Polarization singularities in the two-mode optical fiber output

We report here the controlled generation of polarization singularities (PS) in the output beam from a two-mode optical fiber, obtained via coherent superposition of the fundamental (HE11) mode with the vortex (CV +/- 1 +/-/IV +/- 1 +/-) modes by selectively coupling circularly polarized (sigma = +/- 1) Gaussian (TEM00) input beam at two different launch angles. The PS in the output beam are characterized using the complex Stokes fields and interferometry measurements, based on the two-mode optical fiber which are an effective means to generate, manipulate, study, and use isolated PS, depending strongly on the input launch conditions. (C) 2011 Optical Society of America