An integrated photonic apparatus that includes a glass substrate having a major
surface, wherein the glass substrate includes a plurality of regions, each region
having a different index of refraction, including a first region having a first
index of refraction and a second region having a second index of refraction lower
than the first index of refraction, and a first waveguide formed along the major
surface of the substrate, wherein the first waveguide has a higher index of refraction
than an intrinsic index of refraction of adjacent portions of the substrate, and
wherein the first waveguide passes through the first region and through the second
region of the glass substrate.