Diffractive optical elements with mitigation of rebounce-induced light loss and related systems and methods
Display devices include waveguides with in-coupling optical elements that mitigate re-bounce of in-coupled light to improve overall in-coupling efficiency and/or uniformity. A waveguide receives light from a light source and/or projection optics and includes an in-coupling optical element that in-couples the received light to propagate by total internal reflection in a propagation direction within the waveguide. Once in-coupled into the waveguide the light may undergo re-bounce, in which the light reflects off a waveguide surface and, after the reflection, strikes the in-coupling optical element. Upon striking the in-coupling optical element, the light may be partially absorbed and/or out-coupled by the optical element, thereby effectively reducing the amount of in-coupled light propagating through the waveguide. The in-coupling optical element can be truncated or have reduced diffraction efficiency along the propagation direction to reduce the occurrence of light loss due to re-bounce of in-coupled light, resulting in less in-coupled light being prematurely out-coupled and/or absorbed during subsequent interactions with the in-coupling optical element.
1. An optical device comprising;
a first waveguide comprising a reflective diffractive optical element, the reflective diffractive optical element comprising:
protrusions on a surface of the first waveguide;
an interface layer on the protrusions; and
a reflective layer on the interface layer,
wherein the interface layer and the reflective layer are conformal to the protrusions.
2. The optical device of claim 1 , wherein the interface layer comprises one or more of a plasma-treated surface, a surfactant layer, and a catalyst.
3. The optical device of claim 2 , wherein the catalyst comprises one more of tin or palladium-containing compounds.
4. The optical device of claim 1 , wherein the reflective layer is at least 95% metal.
5. The optical device of claim 1 , wherein the reflective layer is substantially free of pinholes.
6. The optical device of claim 1 , wherein the reflective diffractive optical element is an in-coupling optical element configured to redirect incident light at angles such that the light propagates through the first waveguide by total internal reflection.
7. The optical device of claim 6 , wherein the reflective layer reflects the incident light with a reflectivity of at least 85%.
8. The optical device of claim 1 , further comprising a second waveguide and a third waveguide, wherein the second waveguide is configured to output light of a different range of wavelengths than the third waveguide,
wherein each of the first, second, and third waveguides comprises a reflective diffractive optical element comprising:
protrusions on a surface of the first waveguide;
an interface layer on the protrusions; and
a reflective layer on the interface layer.
9. The optical device of claim 1 , wherein the surface comprises a wall that defines a boundary of the reflective layer.
10. The optical device of claim 9 , wherein the wall comprises a mechanical spacer configured to maintain space between the first waveguide and an other waveguide.
11. The optical device of claim 1 , wherein the optical device is a display system comprising a spatial light modulator, wherein the spatial light modulator is configured to output light containing image information onto the reflective diffractive optical element.
12. The optical device of claim 1 , further comprising a capping layer on the reflective layer.