Method to improve display efficiency and uniformity of AR waveguide
Embodiments of the present disclosure generally relate to methods of modifying and engineering the effective thickness of an optical device substrate. The methods provide for depositing a material that is index-matched to the substrate to alter a thickness distribution of the optical device. By adjusting the thickness distribution, the optical path of light is modulated to direct the light to the output coupling grating.
1 . A method of forming a design thickness distribution in an optical device, comprising:
measuring a substrate thickness distribution of a substrate defined by a distance between a top surface of the substrate and a bottom surface of the substrate along a first length parallel to the top surface and a second length perpendicular to the first length;
generating a phase map from the substrate thickness distribution across the bottom surface of the substrate;
measuring a non-uniformity of pitch between adjacent optical device structures of a plurality of optical device structures disposed on the top surface of the substrate;
generating an engineered phase profile by subtracting the phase map and the non-uniformity of pitch from a design phase map corresponding to a phase to be formed at each location of the optical device;
converting the engineered phase profile to an engineered thickness distribution; and
disposing an index-matched layer on the bottom surface of the substrate to have the engineered thickness distribution to form a design thickness distribution, wherein the design thickness distribution is defined by the engineered thickness distribution and the substrate thickness distribution, wherein the design thickness distribution varies along the first length and the second length.
2 . The method of claim 1 , wherein the index-matched layer is disposed via an inkjet printing process to have the engineered thickness distribution.
3 . The method of claim 1 , wherein the substrate has a first refractive index and the index-matched layer has a second refractive index, wherein the second refractive index substantially matches the first refractive index.
4 . The method of claim 1 , further comprising removing an anti-reflective layer from the bottom surface of the substrate before disposing the index-matched layer.
5 . The method of claim 4 , further comprising disposing the anti-reflective layer over an exterior surface of the index-matched layer via an ALD process.
6 . The method of claim 4 , wherein the anti-reflective layer includes two or multiple stacked layers of material.
7 . The method of claim 4 , wherein the anti-reflective layer includes an alternating low index layer and high index layer, wherein the low index layer has a refractive index of between about 1.4 and about 1.7 and the high index layer has a refractive index of greater than about 2.0.