We have generated a vortex beam with spiral polarization using a few-mode optical fiber. The excitation of the beam is controlled by coupling conditions of incident light beam with the fiber and the state of polarization of input Gaussian beam. The constituent orthogonal linearly polarized modes that contribute to the generation of such spiral vortex beam by inherent mode-mixing are also selectively excited by launching orthogonally polarized light into the fiber input end. Our experimental results suggests a strong dependency of polarization and phase of the fiber output beam on the state of polarization of input beam and are expected to be useful in mode conversion and controlled OAM beam generation. The obtained experimental results are best matched with simulation results.
Photonic bandgap of two dimensional semiconductor photonic crystal structures of square and triangular lattices are
studied using plane wave expansion method. The bandgap and dispersions also studied by introducing point and line
defect in that structure. Hence a comparative study has been presented among the various structures.