Highly birefringent index-guiding photonic crystal fibers

Photonic crystal fibers (PCFs) offer new possibilities of realizing highly birefringent fibers due to a higher intrinsic index contrast compared to co nventional fibers. In this Letter, we analyze theoretically the levels of b irefringence that can be expected using relatively simple PCF designs. Whil e extremely high degrees of birefringence may be obtained for the fibers, w e demonstrate that careful design with respect to multimode behavior must b e performed. We further discuss the cutoff properties of birefringent PCFs and present experimental results in agreement with theoretical predictions on both single- and multimode behavior and on levels of birefringence.