Silica waveguide structure

Abstract From the Canadian patent

A three-dimensional waveguide has path regions which share a common confining region, preferably of uniform refractive index. The path regions are located at two or more levels. The structure is implemented in silica with distributed dopants to distinguish path regions from the confining region. The structure is made using flame hydrolysis to deposit layers. Melting point depressants are incorporated so that later deposited layers can be melted without melting the whole structure. Some layers of pure silica can be deposited by chemical vapour deposition. These layers are never melted and they provide a stabilising skeleton when complicated structures are melted.