Geometric definition of the V-parameter in photonic crystal fibers

Abstract

We propose a general geometric definition of the V-parameter in photonic crystal fibers (PCF). We argue that the fundamental modal field in both square-lattice and triangular-lattice PCFs can be approached by certain proper assemblies of the fundamental mode in a one-dimensional planar waveguide. This observation suggests a geometric definition of the effective core radius and the single-mode regime of V≤π/2 in various PCFs. The numerical results imply that the suggestion is valid for all of the one-rod, seven-rod, 19-rod, and 37-rod core triangular-lattice PCFs and the one-rod, nine-rod, and 25-rod core square-lattice PCFs.