Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
38 records were found.
In this paper we investigate improvement in performance attainable by etching Photonic Crystals and Photonic Quasi-Crystals into the top emitting surface of LEDs. We describe the physical mechanisms of extraction enhancement through ordered surface patterning and investigate benefits in terms of total extraction enhancement, beam directionality, and far field beam quality. Factors such as lattice geometry, etch depth, and epitaxy thickness are investigated. We show that a great variety of far field beam profiles of benefit in applications such as projection TV light engines and direct flat panel display illumination can be obtained simply by adjusting geometric design parameters. Our results show that PCs can provide significant improvement in extraction enhancement for applications requiring non Lambertian beam shapes when etched into...
We demonstrate experimentally the tuning of complete photonic band gaps in patterned silicon nitride waveguides. Transmission measurements were performed using an ultrabroadband high-brightness white light laser continuum, extracting extinction ratios as low as 10–4 in the gap regions. Angle-resolved measurements show the perfect alignment of the gap around the -J direction. © 2000 American Institute of Physics. [S0003-6951(00)02008-8]
We report a reproducible top down fabrication procedure for a single domain wall magnetoresistance H-shaped device. A bi-layer e-beam lift-off process is used and the e-beam exposure dose sensing technique and proximity effect correction are discussed, together with a method to reduce the alignment tolerance to below 20 nanometer. The domain wall width is constrained down to 37nm and room temperature domain wall magnetoresistance ratio of 0.3% was detected. The dependence of switching magnetic field to domain width will be discussed, as well as the maximum domain width which can retain its magnetisation aligned along the long axis at zero field which is found to be 210nm in our experiment.
It is firmly established that periodic lattice structures can support photonic bandgaps (PBG). However, complete and absolute photonic bandgaps (CAPBG) have only been achieved in high dielectric constant mediums such as GaAs (=13.6). An artificial quasiperiodic photonic crystal based on the random square-triangle tiling system was designed and fabricated. The photonic quasicrystal possesses 12-fold symmetry and was analysed using a finite difference time domain (FDTD) approach. High orders of symmetry in photonic quasicrystals have been shown to provide isotropic bandgaps across all the directions of propagation of light. As an outcome of these properties, this new class of photonic quasicrystal has been shown, for the first time, to possess a secondary non-directional CAPBG for a relatively low index material, silicon nitride (=4.08)....
We demonstrate experimentally the tuning of complete photonic band gaps in patterned silicon
nitride waveguides. Transmission measurements were performed using an ultrabroadband
high-brightness white light laser continuum, extracting extinction ratios as low as 1024 in the gap
regions. Angle-resolved measurements show the perfect alignment of the gap around the G-J
direction.
Thin films of Yttrium Oxide, Y2O3 were deposited by reactive sputtering and reactive evaporation to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The optical properties, structure and crystalline phase of the films were found to be dependent on the deposition method and process parameters. X-ray diffraction (XRD) analysis on the 'as-deposited' thin films revealed that the films vary from amorphous to highly crystalline with a strong peak along the <222> plane of Y2O3. The samples with the polycrystalline structure had a stoichometry close to bulk cubic Y2O3. SEM imaging revealed a regular column structure confirming their crystalline nature. The thin film layers which allowed guiding in both the visible and infra-red region had lower refractive indices, higher oxygen content and had a...
We demonstrate experimentally the tuning of complete photonic band gaps in patterned silicon nitride waveguides. Transmission measurements were performed using an ultrabroadband high-brightness white light laser continuum, extracting extinction ratios as low as 10–4 in the gap regions. Angle-resolved measurements show the perfect alignment of the gap around the -J direction. © 2000 American Institute of Physics. [S0003-6951(00)02008-8]
Gallium lanthanum oxysulfide (GLSO) is a promising host material for observing strong upconversion emission from trivalent rare-earth ions such as erbium (Er3+). Its attractive properties include high rare-earth solubility due to the lanthanum content of the glass former, a high refractive index (n = 2.2 at 550nm) for high radiative efficiency, and a low maximum phonon energy of approximately 425cm-1. Photonic crystals meanwhile can provide controlled light extraction, and may be capable of suppressing unwanted IR emission from lower lying metastable states. Here, we describe the fabrication of photonic crystals in annealed films of Er3+-doped GLSO deposited by RF sputtering. The most intense visible upconversion emission is observed in films annealed at 550°C, close to the bulk glass transition temperature. Hexagonal lattice photonic ...
