Segmented cladding index guiding photonic crystal fiber

In this paper a segmented photonic crystal fiber with segments of varying effective refractive index in the cladding has been proposed. The designs have been analyzed in view of the effect of change in their cladding parameters, such as refractive index contrast, air filling fraction (denoted by normalized air hole diameter), duty cycle of the segments, and core-cladding interface. The periodically varying high and low index regions have been created by considering variations in the air hole size. High index core region has been created by omitting a single air hole from the centre of the lattice. Phosphate glass (n=1.56) has been used as base material. The various designs obtained by varying the controlling parameters, have been investigated for properties such as the effective core and cladding indices, confinement of fundamental mode and higher order mode, and the V parameter values. These parameters have been investigated over near infrared (0.75 -1.4 μm) to short wavelength infrared (1.4-2.3 μm) spectral range using finite difference time domain method. The expression for V parameter for conventional photonic crystal fiber has been extended to the proposed design and single mode cutoff value for the design has been calculated. The proposed design offers robust single mode confinement over specified infrared (0.75-2.3 μm) wavelength range and a broad confinement peak has been observed containing the third optical communication window at 1.55 μm.