mode filter. d, e SEM images for the zoom-in view of two B2B high-order mode operators. f, g Measured transmission spectra for six cascaded B2B TE₀-TE₁₉ and TE₀-TE₂₀ mode operators, respectively. h The total ELs are linearly dependent on the device number