Spatially-variable retardation plate for efficient generation of radially- and azimuthally-polarized beams

We investigate conversion of a linearly-polarized Gaussian beam to a radially- or an azimuthally-polarized doughnut (0, 1)* Laguerre-Gaussian (LG) beams, performed with a spatially-variable retardation (SVR) plate. The SVR plate is composed of eight sectors of a lambda/2 retardation plate, each one with different orientation of the to crystal's stow axis. The analysis reveal that nearly-pure radially- or azimuthally-polarized LG(01)* beam with M-2 = 2.2 can be obtained, while the transformation efficiency is 89.6%. In the experiments, performed with Nd:YAG laser, we transformed a Gaussian beam with M-2 = 1.3 to a radially- and azimuthally-polarized (0, 1)* Laguerre-Gaussian beams with M-2 = 2.5. We carefully characterized the polarization state of the obtained radially- and azimuthally-polarized beams, measuring Stokes parameters. The polarization purity of the obtained beams, calculated from the measured data, was as high as 96%. (c) 2007 Elsevier B.V. All rights reserved.