Modes in Air-core Bragg Fibers

Abstract

The modes supported in air-core Bragg fibers are modeled and simulated by using a full-vectorial 1-Dimensional finite-difference frequency-domain method (FDFD). A perfectly matched layer (PML) terminated by a zero boundary condition is applied as numerical absorption boundary condition such that with proper PML parameters, three types of modes are well defined and divided into branches in the mode spectrum. The three types of modes can be identified as quasi-guided modes, mainly depending on Bragg fiber properties; leaky modes, having tricky relationship with the parameters of both Bragg fiber and PML; and PML modes, mainly depending on the parameters of PML.