A inteligibilidade da palavra em igrejas católicas, através de análises de carácter objectivo e subjectivo
Lencastre, Margarida Maria Mendes de Freitas de Queiroz e
1988-01-01
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It is likely that the commercialisation of Photonic Crystal (PC) technology will require the high-volume capabilities provided by semiconductor nanofabrication processes. To this end, a Silicon-compatible PC waveguide could form the basic building block of an all-optical circuit. This presentation will discuss the development of PC research at Southampton University (UK) which began with deep photoelectrochemically etched holes in single-crystal Silicon. This initial work progressed to an all dielectric waveguide structure on a Silicon substrate, with the materials utilised being compatible with a CMOS process. PC nanofabrication and optical characterisation using these waveguiding structures will be described in detail.
A method for the reliable attachment of oligonucleotides to silicon (100) surfaces in patterns is described. UV light exposure of silicon (100) coated with alkenes functionalized with carboxylic acid groups and derivatives results in covalent attachment to the silicon surface. The carboxyl-terminated (and derivatives) surfaces act as a substrate for the chemistry of the subsequent attachment of oligonucleotides. Illustrated are our results gained for optimisation of the surface attachment chemistry and the characterisation of the surface with scanning electron microscopy, epifluorescence microscopy and ellipsometry.
A method is presented for the covalent attachment of oligonucleotides to silicon (100) surfaces patterned with micron-scale features. UV light exposure of hydrogen-terminated silicon (100) coated with alkenes functionalized with N-hydroxysuccinimide ester groups results in Si-C bonded monolayers. The N-hydroxysuccinimide ester surfaces act as a template for the subsequent covalent attachment of DNA oligonucleotides. In order to create patterns of surface attached DNA oligonucleotides with high density, the surface attachment chemistry has been investigated and optimised. Micron scale patterning of surfaces was achieved by exposure with UV laser light via a mask. DNA oligonucleotide patterns, with feature sizes of several microns, were reliably produced over large areas. The patterned surfaces were characterised with scanning electron m...
Ultrafast optical gating was used to resolve the time of flight of photons through photonic crystal waveguides. We observed the slowing down of light around the band gap.
This paper reviews data acquisition, transmission and processing methodologies for continuous online monitoring of partial discharges in power cable systems. A PD continuous online monitoring system for underground cable circuits using capacitive couplers, LiNbO electro-optic modulators, laser, optical switch and optical fibers has been proposed. Data processing methods include pulse shape and spectrum analysis, time of flight analysis, phase-resolved two-dimensional histograms, three-dimensional φ-q-n patterns, trend analysis, wavelet-based denoising, alarm strategy and telecommunication function to enable remote control and data download.
This paper describes the further development of a novel partial discharge continuous monitoring technique. The measurement mechanism applies capacitive coupler measured partial discharge signals across a LiNbO3 electro-optic modulator to modulate the intensity of the transmitted laser light. Recent research has applied an in-fine fibre polarizer for use with the modulator. A polarization scrambler is placed after the laser source to generate unpolarized light, which is transmitted over long length of standard single mode fibres and fed to the fibre polarizer and the modulator. Both the fibre polarizers and modulators, which are placed near cable joints, are passive without any power requirement.
In this work we determine the thermo-optical properties of two chalcogenide glasses (in mo1%): 65 Ga2S3; 30 La2S3; 5 La2S3 (GA:La:S) and 72.5 Ga2S3; 27.5 La2O3 (Ga:La:S:O). The thermal relaxation calorimetry and the thermal lens technique were combined so that the samples specific heat, thermal diffusivity, thermal conductivity, and the temperature coefficient of the optical path length change could be measured. Our results indicate that changes in thermal diffusivity (~2.7 x 10-3 cm2/s) and conductivity (~4.8 x 10-3 W/K cm) observed when La2O3 is added in the glass compounds are less than the error in the data.
Ultra-high bandwidth continua generated by ultrashort fs pulses have been attracting enormous interest for applications such as general spectroscopy, Optical Coherence Tomography and metrology. Dispersion engineering is one of the key aspects of optimised continuum generation in optical waveguides. However in addition, the dispersion of the pump pulse can be continuously adapted to control bandwidth and spectral characteristics of the generated continua. In this work we report on a systematic investigation of how 2nd,and 3rd order dispersion affects the continuum generated in strongly non linear planar waveguides. A -30 fs Ti:Sapphire tuned to 800 nm was used as a pump source delivering ~3 nJ pulses. The chirp of the pulses was controlled completely-arbitrarily by an acousto-optic programmable dispersive filter (Dazzler). The power lau...
The fabrication and operation of Ti:sapphire channel-waveguide lasers is presented, in which both the gain medium and the waveguide are formed by the thermal diffusion of titanium. Lasing was observed between wavelengths of 775 nm and 821 nm, with the lowest launched pump-power threshold being 210 +/- 40 mW for a pump wavelength of 514.5 nm.
We report the fabrication of a linear array of self-assembled polystyrene microspheres side coupled to a rib waveguide. The optical coupling between the lateral evanescent field and the periodically perturbed effective refractive index alongside the waveguide results in a transmission stopband at the Bragg wavelength. The observed transmission spectrum shows a notch centered at lambdaapproximate to1590 nm, which is in close agreement with theory. The coupling coefficient, kappa, and the spectral response are derived for variable cladding medium index using perturbation theory. Structures of this type are expected to find application in wavelength selection, optical sensing, and optical delays.
