EFFICIENT RADIALLY POLARIZED LASER-BEAM GENERATION WITH A DOUBLE INTERFEROMETER

Conversion of a linearly polarized CO2 laser beam into a radially polarized beam is demonstrated with a novel double-interferometer system. The first Mach-Zehnder interferometer converts the linearly polarized input beam into two beams With sin2 theta and cos2 theta intensity profiles, where theta is the azimuthal angle. This is accomplished by using two spiral-phase-delay plates with opposite handedness in the two legs of the interferometer to impart a one-wave phase delay azimuthally across the face of the beams. After these beams are interfered with, the resulting beams are sent directly into the second Mach-Zehnder interferometer, where the polarization direction of one beam is rotated by 90-degrees. The beams are then recombined at the output of the second interferometer with a polarization-sensitive beam splitter to generate a radially polarized beam. The output beam is almost-equal-to 92% radially polarized and contains almost-equal-to 85% of the input power. This system will be used in upcoming laser particle acceleration experiments.