Highly birefringent photonic crystal fiber with squeezed hexagonal and rectangular lattices

The birefringence of photonic crystal fiber (PCF) with squeezed hexagonal and rectangular lattices was calculated by a finite element software. Squeezes in the x and y directions were taken into account considering an elliptical microstructure of holes. High values for the birefringence could be reached: 2.0/spl times/10/sup -2/ and 7.5/spl times/10/sup -3/ for hexagonal and rectangular lattices, respectively.