Photonic crystal waveguide intersection design based on Maxwell's fish-eye lens

The number of waveguides crossing an intersection increases with the development of complex photonic integrated circuits. Numerical simulations are presented to demonstrate that Maxwell's fish-eye (MFE) lens can be used as a multiband crossing medium. In previous designs of waveguide intersection, bends are needed before and after the intersection to adjust the crossing angle resulting in a larger footprint. The presented design incorporates the waveguide bends into the intersection which saves footprint. In this paper, 4 × 4 and 6 × 6 intersections based on ideal and graded photonic crystal (GPC) MFE lenses are investigated, where 4 and 6 waveguides intersect, respectively. The intersection based on ideal MFE lens partially covers the O, E, S, C, L, and U bands of optical communication, while the intersection based on GPC-MFE lens is optimized to cover the entire C-band. For 4 × 4 and 6 × 6 intersections based on GPC-MFE lens, crosstalk levels are below -24 dB and -18 dB, and the average insertion losses are 0.60 dB and 0.85 dB in the C-band with lenses' radii of 7×a and 10×a, respectively, where a is the lattice constant of the photonic crystal.