F2-laser writing of silica optical waveguides in silicone rubber

F2-laser writing of silica (SiO2) optical waveguides has been successfully demonstrated on the surface of silicone [(SiO(CH3)2)n] rubber by the photochemical modification of silicone into silica. The 2-mm-thick silicone rubber was exposed to the 157-nm F2-laser beam through a thin (~0.2 mm) air layer. A proximity Cr-on-CaF2 photomask with 8- to 16-micron-wide slits controlled the exposure size to define the width of the silica waveguide. Optimum laser conditions to generate crack-free waveguides with good transparency were found by varying the laser fluence, pulse repetition rate and total exposure. The optimized waveguides were found to guide both red (~635-nm) and infrared (~1550-nm) wavelengths with light end-fired from standard single-mode fiber.