Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
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The talk will provide an overview of applications of domain inverted materials in optics. In particular, methods of fabrication will be presented with particular emphasis on the interplay between poling techniques, material properties and device requirements. Examples will be presented of nonlinear optical devices in bulk and waveguide. Further examples will concentrate on novel uses of domain engineered devices.
LiNbO3 and LiTaO3 are commonly used ferroelectric crystal materials. Since the first reports of successful single domain crystal growth in 1965, these materials have found increasing use in optoelectronics, laser systems, Q-switching and frequency conversion, holographic data storage, surface acoustic wave devices, integrated optics and modulator use, and most recently, microwave telecommunications. In single domain format these ferroelectrics are photorefractive, pyroelectric and piezoelectric, and possess usefully large nonlinear optical and electro-optical coefficients. If domain engineering or micron/nano-scale bulk or surface modification is performed however, greater functionality is introduced, leading to additional uses such as phase-matched frequency conversion, grating and photonic structures, and the recently proposed use in...
We present a novel technique for producing single-step buried K+-Na+ ion-exchanged waveguides in BK-7. Direct bonding provides atomic contact between chemically modified glass layers, which when heated create a waveguide by intersubstrate ion-exchange.
We report the fabrication and nonlinear optical characterisation of 2-D hexagonally-poled lithium niobate (HEXLN). The various reciprocal lattice vectors of the 2-D format permit multiple noncolinear quasi-phase matching geometries. Second-harmonic conversion efficiencies > 60% are observed.
Ferroelectric materials such as LiNbO3 and LiTaO3 offer many potential advantages over silicon for MEMS structures and self-actuating miniature devices. These materials possess numerous useful intrinsic properties such as piezoelectricity, pyroelectric and electro-optic coefficients, enabling the construction of micron-scale cantilevers, membranes, tips and switches. So far however, reliable and accurate methods for machining and microstructuring LiNbO3 single crystals have been lacking. We have recently been exploring several such methods, which are sensitive to ferroelectric domain orientation. A sample that has been domain-engineered shows a large difference in etch characteristics: the +z face does not etch at all, whereas the -z face etches normally. Microstructured devices can be fabricated therefore, via spatially selective doma...
It is necessary to develop an understanding of the surface discharge behaviour of insulating materials under the influence of high electrical stress. A more recent development is a measurement system that is capable of visualising the dynamic movement of surface discharge. The measurement system is based on the use of a birefringent crystal as the sensing element. The method utilises the electro-optic effect (Pockels effect) of the crystal in order to detect the electric stress within it. A test material is bonded to the backface of the crystal and any surface charge upon it will alter the local field within the crystal. The field will affect the polarisation of light passing through the crystal and the amount of reflected light for a given angle of polarisation can be easily measured. Determining the change in polarisation of the refl...
Asymmetric stepped quantum wells have been used in many optoelectronic devices. This paper proposes a modulation doping position at the edge of the stepped well to minimise the potential distortion caused by the doping. As a result, parasitic potential wells are eliminated, and the sensitivity of the energy levels to dopant concentrations is substantially reduced. We also suggest a stacked design to juxtapose two quantum well slabs in order to improve the waveguide mode overlap in optically pumped terahertz lasers using the structure. The percentage of overlap between the active quantum wells layers and the laser mode increases from 9.8 % for a thinned-substrate single slab scheme to 68.4 % for the stacked double slabs with two highly doped layers acting as a plasma waveguide respectively. A diffraction integral model is established to...
The design of a novel, microfluidic chip with an integrated micro perisaltic pump and chambers for DNA amplification is described. This chip contains three reaction chambers stable at 90 degrees c, 72 degrees C and 55 degrees C for PCR amplificiation, a bi-directional peristaltic pump and optical integrated detection of the droplet. A reactant droplet is to be introduced into the device, pumped back and forth between the chambers for the micro perisaltic pump for sample processing. The static behaviour of the micro pump was modelled theoretically in order to evaluate the optimal dimensions for the membranes and to obtain the maximum flow rate. Thermal analysis by the finite element method was performed to optimize the location of the heaters and the temperature uniformity over the three reaction chambers. Transient thermal analysis ind...
Gallium lanthanum sulphide (Ga:La:S) optical glass is an interesting material, for both fiber and planar technologies, as it offers possibilities for a wide array of devices suitable for use in both non-linear applications and as IR lasers. Direct laser writing into this glass has yielded low loss single mode channel waveguides. Samples were exposed to above bandgap illumination of focused UV (λ=244 nm) light at varying intensities (Iuv = 1.5 to 90 kW/cm2) and scan velocities ( Vscan = 0.005 to 0.067 m/s). The exposed regions were evaluated through atomic force microscopy (AFM) and surface compaction (0.3 - 3.6 μm) was observed. Sample topography was examined using a scanning electron microscope (SEM) with analysis of chemical changes within the exposed regions performed with energy dispersive x-ray microscopy (EDAX). Waveguide attenua...
The wavelength-scale features in holey fibers lead to novel properties including endlessly single-mode guidance, high optical nonlinearity per unit length, and anomalous dispersion below 1.3 μm. Such properties are useful for a wide range of nonlinear fiber devices.
