Furance and carbon dioxide laser densification of sol-gel derived silicon oxide-titanium oxide-aluminum oxide planar optical waveguides

Abstract

An experimental investigation on the furnace and CO₂ laser densification of sol-gel derived SiO₂-TiO₂-Al₂O₃ planar optical waveguides was performed. Solutions containing equal mole fractions of tetraethoxysiline [Si(C₂H₅O)₄], titanium ethoxide [Ti(C₂H₅O)₄], aluminum tri-sec-butoxide [Al(C₄H₉O)₃] were used to spin films with a nominal 2:2:1 molar SiO₂-TiO₂-Al₂O₃ composition. Emphasis was placed on determining what effects the densification techniques had on film shrinkage, index change, crystallization and composition. Film shrinkage and refractive index change were found to be similar for both densification techniques. Fully dense, amorphous film were obtained with both methods. After densification, further heating caused titania crystalline phases to form with both processing techniques. However, anatase formed in the furnace fired films while rutile formed in the laser irradiated films.