Optimisation of borophosphosilicate glass compositions for silica-on-silicon integrated optical circuits fabricated by the sol-gel process

Silica-on-silicon channel guide devices fabricated in sol-gel borophosphosilicate glass deposited by repetitive spin-coating and rapid thermal annealing (SC-RTA) are described. Process parameters for a wide range of glass compositions are given. The optimum performance is obtained using a borosilicate buffer layer, a phosphosilicate core and a borophosphosilicate cladding with a low melting point. Low-loss thermo-optic interferometric modulators fabricated by this process are described.