Adaptive Spiral Diffractive Lenses—Lenses With a Twist

Abstract

An SDL results from adding the radially varying phase delay of a conventional Fresnel diffractive lens [22] with the azimuthally varying phase delay of a spiral phase plate (SPP) [23] and then perform a phase-wrapping about 2π (Figure 1a-c). A similar process has recently been presented by Guo et al. for generating axicons. [24] An alternative SDL could have been produced starting with a lens with twice the optical power and twice the topological charge (Figure 1d-f). The equation describing the constant phase spiral symmetry of this lens can be cast as

A high birefringence liquid crystal for lenses with large aperture

“…The field of LC-tunable lenses is very active at the moment 25 , 26 , as they can be used in ophthalmic applications 27 – 29 , mobile phones 30 , autostereoscopic devices 31 , 32 , plenoptic capture systems 33 , 34 , virtual reality displays 35 , to name some key enabled applications. In recent years, numerous structures have been proposed, e.g., by using curved electrodes 36 , 37 , built-in dielectric layers 38 – 40 , multielectrodes 41 – 44 and modal lenses 27 , 30 , 45 , 46 . Some disadvantages of curved electrodes and dielectric layers are the high required voltages due to the distance of the electrode to the LC layer.…”

Widely tunable large area thin liquid crystals lens

“…Lenses were manufactured and characterized optically as previously described 14,17 . The electrodes of the two identical 25 mm diameter lenses with 24 electrodes were designed so that each of the lenses had a focal length of 12 meter for topology 1.…”

“…A discrete SDLs are the combination of the radial symmetry of a discrete diffractive Fresnel lens and the azimuthal symmetry of discrete SPPs, leading to a spiral symmetry 15 , inheriting the singularity and the OAM from the SPP, and the focusing aspects of the lens. In collaboration with the groups of Prof.s Moreno and Davis we were the first to develop specific tunable liquid crystal SDLs 16 , and their subsequent use as imaging lenses 17 . In this latter study we presented, how the SPP character of the SDL could be eliminated by cascading an SDL with a SPP with opposite hand, leading to the twist free emulation of a tunable Fresnel lens.…”

Active Optical Beam Shaping Based on Liquid Crystals and Polymer Micro-Structures

“…This is achieved by using small electrodes with narrow spacing. Often, very complex or even multi-layered electrodes and LC structures are used [27][28][29][30]. To simplify the device structure and limit the complexity of driving electronics, resistive or dielectric layers are sometimes deposited in-between the addressing electrodes to smoothen the potential distribution [31][32][33][34].…”