Analysis of Hybrid Vector Beams Generated with a Detuned Q-Plate

Abstract

We use a tunable commercial liquid-crystal device tuned to a quarter-wave retardance to study the generation and dynamics of different types of hybrid vector beams. The standard situation where the q-plate is illuminated by a Gaussian beam is compared with other cases where the input beam is a vortex or a pure vector beam. As a result, standard hybrid vector beams but also petal-like hybrid vector beams are generated. These beams are analyzed in the near field and compared with the far field distribution, where their hybrid nature is observed as a transformation of the intensity and polarization patterns. Analytical calculations and numerical results confirm the experiments. We include an approach that provides an intuitive physical explanation of the polarization patterns in terms of mode superpositions and their transformation upon propagation based on their different Gouy phase. The tunable q-plate device presents worthy advantages, since it allows a compact and efficient generation of pure and hybrid vector beams to study these effects.

Superposition of vortex beams generated by polarization conversion in uniaxial crystals

“…One of the most intriguing phenomena that have been observed for the linearly polarized Laguerre–Gauss beam incident on the optical system is the breaking of the circular symmetry as the beam propagates to the lens’s focal plane. This behaviour is theoretically explained in one of our previous work 31 as well as in Quiceno-Moreno et al 21 to be caused by the Gouy phase shift associated with the propagation of Laguerre–Gauss modes to the focal plane of a lens.…”

“…The approaches using combinations of diffractive or geometrical optical elements are much simpler and more efficient 19 , 20 . Quiceno-Moreno et al 21 used two q-plates placed in line, one having tunable retardance, for the generation and the investigation of HVBs in both near and far-field.…”

Polarization state generator for the generation of complex light with controllable degree of polarization

“…The beam emerging from the PSG is spatially filtered and collimated, and it then illuminates a liquid-crystal tunable qplate of from ArcOptix [15] with its retardance set to radians. Hence, a vector beam with maximum polarization conversion efficiency is produced at the output.…”

Vector beams generated with a Fourier transform processor with geometric phase grating

“…For arbitrary values of the charges, the so-called hybrid vector beams are generated. 4,5 Here we concentrate on an earlier approach to generate vector beams, which is based on a classical Fourier transform 4f processor. [6][7][8] This system employs a diffraction grating to split the incoming beam, using a polarization filter at the Fourier plane that uses two discrete quarter-wave plates (QWPs) to filter the ±1 diffraction orders and transform their polarization states.…”

“…In both cases, the effective generation of pure vector beams implies the collinear superposition of a circular right (RCP) and a left (LCP) polarization light vortex beam, each carrying azimuthal phases with opposite topological charge ℓR=−ℓL. For arbitrary values of the charges, the so-called hybrid vector beams are generated 4 , 5 …”