SLANTED GRATING FABRICATION
A method includes patterning a plurality of first trenches in a surface of a substrate; and etching the plurality of first trenches with an etchant having an etch rate for a first crystalline plane of the substrate that is greater than for a second crystalline plane of the substrate. The etching forms a slanted grating in the substrate.
1 . A method comprising:
patterning a plurality of first trenches in a surface of a substrate; and
etching the plurality of first trenches with an etchant having an etch rate for a first crystalline plane of the substrate that is greater than for a second crystalline plane of the substrate,
wherein the etching forms a slanted grating in the substrate.
2 . The method of claim 1 , wherein sidewalls of the slanted grating are defined by the second crystalline plane.
3 . The method of claim 1 , where bases of the slanted grating are defined by the second crystalline plane.
4 . The method of claim 2 , wherein the substrate has a diamond cubic crystal structure, and
wherein the second crystalline plane is a {1 1 1} plane of the diamond cubic crystal structure.
5 . (canceled)
6 . (canceled)
7 . The method of claim 4 , wherein the slanted grating is formed by a plurality of second trenches,
wherein the second trenches have a depth extending into the surface of the substrate, a width extending between two sidewalls defined by the {1 1 1} plane, and a length that is greater than the width, and
wherein the length extends parallel to a <1 1 0> direction of the diamond cubic crystal structure.
8 . (canceled)
9 . The method of claim 4 , wherein the substrate comprises a (1 1 1)-oriented substrate, and wherein the sidewalls of the slanted grating have a slant angle of about 19.5° degrees.
10 . The method of claim 4 , wherein:
(1):
a normal direction to the surface of the substrate has a first angle of 19.5°−θ° with respect to the {1 1 1} plane of the diamond cubic crystal structure,
the sidewalls of the slanted grating have a slant angle equal to the first angle, and 0°<θ°<19.5°, or
(2):
a normal direction to the surface of the substrate has a first angle of 19.5°+θ° with respect to the {1 1 1} plane of the diamond cubic crystal structure, the sidewalls of the slanted grating have a slant angle equal to the first angle, and θ°>0.
11 . (canceled)
12 . The method of claim 4 , wherein the surface of the substrate is sloped, with respect to a (1 1 1) plane of the diamond cubic crystal structure, in a <2 −1 −1> direction of the diamond cubic crystal structure.
13 . The method of claim 1 , wherein patterning the plurality of first trenches in the surface of the substrate comprises:
forming a mask on the surface of the substrate; and
anisotropically etching the substrate through openings in the mask, to form the plurality of first trenches.
14 . The method of claim 13 , wherein each trench of the plurality of first trenches has vertical sidewalls.
15 .- 16 . (canceled)
17 . The method of claim 13 , comprising:
subsequent to patterning the plurality of first trenches, and prior to etching the plurality of first trenches, removing a portion of the mask adjacent to at least one first trench of the plurality of first trenches.
18 . (canceled)
19 . The method of claim 1 , wherein the slanted grating has a pitch between 20 μm and 200 μm.
20 .- 22 . (canceled)
23 . A method comprising:
providing a master template substrate;
forming a slanted diffraction grating pattern in a surface of the master template substrate; and
using the master template substrate having the slanted diffraction grating pattern to imprint the slanted diffraction grating pattern on a device substrate.
24 . The method of claim 23 , wherein the master template substrate has a diamond cubic crystal structure, and wherein the slanted diffraction grating pattern is defined by a first {1 1 1} plane of the diamond cubic crystal structure.
25 . The method of claim 24 , comprising forming a second slanted diffraction grating pattern in the surface of the master template substrate, the second slanted diffraction grating pattern defined by a second {1 1 1} plane of the diamond cubic crystal structure, the second {1 1 1} plane different from the first {1 1 1} plane.
26 . The method of claim 23 , wherein sidewalls of the slanted diffraction grating pattern are defined by a crystalline plane of the master template substrate.
27 . The method of claim 23 , wherein the slanted diffraction grating pattern is a first slanted diffraction grating pattern, and wherein the method comprises:
forming a second slanted diffraction grating pattern in the surface of the master template substrate, wherein the first slanted diffraction grating pattern and the second slanted diffraction grating pattern have different array directions, and
using the master template substrate to imprint the second slanted diffraction grating pattern on the device substrate.
28 .- 33 . (canceled)
34 . An optical device, comprising:
a waveguide, and
a slanted grating defined in a surface of a substrate, the slanted grating arranged to direct light into the waveguide, wherein sidewalls of the slanted grating are defined by a crystalline plane of the substrate.
35 . The optical device of claim 34 , wherein the substrate has a diamond cubic crystal structure, and wherein the sidewalls are defined by a {1 1 1} plane of the diamond cubic crystal structure.
36 . The optical device of claim 34 , wherein the substrate includes the waveguide.
37 .- 40 . (canceled)