Jandir M. Hickmann

Femtosecond nonlinear optical properties of tellurite glasses

The third-order nonlinear optical properties of tellurite glasses with different compositions were investigated in the femtosecond regime at 810nm. Using the I-scan technique, positive nonlinear refractive indices of ∼10−15cm2∕W were measured. The authors also determined that nonlinear absorption was negligible for all studied samples. This result, added to their good chemical stability, indicates that tellurite glasses are promising materials for ultrafast photonic applications.

Interference of traveling nondiffracting beams

We study numerically the interference resulting from the superposition of two Bessel beams propagating in free space. We discuss how to obtain such beams and show the existence of the self-imaging effect during propagation. The evolution of the superimposed Bessel beams is analyzed on the basis of the evolution of the individual beams. Our exact numerical predictions contradict previous approximated analytical treatments, showing that they can lead to quantitatively wrong results and misleading conclusions.

Nonlinear optical properties of Au nanoparticles colloidal system: Local and nonlocal responses

Z-scan revealed thermal and electronic contributions for the nonlinear refractive index of highly stable colloid containing different concentrations of gold nanoparticles. Large enhancement factors were observed for values of n2 and dn∕dT of the colloid, due to the presence of the nanoparticles. Our results suggest that thermal effects will play an important role in the development of photonic applications involving nanostructured materials and in the investigation of nonlocal nonlinear phenomena.

Experimental observation of interfering Bessel beams.

We experimentally verified the interference resulting of the superposition of two Bessel beams propagating in free space and showed for first time the self imaging effect using nondiffracting beams. Our results are supported by numerical simulations and possible applications are discussed.

Experimental demonstration of novel effects on the far-field diffraction patterns of a Gaussian beam in a Kerr medium

We report on the experimental observation of the effects on the far-field patterns obtained when a divergent or convergent beam interacts with a thin self-defocusing material. The measurements were performed using a CW laser beam propagated through a cell containing a colloidal system that presents a very large nonlinear refractive index. The high nonlinearity of the colloid allowed for the observation of patterns never investigated before, revealing a quite different behaviour on the far field from a convergent or a divergent beam due to the opposite interaction with the negative Kerr nonlinearity of the medium. An unpredicted relation between the number of generated rings and the nonlinear phase-shift is obtained in the case of a convergent beam. Our results are in good agreement with a model for thin nonlinear media.

Nonlocal optical nonlinearity of ionic liquids

The nonlinear optical properties of two ionic liquids, 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMI]BF4) and 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMI]PF6), have been investigated using the Z-scan technique. These compounds are liquid at room temperature and present a strong ionic nature. Nonlinear refraction and absorption, and thermo-optical measurements for both ionic liquids were performed using two different laser wavelengths, 514 nm and 810 nm, in the continuous wave and femtosecond regimes, respectively. It was observed that those specimens have large negative nonlinear refractive indexes and thermo-optical coefficients, but nonlinear absorption was not observed. Different dispersion relations were observed depending on the ionic liquid anion, which may be related to the distinct structures of these compounds. This result indicates that ionic liquids are suitable media for the investigation of nonlocal nonlinear phenomena.

Fraunhofer diffraction of light with orbital angular momentum by a slit

We study the Fraunhofer diffraction problem while taking into account the orbital angular momentum of light. In this case, the phase singularity of the light beam is incident on the slit in two different cases: in one, it is incident slightly above the slit, and in the other it is centered on the slit. We observed that the symmetry and the fringe formation in the interference pattern strongly depend on the amount of orbital angular momentum and the slit position in relation to the beam.

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.

Photonic crystal based polarization control devices

It has recently been shown that the polarization of electromagnetic radiation can be completely controlled using devices constructed entirely from photonic crystals. We will review these important developments, focusing on effects that occur for propagation in the periodic plane of two-dimensional, dielectric structures. Specifically, we survey the recent experimental results demonstrating waveplates and polarizers based on two-dimensional photonic crystals.

Third-order nonlinear optical response of colloidal gold nanoparticles prepared by sputtering deposition

The nonlinear optical responses of gold nanoparticles dispersed in castor oil produced by sputtering deposition were investigated, using the thermally managed Z-scan technique. Particles with spherical shape and 2.6 nm of average diameter were obtained and characterized by transmission electron microscopy and small angle X-ray scattering. This colloid was highly stable, without the presence of chemical impurities, neither stabilizers. It was observed that this system presents a large refractive third-order nonlinear response and a negligible nonlinear absorption. Moreover, the evaluation of the all-optical switching figures of merit demonstrated that the colloidal nanoparticles prepared by sputtering deposition have a good potential for the development of ultrafast photonic devices.