Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
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108 records were found.
This thesis describes a series of experimental studies on the use of direct bonding for optical waveguide fabrication. The direct bonding technique involves contacting two ultra-clean polished surfaces to form an adhesive-free vacuum-tight bond. Optical materials bonded in this way can be formed into waveguide devices, and this work extends direct bonding to include periodically poled materials and a new solid-state ion-exchange process.
The first result of this work describes the fabrication of a 5.5-mm-long, 12-µm-thick periodically poled LiNbO3 planar waveguide buried in LiTaO3. Frequency doubling experiments performed with this device demonstrate a conversion efficiency of 4.3 %W-1, a value 40% greater than that calculated for an optimised bulk device of similar length.
Also demonstrated is a photorefractive iron-doped LiNbO3...
High-yield zinc-diffused channel waveguides in pre-poled z-cut PPLN with high photorefractive resistance at room temperature are presented. Frequency doubling of a 1064nm Nd:YAG laser at 145°C gave a conversion efficiency of 16.7%/Wcm.
Using an appropriately designed quasi-phase matched structure it is theoretically possible to compensate for the deleterious effects of Gouy phase shift allowing a symmetric frequency response and tighter focussing for higher conversion efficiencies.
We report on the fabrication of bidimensional arrays of hexagonal domains with strictly periodic and quasi-periodic patterns for the implementation of nonlinear photonic crystals and quasi-crystals in z-cut congruent LiNbO3.
In this paper we demonstrate that a positive change in refractive index can be induced by UV radiation in bulk Pyrex, an inexpensive, commercially available glass that is not specifically designed to be photosensitive. We describe the fabrication of channel waveguides in Pyrex by direct UV writing and show that a potassium-ion exchanged layer can be used to host single mode waveguides. The change in refractive index due to the UV writing is found to be 2x10−3.
In this paper we demonstrate that a positive change in refractive index can be induced by UV radiation in bulk Pyrex, an inexpensive, commercially available glass that is not specifically designed to be photosensitive. We describe the fabrication of channel waveguides in Pyrex by direct UV writing and show that a potassium-ion exchanged layer can be used to host single mode waveguides. The change in refractive index due to the UV writing is found to be 2x10−3.
We report the infrared operation of a bulk optical Bragg modulator based on electro-optically induced refractive index gratings in z-cut periodically poled lithium niobate. Efficiencies in the first order of 45% for 1064 nm e-polarized light and 30% for o-polarized light were achieved, with maximum on/off ratios of 15:1 and 9:1, respectively. Field-induced light scattering effects due to poling are observed at higher drive voltages and compromised device performance due to these scattering effects is predicted to limit long-wavelength operation of these devices.
We report the fabrication of a 20-µm-thick photorefractive Fe:LiNbO3 planar waveguide buried in MgO:LiNbO3 by direct bonding of precision polished surfaces. Nonreciprocal transmission measurements were performed in a 3-mm-long device with a continuous wave 532 nm frequency-doubled YAG laser source. A Fresnel-reflection-based counterpropagating beam arrangement was used to measure a relative change in optical density of approximately 2 within the waveguide, with a photorefractive response time of 4.9 ms.
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...
We report a 20-μm-thick Fe:LiNbO3 waveguide buried in MgO:LiNbO3 by direct bonding. Non-reciprocal transmission measurements in a 3-mm-long device with a cw 532 nm source gave a relative change in optical density of 2 and response time of 4-5 milliseconds.
