Abstract
Symmetric buried channel waveguides fabricated on silicon substrates by the organic-inorganic hybrid sol-gel process are reported. The buffer/cladding layer material is composed of methyl-modified silanes and presents high network flexibility and low refractive index, at low cost. Film thickness above 10 mum is possible without cracks, even after thermally baking the films at 150degreesC, and the refractive index is 1.468 at 632.8 nm. The influence of the methylsiloxane species on the material absorption loss was investigated, in particular at 1.55 mum. For channel waveguide core definition, a photopatternable layer was polymerised by 248 nm laser radiation through an amplitude mask, and the unexposed material was simply removed by an organic solvent. The transmission spectrum of the waveguides is presented and reveals an acceptable loss level of 0.3dB/cm at 1300 nm, but larger loss in the 1550 nm region. The procedure developed is compatible with optoelectronic integration in silicon.

Abstract

Abstract
Owing to the limited spectral response of the fiber directional coupler used in a balanced optical coherence tomography configuration, the spectra are different in the two outputs. This affects unfavorably operation of the balanced photodetector unit. Excess photon noise makes a larger contribution than a directional coupler with a flat spectral response. A theoretical model is developed that shows that an optimum set of parameters may be defined to maximize the achievable signal-to-noise ratio. The model leads to a redefinition of the effective noise bandwidth, which takes into account the nonflat response of the directional coupler used. The model also predicts a limitation on the signal-to-noise ratio even when the stray reflectances in the interferometer are brought to zero. (C) 2004 Optical Society of America.

Abstract
Motivated by the large application of the CDCC method (continuum discretized coupled channel method) to reactions with dripline nuclei of two body nature A = c + p, we study the behaviour of these couplings for a low energy breakup scenario, where they play a crucial role. Continuum couplings can produce a variety of effects on reaction observables. Based on previous calculations, we investigate their range and their dependence on the relative angular momentum and the relative energy between the pair. The conclusions of this work can help design a more efficient model space for the two body continuum. (C) 2004 Published by Elsevier B.V.

Abstract
In optical coherence tomography (OCT), it is often assumed that the signal-to-noise ratio, at higher optical power regimes, is limited by beat noise. Nonetheless it was often noticed that the limiting value could not be experimentally achieved, despite minimizing the stray reflectance and increasing the optical source effective bandwidth. In this work we present a new model for the noise in a balanced OCT configuration, which accounts for the limited spectral response of fiber directional couplers, as well as imperfections in the photo-detectors. As a consequence, and due to different spectrum content between the two balanced-OCT outputs, excess photon noise is larger than previously considered. The model also allows for the determination of SNR optimized parameters for maximum performance of the balanced system, and can be applied to any coupler or broadband source. Results for optimized and non-optimized configurations, for different balanced detection configurations, implemented in an OCT system, are presented and discussed.

Abstract
A simple method for crystallizing amorphous thin films was developed using platinum bottom electrodes as heating elements. A current was applied to tungsten wires in contact with the platinum and the temperature was measured using a type-K thermocouple. A proportional feedback algorithm was used for controlling the process. The performance of different platinum electrodes was studied. Pt films with different thicknesses were alternatively deposited over Ti and Zr at 700degreesC. Applying currents up to 2 A to the Pt films, the resistance dependence of temperature was studied. The maximum temperature, 675degreesC, was obtained when using 200 nm Pt films deposited at 700degreesC over Ti, with a power consumption of 16 W. The method was applied to the crystallization of PbZr0.52Ti0.48O3 thin films using Pt films deposited at 500degreesC over Ti and at 700degreesC over Zr. The results obtained for heat treatments at 650degreesC with 10degreesC/s heating and cooling rates showed a pure perovskite phase; the ferroelectric properties were comparable with those from films crystallized by rapid thermal annealing. (C) 2004 American Institute of Physics.