Abstract
Phase-shifted Bragg grating waveguides (PSBGWs) were formed in bulk fused silica glass by femtosecond laser direct writing to produce narrowband (22 +/- 3) pm filters at 1550 nm. Tunable p and other phase shifts generated narrow passbands in controlled positions of the Bragg stopband, while the accurate placement of multiple cascaded phase-shift regions yielded a rectangular-shaped bandpass filter. A waveguide birefringence of (7.5 +/- 0.3) x 10(-5) is inferred from the polarization-induced spectral shifting of the PSBGW narrowband filters. (C) 2012 Optical Society of America

Abstract

Abstract
The retinal fundus images are used in the treatment and diagnosis of several eye diseases, such as diabetic retinopathy and glaucoma. This paper proposes a new method to detect the optic disc (OD) automatically, due to the fact that the knowledge of the OD location is essential to the automatic analysis of retinal images. Ant Colony Optimization (ACO) is an optimization algorithm inspired by the foraging behaviour of some ant species that has been applied in image processing for edge detection. Recently, the ACO was used in fundus images to detect edges, and therefore, to segment the OD and other anatomical retinal structures. We present an algorithm for the detection of OD in the retina which takes advantage of the Gabor wavelet transform, entropy and ACO algorithm. Forty images of the retina from DRIVE database were used to evaluate the performance of our method.

Abstract

Abstract
Femtosecond laser exposure produces form and stress birefringence in glasses, mainly controlled by laser polarization and pulse energy, which leads to challenges in certain applications where polarization mode dispersion or birefringence splitting is critical for the desired responses from optical devices. In this paper, parallel laser modification tracks with different geometries were applied to preferentially stress the laser-written waveguides and explore the possibility of tuning the waveguide birefringence in devices fabricated in bulk fused silica glass. Polarization splitting in Bragg grating waveguides showed the laser modification tracks to controllably add or subtract stress to the pre-existing waveguide birefringence, demonstrating independence from the nanograting induced form birefringence and the contributions from material stress. Stressing bars are shown that offer tunable birefringence in the range from similar to 0 up to 4.35 x 10(-4), possibly enabling great flexibility in designing polarization dependent devices, as well as making polarization independent devices. (C) 2012 Optical Society of America

Abstract
The paper presents a proposal high-level model for the development of Educational Collaborative virtual Environments based on engineering software and quality concepts for software development. A life cycle was identified, which was detailed the phases of development, taking into account different techniques and methods and related documentation. The main goal of this research is to demonstrate how we can use the model to develop our applications by virtual world's platforms. The model was conceived based on research carried out in area the development of models that integrate all phases of process development software and models for assessing collaborative virtual environments. The model used contains a set of diagrams to support developer teams in their tasks, mainly in the creation of educational collaborative virtual environments to be used in an e-learning context. © 2012 IEEE.