Design of zeonex based polarization maintaining low loss porous core fiber for terahertz regime

Abstract

We present two novel Zeonex based single-mode ultra-high birefringent porous core micro-structured fibers, one consisting of slotted cladding with hybrid core and another consisting of elliptical shaped suspended core for THz wave guidance. Full-vector finite element method with perfectly matched layer boundary condition is used to investigate the wave guiding property including single mode operation, birefringence, effective material loss, confinement loss, core power fraction, dispersion, modal effective area and fiber nonlinearity of both fibers. Addition of four circular air holes along with only three elliptical air holes in the core of the proposed model 1 enhances the value of birefringence to 0.0818 with an effective material loss of only 0.0448 cm-1 and a confinement loss of 4×10-7 cm-1 at an operating frequency of 1 THz. Moreover, its compact slotted geometry in the cladding imposes as high as 55.3% of total modal power to flow through the core air holes. Furthermore, a near flattened dispersion of 1.196±0.08 ps/THz/cm for a broad frequency range (0.9-1.6THz) and fiber nonlinearity of 3.33×10-9 W-1m-1 for an effective area of 1.32×105 µm2 are obtained for x-polarized mode for the same operating frequency. On the other hand, model 2 at optimum design parameters shows an ultra high birefringence of 0.1116 which is the highest so far to the best of our knowledge, lower absorption loss of 0.04716 cm-1, a negligible confinement loss of 2.65×10-7cm-1 and a low flat dispersion flattened characteristics over a wide terahertz band. Furthermore, the proposed model 2 allows a significant amount of total power to flow through the core air-slots. Moreover, due to its larger effective area, the proposed PCF demonstrates negligible non-linearity. A latest cyclo-olefin polymer (COP) based material, trade name Zeonex, is chosen as the background material for both of our proposed model because of its unique advantages over other materials. Moreover, it has lower specific gravity, chemical resistance at elevated temperature, higher transparency, lower melt flow index etc. Furthermore, the physical properties of Zeonex are also suitable for high quality fiber drawing. Also, fluctuations in the fiber diameter are reduced because of the greater stability of drawing process. The proposed fibers can easily be fabricated using extrusion technology and would be suitable for polarization maintaining applications with a minimal absorption loss in the terahertz regime.