Mitsuzo Arii

Fabrication of SiO2-GeO2 glass optical waveguides by the gas-phase doping method

A new method of fabricating silica glass optical waveguides has been developed. Porous silica glasses made by the sol-gel method were used as substrates, into which a dopant was introduced by utilizing the adsorption equilibrium between porous glass and vapor of the relevant dopant material. Index distributions within the glass were produced by placing the doped glass under reduced pressure to outgas the dopant from the surface of the glass, followed by transforming the dopant into oxide by hydrolysis, and then the porous glass was densified to give nonporous glass. Combining this method with the selective photopolymerization method, where the undesired portion of pores was clogged by polymer, 3D waveguides have been fabricated. The SiO2–GeO2 waveguides thus fabricated have index differences of more than 0.02 with the propagation loss of less than 1 dB/cm.