Changes of propagation characteristics with core parameters in kagome-structured hollow-core photonic crystal fibers

Based on all-vector finite element method, general features of the loss spectrum of large-pitch kagome lattice hollow-core photonic crystal fiber(HC-PCF) are exhibited by investigating the effects of the core size, core shape and core-cladding boundary width on the guidance properties of the fiber. The numerical simulations show that the operational bandwidth of the fiber is drastically affected by improper core design parameters which cause the interaction among the fundamental core modes, surface modes and cladding modes. Therefore, the design of large-pitch kagome lattice HC-PCF with low loss and broad bandwidth should satisfy these conditions: the core size maintains the complete micro-structures of the cladding, the core shape matches the micro-structure of the cladding cells, and the