  Intersection of two or more silicon slot waveguides is inevitable in modern
optical integrated circuits based on silicon on insulator (SOI) platform. In
this article, we design a Maxwell's fisheye lens as the crossing medium for
three Si slot waveguides and numerically investigate its characteristics such
as insertion loss, crosstalk and bandwidth. For the 3$\times$3 slot waveguide
crossing, the average insertion loss of 1.2 dB and crosstalk levels lower than
-15.1 dB are achieved in an ultra-wideband wavelength range of 415 nm covering
the entire O, E, S, C, L, and U bands of optical communications. The footprint
of the 3$\times$3 silicon slot waveguide crossing presented in this article is
merely 2$\times$2 $\mu m^2$ which is considerably smaller compared to the
previously designed Si slot waveguide crossings even with fewer number of
ports. The proposed design can be expanded to support the intersection of more
slot waveguides.
