Granted Patent B2

US 12,596,229 · App. 18/228,623 · Granted Apr 7, 2026

Inventors: Tzu-Han Chang (West Lafayette, IN); Chen-Lung Hung (Zionsville, IN)

Assignee: Purdue Research Foundation

G02B6/1228G02B6/13

Abstract

Claims (24)

1 . 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 three-dimensional tapered indentation into a top surface of the resist material layer, wherein the three-dimensional tapered indentation defines 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) transferring the three-dimensional tapered indentation from the resist material layer to the waveguide material layer using plasma etching;

(c) forming a three-dimensional tapered optical waveguide by removing a portion of the waveguide material layer adjacent to the three-dimensional tapered indentation; and

(d) depositing a second cladding material layer over the 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.

2 . The method of claim 1 , wherein forming a three-dimensional tapered indentation into a top surface of the resist material layer includes:

(i) forming a series of staircase structures into the top surface of the resist material layer, wherein each surface of each staircase structure that extends into the resist material layer in a direction perpendicular to the top surface of the resist material layer defines a sloped surface, and

(ii) thermally smoothing the series of staircase structures into a continuous slope between the first end and the second end.

3 . The method of claim 1 , further comprising trimming the first and the second cladding layers to form a rectangular cladding structure surrounding the optical waveguide to therefore modify a guided mode profile of the optical waveguide.

4 . The method of claim 3 , wherein trimming the first and the second cladding layers includes performing a third lithography procedure and at least one of a second etching procedure or a cleaving procedure.

5 . The method of claim 4 , further comprising cleaving the first and second cladding layers to form the optical input facet.

6 . 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.

7 . The method of claim 6 , wherein each surface of each staircase structure that extends into the resist material layer in a direction perpendicular to the top surface of the resist material layer defines a sloped surface.

8 . The method of claim 6 , further comprising trimming at least one of the first cladding material layer or the second cladding material layer to form the optical input facet to therefore modify a guided mode profile of the optical waveguide.

9 . 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.

10 . The optical waveguide of claim 9 , wherein the optical cladding material is formed into a rectangular shape having equal height and width.

Assignments (1)

Continuity (2)

References Cited (105)