Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
20 records were found.
We describe the first non-destructive measurements of the evolution of the optical continuum along a non-linear waveguide. By utilizing near-field microscopy, the spectral variation can be imaged along and across the waveguide with sub-wavelength resolution.
A novel method for designing photonic crystals with high orders of rotational symmetry using an inverse Fourier transform (IFT) method is presented. The IFT of an n-sided polygon is taken and the positions of the peaks are computed in order to obtain a set of discrete points in real space where the scattering centres are to be located. We show, by simulating the diffraction pattern, that although these points appear disordered they possess long range order, which also confirms that the arrangement of points has n-fold rotational symmetry. The designed structures can possess an arbitrary number of rotational symmetries, whilst retaining the sharp diffraction patterns characteristic of known crystal lattices which exhibit wide bandgaps. We present simulation results using the finite difference time domain method (FDTDM) for large non-rep...
Measurement of spectral interference with a near-field scanning optical microscope is used to determine directly the variation of group velocity between modes of a planar slab waveguide as the modes propagate along the guide.
The far-field profile of photonic quasi-crystal patterned
and unpatterned LEDs, fabricated from commercial epitaxial
substrates by electron beam lithography, has been measured
prior to lapping and dicing. Emission enhancements reach a maximum
of 62%, and are strongly dependent on the filling factor.
Qualitative agreement is achieved between 2-D finite-difference
time-domain calculations and the experimental data.
Comprehensive reflectivity mapping of the angular dispersion of nanostructured arrays comprising of inverted pyramidal pits is demonstrated. By comparing equivalently structured dielectric and metallic arrays, diffraction and plasmonic features are readily distinguished. While the diffraction features match expected theory, localised plasmons are also observed with severely flattened energy dispersions. Using pit arrays with identical pitch, but graded pit dimensions, energy scaling of the localised plasmon is observed. These localised plasmons are found to match a simple model which confines surface plasmons onto the pit sidewalls thus allowing an intuitive picture of the plasmons to be developed. This model agrees well with a 2D finite-difference time-domain simulation which shows the same dependence on pit dimensions. We believe the...
A novel method for designing photonic crystals with high orders of rotational symmetry using an inverse Fourier transform (IFT) method is presented. The IFT of an n-sided polygon is taken and the positions of the peaks are computed in order to obtain a set of discrete points in real space where the scattering centres are to be located. We show, by simulating the diffraction pattern, that although these points appear disordered they possess long range order, which also confirms that the arrangement of points has n-fold rotational symmetry. The designed structures can possess an arbitrary number of rotational symmetries, whilst retaining the sharp diffraction patterns characteristic of known crystal lattices which exhibit wide bandgaps. We present simulation results using the finite difference time domain method (FDTDM) for large non-rep...
Comprehensive reflectivity mapping of the angular dispersion of nanostructured arrays comprising of inverted pyramidal pits is demonstrated. By comparing equivalently structured dielectric and metallic arrays, diffraction and plasmonic features are readily distinguished. While the diffraction features match expected theory, localised plasmons are also observed with severely flattened energy dispersions. Using pit arrays with identical pitch, but graded pit dimensions, energy scaling of the localised plasmon is observed. These localised plasmons are found to match a simple model which confines surface plasmons onto the pit sidewalls thus allowing an intuitive picture of the plasmons to be developed. This model agrees well with a 2D finite-difference time-domain simulation which shows the same dependence on pit dimensions. We believe the...
The far-field profile of photonic quasi-crystal patterned and unpatterned LEDs, fabricated from commercial epitaxial substrates by electron beam lithography, has been measured prior to lapping and dicing. Emission enhancements reach a maximum of 62%, and are strongly dependent on the filling factor. Qualitative agreement is achieved between 2-D finite-difference time-domain calculations and the experimental data.
Photonic crystal based active devices and their monolithic integration with passive photonic circuits such as waveguides, combiner structures, and examples of surface normal coupling are discussed.
This paper describes a unique way of designing highly complex photonic nanostructures. hotonic Quasicrystals have far reaching applications in many areas of photonics including light extraction from LEDs and for the fabrication of "slow-light" devices or optical delay lines. However, it is not straightforward to produce the e-beam writer data file to produce an arbitrary symmetry photonic quasicrystal as a "lattice" as such does not exist. The location of the photonic crystal scattering centres are found by an inverse method. Starting with the n-fold diffraction pattern, where n is either 5-fold or in excess of 6-fold symmetry, an inverse Fourier transform is taken which will indicate the real space location of the scattering centres. This procedure greatly simplifies the fabrication of highly complex photonic quasicrystal devices...
