Abstract
Precisely aligned transparent fused-silica (SiO2) microspheres 2.5 µm in diameter were nonthermally welded to silicone rubber by 157 nm F2-laser-induced photochemical modification of the silicone into silica. A short exposure to the F2 laser of ∼10 mJ/cm2 single-pulse fluence, 10 Hz pulse repetition rate and 600 pulses was required for sufficient photochemical welding. The welding strength depended on the extent of the silica formation, which was controlled by F2 laser exposure. Silica formation occurred even in silicone underneath the microspheres due to the F2 laser decomposition of oxygen molecules dissolved in the silicone. A cross-sectional atomic force microscope image of silicone underneath the microspheres after welding revealed that a large contact area between the silicone and the microspheres was formed. After welding, the aligned silica microspheres were butt-coupled to a tapered silica optical fiber ∼2.5 µm in diameter for optical waveguide applications. The alignment was found to have the capability of guiding red (635 nm)-wavelength light.