Photosensitivity of sol-gel-derived nanocomposites in optical device deposition: an in-situ spectroscopic study

摘要

An in situ waveguide Raman spectroscopy experiment was designed to monitor structural changes that occurred when a hybrid sol gel glass thin film was irradiated with UV light. Raman scatter was collected from an Ar$+$PLU$/ laser 514.5 TE$-0$/ mode excited in the waveguide. Insight into the photoinduced changes in the glass was obtained by collecting real time WR spectra as the slab waveguide was irradiated simultaneously with UV light. Photoinduced polymerization of the organic group is linked to enhanced inorganic network formation. Silicon centers are brought closer together as their covalently attached methacrylate substituents oligomerize upon irradiation. This promotes further polycondensation reactions between residual Si-OH and residual Si-OCH$-3$/ groups. The resulting siloxane bonds contribute to the growth of the silicate matrix. This photodensification process leads to volume compaction of the matrix and hence to an increase in the material refractive index.