Ultrasmall radial polarizer array based on patterned plasmonic nanoslits

We developed an ultrasmall radial or azimuthal polarization converter of size ranged from 10 to 100 μm. The converter consists of a half-wave plate divided into four quadrants, each of which is made of periodic gold nanoslits at different orientations in steps of 45°. The converter and its array were fabricated and followed by an evaluation with the Sénarmont method and the polarization microscopy. Due to the giant birefringence of the gold nanoslits, each slit segment achieved 180° retardation at the wavelength of 633 nm, and the conversion from linear to radial polarization was demonstrated.