Optical Properties of Photonic Crystal Fibers with a Fiber Core of Arrays of Sub- Wavelength Circular Air Holes: Birefrin- Gence and Dispersion

We propose a kind of novel photonic crystal fibers (PCFs) based on a fiber core with arrays of subwavelength circular air holes, achieving the flexible control of the birefringence or the dispersion property of the PCFs. A highly birefringent (HB) PCF is achieved by employing arrays of subwavelength circular air hole pairs in the fiber core, which are arranged as a conventional hexagonal lattice structure with a subwavelength lattice constant. The HB-PCF is with uniform and ultrahigh birefringence (up to the order of 0.01) in a wavelength region from 1.25μm to 1.75μm or even a larger region, which, to the best of our knowledge, is the best birefringence property of the PCFs. A dispersion-flattened (DF) PCF with near-zero dispersion is achieved by employing arrays of subwavelength circular air holes in the fiber core arranged as a conventional hexagonal lattice structure with a subwavelength lattice constant, which contributes negative waveguide dispersion to the PCF. The proposed design of the DF-PCF provides an alternate approach for the dispersion control of the PCF. Besides the high birefringence and the flattened near-zero dispersion, the proposed PCFs with a fiber core of arrays of subwavelength circular air holes have the potential to achieve a large mode area single mode PCF. Corresponding author: D. Chen ([email protected]). † Also with Photonics Research Centre, Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China. 194 Chen, Tse, and Tam