Controlling etch angles by substrate rotation in angled etch tools

An optical device, comprising:

• a layer of grating material disposed over the substrate;
• a first portion of one or more first gratings disposed in the layer of grating material over the substrate, each first grating of the first portion comprising:
• a first slant angle ϑ′1 formed at a first rotation angle φ1, wherein the first rotation angle φ1 is between an etch angle t and a first grating vector;
• and
• the first grating vector wherein the first grating vector is a first orientation of each first grating relative to an origin of the substrate defined by the first slant angle ϑ′1;
• and
• a second portion of one or more second gratings disposed in the layer of grating material over the substrate, each second grating of the second portion comprising:
• a second slant angle ϑ′2, the second slant angle ϑ′2 different than the first slant angle ϑ′1, wherein the second slant angle ϑ′2 is formed at a second rotation angle φ2, wherein the second rotation angle φ2 is between the etch angle ϑ and a second grating vector;
• and
• the second grating vector, the second grating vector different than the first grating vector, wherein the second grating vector is a second orientation of the second grating relative to the origin of the substrate defined by the second slant angle, the first rotation angle φ1 and the second rotation angle φ2 are selected by a system of equations ϑ=arctan(tan(ϑ′1)/cos(φ1), ϑ=arctan(tan(ϑ′2)/cos(φ2)), and Δφ=φ2−φ1.

An optical device, comprising:

• a first portion of one or more first gratings disposed on a substrate, each first grating of the first portion comprising:
• a first grating vector;
• and
• a first slant angle ϑ′1;
• and
• a second portion of one or more second gratings disposed on the substrate, each second grating of the second portion comprising:
• a second grating vector, the second grating vector different than the first grating vector;
• and
• a second slant angle ϑ′2, the second slant angle ϑ′2 different than the first slant angle ϑ′1;
• wherein the optical device is formed by a process comprising:
• projecting an ion beam to the substrate having a grating material disposed thereon, the ion beam configured to contact the grating material at ion beam angle ϑ relative to a surface normal of the substrate, wherein:
• the first portion of the substrate is positioned at a first rotation angle φ1 between the ion beam and the first grating vector of one or more first gratings to be formed by the ion beam contacting the grating material of the first portion;
• the first rotation angle φ1 is selected to form the one or more first gratings with the first slant angle ϑ′1 relative to the surface normal of the substrate;
• the second portion of the substrate is positioned at a second rotation angle φ2 between the ion beam and the second grating vector of one or more second gratings to be formed by the ion beam contacting the grating material;
• and
• the second rotation angle φ2 is selected to form the one or more second gratings with the second slant angle ϑ′2 relative to the surface normal of the substrate, at least one of the first slant angle ϑ′1 and the second slant angle ϑ′2 are different than the ion beam angle t, wherein the first rotation angle φ1 and the second rotation angle φ2 are selected by a system of equations ϑ=arctan(tan(ϑ′1)/cos(φ1)), ϑ=arctan(tan(ϑ′2)/cos(φ2)), and Δφ=φ2−φ1.