RESUMO
In this paper we compare the intensity distributions in the paraxial and tightly focused regimes corresponding to a double ring perfect optical vortex (DR-POV). Using the scalar diffraction theory and the Richards-Wolf formalism, the fields in the back focal plane of a low and high (tight focusing) NA lens are calculated. In the paraxial case we experimentally observed a DR-POV whose rings enclose a dark zone thanks to the destructive interference introduced by a π phase shift. In the tightly focused regime, however, the numerical simulations showed that the intensity near the focus is influenced by the input field polarization and it is not intuitive. In both cases we found that the dark region subtended between the rings has a minimal width that is inversely proportional to the pupil radius of the system, reaching 0.42λ for the radially polarized DR-POV. For the tightly focused case, we calculated the optical forces in the transversal and longitudinal coordinates exerted on a metallic particle. As a result, it is theoretically demonstrated that the circularly polarized DR-POV can trap Au metallic particles in 3D using a light wavelength close to its resonance.
RESUMO
The study of light propagation though the atmosphere is crucial in different areas such as astronomy, free-space communications, remote sensing, etc. Since outdoors experiments are expensive and difficult to reproduce it is important to develop realistic numerical and experimental simulations. It has been demonstrated that spatial light modulators (SLMs) are well-suited for simulating different turbulent conditions in the laboratory. Here, we present a programmable experimental setup based on liquid crystal SLMs for simulation and analysis of the beam propagation through weak turbulent atmosphere. The simulator allows changing the propagation distances and atmospheric conditions without the need of moving optical elements. Its performance is tested for Gaussian and vortex beams.
