3D tapered nanophotonic waveguide to fiber edge coupler

A method of forming an optical waveguide from a multilayer material, wherein the multi-layer material includes a resist material layer deposited over a waveguide material layer, and the waveguide material layer deposited over a first cladding material layer, the method comprising:

• (a) using a grayscale electron-beam lithography procedure defining a spatially varying exposure dose profile in a positive polymethyl methacrylate (PMMA) resist material to form a series of staircase structures into a top surface of the resist material layer, wherein the series of staircase structures define a length separated by a first end having a first depth and a second end having a second depth, wherein the first depth is greater than the second depth;
• (b) thermally smoothing the series of staircase structures into a tapered indentation between the first end and the second end;
• (c) transferring the tapered indentation from the resist material layer to the waveguide material layer using plasma etching;
• (d) removing a portion of the waveguide material layer adjacent to the tapered indentation thereby forming a three-dimensional optical waveguide defined from the tapered indentation;
• and
• (e) depositing a second cladding material layer over the three-dimensional optical waveguide to form an optical coupler having an optical input facet, wherein depositing the second cladding material layer over the optical waveguide includes performing at least one of a plasma-enhanced chemical vapor deposition (PECVD) procedure, a low-pressure chemical vapor deposition (LPCVD) procedure, or a high-density plasma chemical vapor deposition (HDPCVD) procedure.

An optical waveguide, comprising:

• (a) an optical cladding material;
• and
• (b) a three-dimensional (3D) optical waveguide positioned inside the optical cladding material, wherein the 3D optical waveguide includes a first end defining a first cross-sectional area and a second end defining a second cross-sectional area, wherein the first cross-sectional area is less than the second cross-sectional area thereby forming a tapered length spanning between the first end and the second end, wherein the first end defines an optical input, wherein the 3D optical waveguide is fabricated by a process including forming a three-dimensional tapered indentation in a positive polymethyl methacrylate (PMMA) resist material by grayscale electron-beam lithography and transferring the indentation to a waveguide material layer using plasma etching;
• wherein the optical cladding material is formed by performing at least one of a plasma-enhanced chemical vapor deposition (PECVD) procedure, a low-pressure chemical vapor deposition (LPCVD) procedure, or a high-density plasma chemical vapor deposition (HDPCVD) procedure.