Abstract
Hybrid sol-gel technology has proved its usefulness in the field of micro-optics. Indeed, it makes it possible to manufacture optical microcomponents by processes much simpler than those currently used, particularly when photopatternable materials are employed. However, for wavelengths in the near infrared window (NIR), this process is confronted with a major problem which results from the significant optical absorption of this type of materials, in particular around 1550 nm. The aim of this paper is to describe the origin of the losses of some hybrid sol-gel materials of direct interest in micro-device fabrication in order to propose solutions to achieve a greater transparency in the NIR region. The intrinsic absorption of the precursors was first of all considered since it is crucial to pursue the final goal of decreased losses. Then, the principal parameters of the sol-gel synthesis were studied. Among them, the thermal treatment conditions, the hydrolysis ratio and the controlled addition of transition metal alkoxides allow an improvement of the material transparency, at 1550 nm most particularly. This last point was considered with the highest attention, and NIR and NMR spectroscopies were employed to explain how the addition of zirconium alkoxides at the end of the reaction makes it possible to considerably decrease the losses in the material.

Abstract
The fabrication and characterisation of Long Period Gratings in fibre tapers is presented alongside supporting theory. The devices possess a high sensitivity to the index of aqueous solutions due to an observed spectral bifurcation effect.

Abstract
A new transmissive grating-based scanning delay-line for optical coherence tomography is proposed, with dispersion compensation capability. Compared to other spectral delay-lines, our implementation has less loss due to a halved number of diffraction grating reflections, and implements a walk off compensation scheme. The performance of the delay line is evaluated. The delay line transmissive geometry targets balance detection configurations. © 2005 SPIE and OSA.

Abstract
A novel Fourier domain fast scanning optical delay line is proposed in which the walk-off is eliminated by only two passes through a diffraction grating. Working in transmission, the novel delay line is ideal for balanced optical coherence tomography configurations with recirculation of the reference beam. We evaluate theoretically and experimentally its walk-off and dispersion compensation capabilities. (c) 2005 Optical Society of America

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