Flat variable liquid crystal diffractive spiral axicon enabling perfect vortex beams generation

Abstract

A transparent variable diffractive spiral axicon (DSA) based on a single LC cell is presented. The manufactured DSA can be switched between 24 different configurations, 12 convergent and 12 divergent, where the output angle is varied as a function of the applied topological charge. The active area of the device is created using a direct laser writing technique in indium-tin oxide coated glass substrates. Liquid crystal is used to modulate the phase of the incoming beam generating the different DSA configurations. The DSA consists in 24 individually driven transparent spiral shaped electrodes, each introducing a specific phase retardation. In this article, the manufacture and characterization of the tunable DSA is presented and the performance of the DSA is experimentally demonstrated and compared to the corresponding simulations.

Easy manufacture large aperture wide range variafocal liquid crystal diffractive lens

“…Discretizing resulting phase map into a finite number of phase delays (in our case 24 or 72), leads to 24 or 72 angularly equal-spaced spiraling pixels, separated by lines that in the case of a Cartesian Oval lens are practically Fermat´s spirals (Figure 2). In the case of an axicon shaped lens the spirals would have been Archimedean 22 .…”

Optimizing Tunable LC Devices with Twisted Light

“…Axicons are closely related to vortices, which are commented on in the next section. Diffractive spiral axicons (DSA) have been recently proposed [55] for the generation of Perfect Vortex Beams (PVB).…”

Reconfigurable perfect vortex beam generator based on a liquid crystal spiral phase plate

“…The developed electronic driver generates 72 independent 12-bit Pulse Width Modulation (PWM) outputs, determining the phase delay imposed to each pixel and therefore controlling the light beam TC. The PWM signal modulates a square 5Vpp, 1kHz signal generating the desired RMS voltage applied to apply to each pixel [17].…”

“…In 2013 Ostrovsky et al proposed the perfect vortex beam (PVB) concept to avoid this dependence between the intensity pattern radius and the TC [16]. Thus, PVBs are light beams characterized by carrying different OAMs without modifying their intensity ring pattern radius [17].…”