A comparative study of high birefringence and low confinement loss photonic crystal fiber employing elliptical air holes in fiber cladding with tetragonal lattice

We numerically compare the mode birefringence and confinement loss with four patterns (case A-D) of index-guiding photonic crystal fibers (PCF) using the finite element method. These PCFs are composed of a solid silica core surrounded by different sizes of elliptical air holes and a cladding which consist of the same elliptical air holes in fiber cladding with tetragonal lattice. The maximal modal birefringence and lowest confinement loss of our proposed case A structure at the excitation wavelength of λ = 1550nm can be achieved at a magnitude of 5:3 × 10^-2 (which is the highest value to our knowledge) and less than 0.051 dB/km (an acceptable value less than 0.1 dB/km) with only four rings of air holes in fiber cladding, respectively. The merit of our designed PCFs is that the birefringence and confinement loss can be easily controlled by turning the pitch (hole to hole spacing) of elliptical air holes in PCF cladding.