A graded index of refraction optical waveguide is formed in interlayer
dielectric material located above a substrate an integrated circuit-like
structure. The waveguide includes a refractive layer of optically
transmissive material surrounding a core of optically transmissive
material within a trench in the dielectric material. The material of the
core has a higher index of refraction than the refractive layer and the
material of the refractive layer has a higher index of refraction than the
dielectric material. More than one refractive layer may also be formed in
the trench, with the inner refractive layer having an index of refraction
higher than the outer refractive layer and less than the core.
