Abstract
Relations between fabrication conditions and optical characteristics of planar waveguides made by proton exchange in benzoic acid are documented in the literature, but reports on the characterization of waveguide fabrication processes, performed in a systematic way, could not be found, resulting in the need to combine data from several authors. Discrepancies among results from different researches are evident, resulting from different experimental methodologies and calibration of equipment. Therefore, aiming at extracting a consistent data set, optical characterization of the refractive index profile was employed to study series of samples. The objective was to develop a methodology for fabrication of proton-exchanged channel waveguides in LiNbO3 operating in the single-mode regime at several wavelengths, with specific characteristics required to optimize integrated devices. To achieve this, it is necessary to obtain the relations between the optical characteristics of the waveguides and their fabrication conditions, and to introduce models of the waveguide formation process. (c) 2007 Society of Photo-Optical Instrumentation Engineers.

Abstract
The possibility of fabricating efficient optical amplifiers in LiNbO3, realized by localization of the dopant on surface areas was theoretically evaluated and the feasibility of fabricating efficient amplifiers in such doped structures was experimentally verified. The model of amplifiers based on 3-level laser systems realized by local doping incorporates dopant localization, the influence of the interaction length, as well as that of the effective pump area and of the pump power in the amplifier performance. It was verified that localized doping allows optimization of amplifier performance through adjustment of the active region geometry to the mode intensity profile. The experimental results confirmed that the width of the metal stripe deposited on the surface must be optimized so that gain is maximum, for a given value of the pump power. It was experimentally demonstrated that transverse localization of the active ions reduces the threshold pump power, which may be relevant for realization of integrated lasers in Er:LiNbO3.

Abstract
Modelling of laser oscillation at 0.9 mu m in Ti waveguides in LiNbO3 doped with Nd ions is presented. Laser emission at 0.9 mu m in Ti waveguides in Nd:LiNbO3 crystals was recently demonstrated. However, lasing was reported as unstable and lasting only a few seconds, with parasitic lasing at the higher gain transition at 1.08 mu m shown to be a problem. In this work the possibility of obtaining efficient and stable laser oscillation at 0.9 mu m in Ti:LiNbO3 waveguides, fabricated in substrates doped with Nd ions by thermal diffusion of thin metallic stripes or planar thin films, was theoretically evaluated. It was concluded that emission at 0.9 mu m, with complete suppression of the parasitic emission at 1.08 mu m, should be possible by selective increase of the losses at 1.08 Irm, through optimization of waveguide and laser cavity, spatial localization of the Nd ions and the use of the dependence on polarization of the emission cross sections at 0.9 and 1.08 mu m.

Abstract
An investigation on optical amplification in Ti waveguides in LiNbO3 doped with Er ions by thermal diffusion of thin metallic stripes is presented. The possibility of fabricating efficient optical amplifiers in LiNbO3 substrates realized by localization of the dopant on surface areas of the crystals was theoretically evaluated and the feasibility of fabricating efficient amplifiers in such doped structures was experimentally verified. It was concluded that the localized doping technique allows optimization of amplifier performance through adjustment of the active region geometry to the mode intensity profile.

Abstract
The aim of this study was to assess the antimicrobial effects of myrtle (Myrtus communis L.) essential oil (EO) on pathogenic (E. coli O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679) and spoilage microbiota in beef and determine its minimum inhibitory concentration (MIC) and antioxidant activity. The behavior of LAB, Enterobacteriaceae, Pseudomonas spp., and fungi, as well as total mesophilic (TM) and total psychotropic (TP) counts, in beef samples, was analyzed during storage at 2 and 8 C-degrees in two different packaging systems (aerobiosis and vacuum). Leaves of myrtle were dried, its EO was extracted by hydrodistillation using a Clevenger-type apparatus, and the chemical composition was determined using chromatographical techniques. The major compounds obtained were myrtenyl acetate (15.5%), beta-linalool (12.3%), 1,8-cineole (eucalyptol; 9.9%), geranyl acetate (7.4%), limonene (6.2%), alpha-pinene (4.4%), linalyl o-aminobenzoate (5.8%), alpha-terpineol (2.7%), and myrtenol (1.2%). Myrtle EO presented a MIC of 25 mu L/mL for E. coli O157:H7 NCTC 12900, E. coli, Listeria monocytogenes ATCC BAA-679, Enterobacteriaceae, and E. coli O157:H7 ATCC 35150 and 50 mu L/mL for Pseudomonas spp. The samples packed in aerobiosis had higher counts of deteriorative microorganisms than samples packed under vacuum, and samples with myrtle EO presented the lowest microbial contents, indicating good antimicrobial activity in beef samples. Myrtle EO is a viable natural alternative to eliminate or reduce the pathogenic and deteriorative microorganisms of meat, preventing their growth and enhancing meat safety.

Abstract
Continuous monitoring of hydrogen (H2) concentration is critical for safer use, which can be done using optical sensors. Palladium (Pd) is the most commonly used transducer material for this monitoring. This material absorbs H2 leading to an isotropic expansion. This process is reversible but is affected by the interaction with interferents, and the lifetime of Pd thin films is a recurring issue. Fiber Bragg Grating (FBG) sensors are used to follow the strain induced by H2 on Pd thin films. In this work, it is studied the stability of Pd-coated FBGs, protected with a thin Polytetrafluoroethylene (PTFE) layer, 10 years after their deposition to assess their viability to be used as H2 sensors for long periods of time. It was found that Pd coatings that were PTFE-protected after deposition had a longer lifetime than unprotected films, with the same sensitivities that they had immediately after their deposition, namely 23 and 10 pm/vol% for the sensors with 150 and 100 nm of Pd, respectively, and a saturation point around 2 kPa. Furthermore, the Pd expansion was analyzed in the presence of H2, nitrogen (N2), carbon dioxide (CO2), methane (CH4) and water vapor (H2O), finding that H2O is the main interferent. Finally, an exhaustive test for 90 h is also done to analyze the long-term stability of Pd films in dry and humid environments, with only the protected sensor maintaining the long-term response. As a result, this study emphasizes the importance of using protective polymeric layers in Pd films to achieve the five-year lifetime required for a real H2 monitoring application.