Ion-implantation-induced densification in silica-based glass for fabrication of optical fiber gratings

Ion implantation induces a refractive index increase in silica-based glass, which is mainly due to densification of the glass. The refractive index increase can be used to fabricate optical fiber gratings that are formed with periodic refractive index modulation in the core of an optical fiber. In this article, the generation mechanism of the densification has been investigated through measurements of thickness changes of silica glass induced by proton and He²⁺ ion implantation. Furthermore, fabrication of the optical fiber grating using the refractive index increase has been demonstrated. From the result, ideal implantation conditions to fabricate the gratings are discussed.