Customized polymer/glass diffractive waveguide stacks for augmented reality/mixed reality applications
A diffractive waveguide stack includes first, second, and third diffractive waveguides for guiding light in first, second, and third visible wavelength ranges, respectively. The first diffractive waveguide includes a first material having first refractive index at a selected wavelength and a first target refractive index at a midpoint of the first visible wavelength range. The second diffractive waveguide includes a second material having a second refractive index at the selected wavelength and a second target refractive index at a midpoint of the second visible wavelength range. The third diffractive waveguide includes a third material having a third refractive index at the selected wavelength and a third target refractive index at a midpoint of the third visible wavelength range. A difference between any two of the first target refractive index, the second target refractive index, and the third target refractive index is less than 0.005 at the selected wavelength.
1. A method of fabricating diffractive waveguides for a waveguide stack, the method comprising:
combining a first monomer and a second monomer in a first ratio to yield a first polymerizable material;
casting the first polymerizable material in a first diffractive waveguide mold and polymerizing the first polymerizable material to yield a first diffractive waveguide for guiding light in a first visible wavelength range, wherein the first diffractive waveguide has a first yellowness index and a first refractive index at a selected wavelength;
combining the first monomer and the second monomer in a second ratio to yield a second polymerizable material; and
casting the second polymerizable material in a second diffractive waveguide mold and polymerizing the second polymerizable material to yield a second diffractive waveguide for guiding light in a second visible wavelength range, wherein the second diffractive waveguide has a second yellowness index and a second refractive index at the selected wavelength,
wherein:
a wavelength in the first visible wavelength range exceeds a wavelength in the second visible wavelength range,
the first refractive index exceeds the second refractive index at the selected wavelength, and
the first yellowness index exceeds the second yellowness index at the selected wavelength.
2. The method of claim 1 , further comprising:
combining the first monomer and the second monomer in a third ratio to yield a third polymerizable material; and
casting the third polymerizable material in a third diffractive waveguide mold and polymerizing the third polymerizable material to yield a third diffractive waveguide for guiding light in a third visible wavelength range, wherein the third diffractive waveguide has a third yellowness index and a third refractive index at the selected wavelength,
wherein:
a wavelength in the second visible wavelength range exceeds a wavelength in the third visible wavelength range, and
the second yellowness index exceeds the third yellowness index at the selected wavelength.
3. The method of claim 2 , wherein the second refractive index exceeds the third refractive index at the selected wavelength.
4. The method of claim 1 , wherein the selected wavelength is 589 nm.
5. The method of claim 1 , wherein casting the first polymerizable material comprises providing the first polymerizable material to a first casting head, the second polymerizable material comprises providing the second polymerizable material to a second casting head.
6. The method of claim 5 , wherein the first casting head and the second casting head are different.
7. The method of claim 1 , wherein casting the first polymerizable material and the second polymerizable material comprises providing the first polymerizable material and the second polymerizable material to a multi-head casting system.
8. The method of claim 7 , wherein the multi-head casting system comprises a first casting head and a second casting head, and the first casting head and the second casting head are different.
9. The method of claim 1 , wherein the first ratio and the second ratio are different.
10. The method of claim 1 , further comprising selecting first conditions for polymerizing the first polymerizable material and second conditions for polymerizing the second polymerizable material yields a first combination of the first refractive index and the first yellowness index and a second combination of the second refractive index and the second yellowness index, wherein first conditions differ from the second conditions, and the first combination differs from the second combination.
11. The method of claim 1 , wherein polymerizing the first polymerizable material, the second polymerizable material, or both yields a thiol-ene or a polycarbonate.
12. The method of claim 1 , further comprising superimposing the first diffractive waveguide and the second diffractive waveguide to yield a waveguide stack.