Bending resistive improved effective mode area fluorine doped quadrilateral shaped core photonic crystal fiber for high power fiber lasers

In this paper we propose a new design of a low loss large mode area (LMA) quadrilateral core photonic crystal fiber (QC-PCF). Removal of air holes from the rings adjacent to core and insertion of lower index rod near core region enables the fiber to enhance effective mode area even in bent condition. Finite element method (FEM) based software is used to simulate and analyze the guiding properties. According to simulation effective mode area of 1798 μm2 is achieved at an operating wavelength of 1.064 μm when no lower index rod is used. At the same time, the fiber provides ultra-low confinement loss of 9.38 × 10−13 dB/m. The area of our PCF reduces to 989 μm2 when it is bent at a radius of 30 cm with low bending loss of order 1.95 × 10−5 dB/m. On the other hand, the shrinkage of mode area due to bending is reduced from 45% to 36% by employing low index fluorine doped rods around the core. Moreover, both confinement loss and bending loss reduce significantly to 3.05 × 10−16 dB/m and 1 × 10−6 dB/m respectively. However, our proposed quadrilateral shaped core PCF can be a consistent competitor in realm of high power lasers.