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New methods for modal characterization of silica waveguides using UV-induced Bragg gratings are proposed. These methods rely either on the filtering of the fundamental optical mode with a Bragg filter or on the mode coupling by tilting the Bragg grating relative to the optical axis. Both theoretical and experimental results are reported.

A novel hybrid structure for optical modulation and switching is presented. It consists of a thin film of electro-optic polymer spin-coated on passive waveguide made by ion exchange on glass substrate. Two structures corresponding to weak guiding and strong guiding conditions are considered. Design issues and modulation performances are studied for the two structures. Low half-wave voltages less than 10 volts are expected for an interaction length of 1 cm provided the electro-optic coefficient of the nonlinear polymer is 10 pm/V.

A new technique based on the use of polymer to drastically decrease the temperature sensitivity of Bragg gratings realised on planar silica waveguides deposited on silicon is proposed. Moreover, this technique suppresses the polarisation dependence of the Bragg filters.

A critical step in the fabrication of polycrystalline silicon thin-film transistors (TFT's) is to crystallize the amorphous silicon layer deposited on glass. This paper describes a complete rapid thermal annealing (RTA) process applied to the crystallization of the amorphous layer. The RTA heating and cooling rates have been optimized to minimize thermal gradients and to improve glass substrate stability. Numerical simulations taking into account the lamp characteristics, the annealing chamber configuration and the sample properties have been developed and allow elucidation of thermal nonuniformities in the sample during the RTA process. Although the transition point of a glass (T g) is often considered as an upper limit in usual polysilicon TFT's processes, this paper shows that if the cooling rate is accurately controlled, annealing temperatures can be above T g without thermal damage to the glass.

This letter describes a new process for realization of polysilicon thin-film transitors (TFT) on glass substrates. The process is based on crystallization by rapid thermal annealing of amorphous silicon films deposited by low-pressure chemical vapor deposition (LPCVD). With this technique, the time of crystallization of the silicon films is reduced to a few seconds. Thin-film transistors have been realized using this process, and the field-effect mobility is in the range of 20 cm2·V-1·s-1.