Dilson P. Caetano

Hermite-Bessel beams and the geometrical representation of nondiffracting beams with orbital angular momentum.

We investigate theoretically and experimentally the decomposition of high-order Bessel beams in terms of a new family of nondiffracting beams, referred as Hermite-Bessel beams, which are solutions of the Helmholtz equation in Cartesian coordinates. Based on this decomposition we develop a geometrical representation of first-order Bessel beams, equivalent to the Poincaré sphere for the polarization states of light and implement an unitary transformation within our geometrical representation using linear optical elements.

Oblique interaction of spatial dark-soliton stripes in nonlocal media

We report what we believe to be the first experimental observation of a large spatial lateral shift in the interaction of obliquely oriented spatial dark-soliton stripes. We demonstrate by numerical simulations that this new effect can be attributed to the specific features of optical media with a nonlocal nonlinear response.

Effects of pseudothermal light source's transverse size and coherence width in ghost-interference experiments.

Ghost interference is experimentally investigated by varying the pseudothermal light sources transverse size and coherence width. Our results show that by increasing the transverse size of the source the quality of the interference pattern is improved, while the visibility is reduced. On the other hand, by increasing the coherence width of the source, the visibility of the interference pattern is improved, while the quality is reduced. These experimental results corroborate previous theoretical results.

The effect of disorder on two-dimensional photonic crystal waveguides

We investigate the effect of positional disorder on two-dimensional photonic crystal waveguides created by removing a line of cells from a finite 11×11 square lattice. By using transverse magnetic and transverse electric waves, we have studied three different configurations: disorder throughout the whole crystal, disorder only in the waveguide border, and disorder in the whole crystal except the waveguide border. We found that the waveguide performance is quite robust against disorder in the case where the waveguide border is not affected by disorder. In the other cases, disorder changes the size of the waveguide channel, which has a detrimental effect on the performance of the waveguide.

Observation of interference pattern in the intensity correlation of a non-local object using a Hanbury Brown and Twiss-type experiment

We report on the experimental observation of interference pattern of a distributed double-slit, consisting of a single-slit and a wire spatially separated, illuminated by two beams from a pseudothermal light source, in Hanbury Brown and Twiss–like configuration. The interference pattern is obtained performing a classical correlation with the intensities of the light beams scattered by each part of the double-slit. A theoretical analysis confirms our experimental results, showing that classical correlations can also mimic non-local properties analogue to those using twin photons for quantum images.

Observation of spatial shift in interaction of dark nonlocal solitons

We study experimentally and theoretically a two- dimensional interaction of dark solitons in thermal defocusing medium. We report on the experimental observation of a spatial shift occurring at the intersection of obliquely interacting dark solitons. Numerical modeling reveals that this new effect is due to the nonlocal character of thermal nonlinearity.

Pulses with Non Analytical Points Described by Functions with Compact Support: The Information Velocity in a Fast-Light Medium

A new approach to associate information to non analytical points of optical pulses is investigated. These pulses propagation through a dispersive medium is numerically studied and the information velocity is characterized for superluminal propagation.

Direct determination of light beams’ topological charges using diffraction

We demonstrate a new method to measure the phase singularity of light beams with orbital angular momentum, based on the diffraction by a triangular aperture. We have applied our method to Bessel and Laguerre-Gauss beams.

Fast Light, Non-Analytical Points and the Speed of Information Using Pulses Described by Functions with Compact Support

We compare the propagation of pulses based on gaussian analytical functions and on functions with compact support, that present perfectly smooth non analytical points, to clarify the relation between not analytical points and information.

Triangular slit interference pattern of single photons with orbital angular momentum: Another beautiful experiment?

The Young double slit experiment with single quantum particles (electrons or photons) has been quoted as the most beautiful experiment in physics [1]. Among the reasons given for this is that it shows the wave-particle duality of light and is a nice demonstration of quantum physics. Another very important quantum feature of light that has attracted a lot of attention in recent years is the fact that it can contain orbital angular momentum (OAM) besides spin angular momentum. It has been demonstrated that Laguerre-Gaussian beams which have optical vortices with a topological charge m carry a well-defined OAM equals to mh per photon [2].