arXiv subjects

Martin Vergara

Publications and source records attributed to Martin Vergara.

4 recordsLinked to original sources

arXiv2022

Quasi-perfect vector vortex beam multiplexing using an LCoS

In this paper we show a method for creating multiple independent quasi-perfect vector vortex beams with real-time programmable radii, topological charges, polarization orders and position in 3 dimensions, using a device based on a phase-only liquid crystal on silicon display. We achieved the simultaneous generation of up to 7 independent beams, with topological charges from -3 to 3, and found great agreement between the simulated and the measured phases and polarization structures. Additionally, we used the same scheme for enhancing the depth of focus of a single beam, resulting in a "tube" beam that preserves its properties during propagation.

physics.optics↗

arXiv2021

Generalized and multiplexed $q$-plates: experimental implementation

In this paper we generalize the concept of $q$-plate, allowing arbitrary functions of both the radial and the azimuthal variables, and study their effect on uniformly polarized beams in the near and far-field regime. This gives a tool for achieving beams with hybrid states of polarization (SoPs), and alternative phase and intensity distributions. We also implement an experimental device based on a liquid crystal on silicon (LCoS) display for emulating these generalized $q$-plates. Moreover, we propose an application that takes advantage of the pixelated nature of this kind of devices for creating arbitrary superpositions of vector and vortex beams by representing onto the LCoS randomized combinations of two different $q$-plates, i.e. multiplexed $q$-plates. Great agreement is found between theoretical and experimental results.

physics.optics↗

arXiv2019

Orbital angular momentum tuning using a phase only parallel aligned LCoS display

We propose two schemes for achieving continuous and complete orbital angular momentum tuning using a simple device based on a phase only parallel aligned liquid crystal on silicon display, where the tuning is managed by changing the input beam state of polarization. We use an optical tweezers toolbox to simulate the optical force field of the tuned beams applied to dielectric spherical particles in order to prove the applicability of the method.

physics.optics↗

arXiv2019

Generalized q-plates and novel vector beams

We generalized the conventional concept of q-plate, allowing in its definition non linear functions of the azimuthal coordinate, and simulated the resulting fields of applying this kind of element to uniformly polarized input beams, both in the near (Fresnel diffraction) and the far field (Fraunhofer diffraction) approximations. In general terms, when working in the near field regime, the chosen function defines the output polarization structure for linearly polarized input beams, and the phase of the output field for circularly polarized input beams. In the far field regime, it is obtained that when there are non-linearities in the azimuthal variable, the central singularity of the polarization field of a vector beam may bifurcate in several singularities of lower topological charge, preserving the total charge. Depending on the chosen q-plate function, different particular behaviours on the output beam are observed, which offers a whole range of possibilities for creating novel vector beams, as well as polarization critical points and singularity distributions.

physics.optics↗