Buried double waveguide by ion implantation in quartz

Ion implantation may be used to produce barrier-confined optical waveguides in many crystalline materials by decreasing the refractive index in the nuclear stopping region at the end of the ion’s track. In quartz this is particularly effective as the nuclear damage soon saturates at ∼5%, and also practically no index change occurs along the initial part of the track, thus enabling multiple-energy implants to produce broad, flat barriers. We report the use of this technique in the construction of a device with two such barriers at different depths, thus producing a pair of overlayed waveguides. The profile of this composite system could not be determined by any conventional mode analysis method, and so we have extended our dark mode reflectivity technique to cope with multiple barriers. It has proved a very powerful tool for this application, able to probe at sufficient depth below the surface to supply accurate information about the entire double profile.