arXiv subjects

Alberto Lencina

Publications and source records attributed to Alberto Lencina.

4 recordsLinked to original sources

arXiv2019

Description of a multifocal arrangement of asymmetric Kummer-beam optical vortices

In this work, an analytic expression is derived for the optical field generated by an off-axis Gaussian beam diffracted by a Discrete Vortex-Producing Lens. With this system, a multifocal arrangement of asymmetric optical vortices is obtained whose topological charge values change with the position along the optical axis. This scheme allows obtaining a principal asymmetric vortex corresponding with the topological charge value of the phase mask and secondary ones with different charges. With the analytical expression, the effects induced by the discretization and misalignment on the irradiance and phase of each vortex can be simultaneously studied. A signal-to-noise ratio expression is derived to verify if the noise of the multifocal system might affect importantly the optical vortices of interest. Finally, we proposed new metrics to measure the off-axis displacement using the phase of the vortex. We concluded that noise is not a problem, then a Discrete Vortex-Producing Lens can be used as a continuous Spiral Phase Plate with the bonus that secondary optical vortices can be used in the same way as principal optical vortices.

physics.optics↗

arXiv2017

Analytical description of optical vortex beams generated by discretized vortex producing lenses

Discretized vortex-producing lenses programmed on low performance spatial light modulators have been used for the generation of optical vortices. However, the description of these vortices has been supported only by numerical simulations. In this work, a general analytical treatment (any topological charge - any discretization levels) for the propagation of a Gaussian beam through a discretized vortex-producing lens is presented. The resulting field could be expressed as a sum of Kummer beams with different amplitudes and topological charges focalized at different planes, whose characteristics of formation can be modified by tuning the parameters of the setup. Likewise, vortex lines are analyzed to understand the mechanism of formation of observed topological charges, which appear in specific planes. Conservation of the topological charge is demonstrated. Theoretical predictions are supported by experiments.

physics.optics↗

arXiv2006

Alternative method for wave propagation analysis within bounded linear media: conceptual and practical implications

This paper uses an alternative approach to study the monochromatic plane wave propagation within dielectric and conductor linear media of plane-parallel-faces. This approach introduces the time-averaged Poynting vector modulus as field variable. The conceptual implications of this formalism are that the nonequivalence between the time-averaged Poynting vector and the squared-field amplitude modulus is naturally manifested as a consequence of interface effects. Also, two practical implications are considered: first, the exact transmittance is compared with that given by the Beer's Law, employed commonly in experiments. The departure among them can be significative for certain material parameter values. Second, when the exact reflectance is studied for negative permittivity slabs, it is show that the high reflectance can be diminished if a small amount of absorption is present.

physics.gen-ph↗

arXiv2005

Squared-field amplitude modulus and radiation intensity nonequivalence within nonlinear slabs

This paper presents a novel approach to wave propagation inside the Fabry-Perot framework. It states that the time-averaged Poynting vector modulus could be nonequivalent with the squared-field amplitude modulus. This fact permits the introduction of a new kind of nonlinear medium whose nonlinearity is proportional to the time-averaged Poynting vector modulus. Its transmittance is calculated and found to differ with that obtained for the Kerr medium, whose nonlinearity is proportional to the squared-field amplitude modulus. The latter emphasizes the nonequivalence of these magnitudes. A space-time symmetry analysis shows that the Poynting nonlinearity should be only possible in noncentrosymmetric materials.

physics.optics↗