Free-radical photocurable hybrid material was used for the creation of crack free holographic gratings, showing only a refractive index modulation. Organic-inorganic materials based on the sol-gel synthesis of alkoxysilanes have demonstrated their great potential for coating and optical applications. In a first step, hydrolysis and condensation reactions were led under mild conditions along the same way as in classical sol-gel glasses. Partial elaboration of the silicate backbone was thus achieved. Then, with the use of a photoinitiator, free-radical polymerization was proceeded by irradiating the material under UV or visible light. A spatially controlled photopatterning can be thus achieved to create optical elements having the hardness of a glass-like material. The presented results concern the formation of gratings created by transmission using interference pattern at 514 nm. Diffraction efficiencies up to 90 % were reached for 1000 lines/mm in transmission, corresponding to a refractive index modulation amplitude of 4.10^-3 (according to the Kogelnik's theory). To elaborate non linear quadratic optical devices, hybrid sol-gel matrixes were doped with push-pull chromophores. Such a photosensitive system enables simultaneous photopatterning of the layer and poling of the NLO molecules. Experiments were realized during the photopolymerization step, in order to study the freezing of the non-centrosymetric orientation of the dispersed NLO chromophores.

Date Published: 8 June 2005
PDF: 8 pages
Proc. SPIE 5827, Opto-Ireland 2005: Photonic Engineering, (8 June 2005); doi: 10.1117/12.605806

Published in SPIE Proceedings Vol. 5827:
Opto-Ireland 2005: Photonic Engineering
Thomas J. Glynn; Gerard M. O'Connor; Aidan J.H. Flanagan; Gerald Byrne; Jonathan Magee; John T. Sheridan; Ronan F. O'Dowd; Gerard D. O'Sullivan; Brian W. Bowe, Editor(s)