DYNAMICALLY ACTUABLE DIFFRACTIVE OPTICAL ELEMENT
A dynamic diffractive structure includes an optical waveguide having a surface, a first transparent electrode coupled to the surface, a chamber formed on the surface, and a nanoscale diffraction grating structure including a plurality of ridges formed on the first transparent electrode and within the chamber and a plurality of channels between adjacent ridges of the plurality of ridges. The dynamic diffractive structure also includes a fluid having an index of refraction disposed within the chamber, a second transparent electrode, and a cover coupled to the chamber. In a first state, the fluid substantially fills the plurality of channels, causing the dynamically actuable diffractive grating to be in an “off” state and in a second state, the fluid is substantially absent from at least a portion of the plurality of channels, causing the dynamically actuable diffractive grating to be in an “on” state and diffract incident light.
1 . A dynamically actuable diffractive grating comprising:
an optical waveguide having a surface;
a first transparent electrode coupled to the surface of the optical waveguide;
a chamber formed on the surface of the optical waveguide;
a nanoscale diffraction grating structure including a plurality of ridges formed on the first transparent electrode and within the chamber and a plurality of channels between adjacent ridges of the plurality of ridges, wherein the plurality of channels are arranged as a periodic array;
a fluid having an index of refraction disposed within the chamber;
a second transparent electrode disposed opposite the first transparent electrode, wherein the first transparent electrode and the second transparent electrode are configured to receive an electric potential therebetween; and
a cover coupled to the chamber;
wherein, in a first state, the fluid substantially fills the plurality of channels, causing the dynamically actuable diffractive grating to be in an “off” state; and
wherein, in a second state, the fluid is substantially absent from at least a portion of the plurality of channels, causing the dynamically actuable diffractive grating to be in an “on” state and diffract incident light.
2 . The dynamically actuable diffractive grating of claim 1 wherein the first transparent electrode is below the nanoscale diffraction grating structure and the second transparent electrode is on top of the nanoscale diffraction grating structure.
3 . The dynamically actuable diffractive grating of claim 1 wherein the fluid comprises a polar fluid including water or an electrolytic solution.
4 . The dynamically actuable diffractive grating of claim 1 wherein the chamber comprises silicon dioxide.
5 . The dynamically actuable diffractive grating of claim 1 wherein the nanoscale diffraction grating structure comprises silicon dioxide.
6 . The dynamically actuable diffractive grating of claim 1 wherein the index of refraction of the fluid substantially matches an index of refraction of the ridges of the plurality of ridges.
7 . The dynamically actuable diffractive grating of claim 1 wherein the first transparent electrode or the second transparent electrode comprise indium tin oxide (ITO) or graphene.
8 . The dynamically actuable diffractive grating of claim 1 wherein the optical waveguide comprises sapphire or a dielectric material.
9 . The dynamically actuable diffractive grating of claim 1 wherein the cover is configured to seal the plurality of channels.
10 . The dynamically actuable diffractive grating of claim 1 wherein the plurality of ridges have a width less than 200 nanometers.
11 . The dynamically actuable diffractive grating of claim 1 wherein movement of the fluid within the plurality of channels is effected by electroosmosis in response to the electric potential.
12 . The dynamically actuable diffractive grating of claim 1 wherein the fluid is immiscible with a second fluid disposed adjacent to the plurality of channels.
13 . The dynamically actuable diffractive grating of claim 1 wherein at least the surface of the optical waveguide, the first transparent electrode, or the second transparent electrode are chemically treated to enhance wetting properties for the fluid.
14 . The dynamically actuable diffractive grating of claim 1 wherein the second transparent electrode is hydrophobic.
15 . The dynamically actuable diffractive grating of claim 1 wherein a periodicity of the periodic array is dynamically variable by selective control of the electric potential to individual channels of the plurality of channels or groups of channels of the plurality of channels.
16 . The dynamically actuable diffractive grating of claim 1 wherein the optical waveguide is configured to receive imagewise modulated light.
17 . The dynamically actuable diffractive grating of claim 1 wherein the dynamically actuable diffractive grating comprises an element of an augmented reality or virtual reality eyepiece.
18 . The dynamically actuable diffractive grating of claim 1 wherein the electric potential applied between the first transparent electrode and the second transparent electrode is less than 10 volts.
19 . The dynamically actuable diffractive grating of claim 1 further comprising a plurality of fluid reservoirs in fluid communication with the plurality of channels.
20 . The dynamically actuable diffractive grating of claim 1 wherein the plurality of ridges comprise positive or negative surface relief pattern diffractive lenses.