Formation of optical vortices with topological charge |l|=1 and |l|=1/2 by use of the S-waveplate

We theoretically and experimentally demonstrate the generation of optical vortices using an S-waveplate, fabricated by femtosecond laser writing in silica glass. It is shown that this method allows to form orthogonally polarized vortices with fractional topological charge. At the double wavelength of the S-waveplate, the superposition of orthogonally polarized optical vortices with topological charge l=1/2 was generated. After separating the resulting beam with polarizer, optical vortices of topological charge l=1/2 were obtained. Vortices of fractional topological charge were detected by interfering the vortex beam with a Gaussian beam. A slightly laterally misadjusted Michelson interferometer was used for detection of vortices with integer topological charge.