  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, 4x4
and 6x6 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 4x4 and 6x6 intersections based on
GPC-MFE lens, crosstalk levels are below -24dB and -18dB, and the average
insertion losses are 0.60dB and 0.85dB in the C-band with lenses' radii of 7xa
and 10xa, respectively, where a is the lattice constant of the photonic
crystal.
