Highly Birefringent Elliptical-Hole Photonic Crystal Fiber With Two Big Circular Air Holes Adjacent to the Core

In this letter, we propose a novel design for a polarization -maintaining index-guiding photonic crystal fiber (PCF). It is composed of a solid silica core, two big circular air holes near the core, and a cladding with elliptical air holes. Using a full-vector finite-element method, we study the modal birefringence of the fundamental mode in such a PCF. The numerical result shows that very high modal birefringence with magnitude of order of $10^{ - 3}$ has been obtained, which are higher than the birefringence induced by adding two big air holes near the core or using elliptical air holes in cladding separately.