Generation of few µm high optical vortex using tunable spiral plates

Abstract

Optical vortices have been extensively explored, due to its widespread applications, spanning from optical trapping to laser processing. Previously, several ways for generating optical vortices had been reported. However, none of the previously reported methods demonstrated the design of a geometrically variable tunable spiral plate capable of tuning the optical vortex's features. In this study, we present a three-dimensional tunable spiral plate capable of generating desired vortex and focal characteristics. These spiral plates are 10 µm in width and 7-17 µm in height, generating few µm high vortices. We used the 3D FDTD approach to model and simulate these spiral plates for incident plane waves with a wavelength of 632 nm. We show that the vortex profiles can be tweaked in two ways: by changing the spiral plate's geometrical features along the vertical axis, and by changing its refractive index.