US Patent 10007061 Three-dimensional (3D) photonic chip-to-fiber interposer

A method of fabricating an optical coupling device, comprising forming a waveguide mask layer on a substrate platform, wherein the waveguide mask layer comprises an array of openings comprising a first end and a second end opposite to the first end, immersing the substrate platform into a salt melt comprising ions to form an array of waveguides in the substrate platform through an ion diffusion process, and controlling a rate of immersion such that a diffusion depth of the ions varies as a function of a distance in a direction from the first end to the second end, wherein the array of waveguides extends in the direction from the first end to the second end.