Polymer Vortex Retarders VR128-532

Overview

The VR128-532 is a polymer vortex retarder that converts a Gaussian beam into an optical vortex carrying orbital angular momentum with topological charge m = 128 at a design wavelength of 532 nm. A liquid-crystal-polymer layer is sandwiched between N-BK7 window plates: the fast axis rotates continuously in the azimuthal direction while the retardance stays uniform at λ/2 across the whole aperture, so the vortex is imposed by the geometric (Pancharatnam-Berry) phase rather than by any surface-relief microstructure.

Applications

• Optical tweezers and particle manipulation
• Stimulated emission depletion (STED) microscopy
• Orbital-angular-momentum (OAM) mode generation and multiplexing
• Vortex-beam interferometry and metrology
• Laser materials processing with annular beams

Construction & Performance

The element measures Ø25.4 x 3.2 mm with a Ø21.5 mm clear aperture and is supplied in an SM1-8A Housing mount. Transmittance at the working wavelength is >97% and the conversion efficiency into the target vortex mode is ≥99.5%; the anti-reflection coating is specified as Ravg<0.5% @400-700 nm. Wavefront error is <λ/4 @633 nm, surface quality 40/20, retardance accuracy ±5 nm and fast-axis accuracy ±1°. Accepted input beam diameters run from Ø0.5 to Ø21.5 mm, with the beam centred on the singularity to better than <0.5 mm.

Storage & Handling

Operate and store between -20 to 80°C in a dry, dust-free environment. The liquid-crystal-polymer layer is sealed between glass, but the coated surfaces should still be protected from abrasion; centre the beam on the vortex singularity and keep the element capped when it is not in use.