Optical element stack assemblies
The present disclosure describes optical element stack assemblies that include multiple substrates stacked one over another. At least one of the substrates includes an optical element, such as a DOE, on its surface. The stack assemblies can be fabricated, for example, in wafer-level processes.
1. A wafer-level method of fabricating a plurality of stack assemblies, the method comprising:
providing first and second wafers, wherein each of the first wafer and the second wafer has a plurality of optical elements on its surface;
forming through-holes in the second wafer;
using a single vacuum injection technique to form vacuum injection molded pieces which each include an upper and a lower spacer on opposite surfaces of the second wafer, and a part which fills a through-hole in the second wafer with a same material that forms the upper and lower spacers;
attaching the first wafer to the second wafer to form a wafer stack, the first and second wafers being attached such that each optical element is disposed between the first and second wafers, wherein the first and second wafers are attached to one another through adhesive disposed between lateral side portions of the optical elements of the first wafer and the optical elements on the second wafer; and
separating the wafer stack into a plurality of stack assemblies, each of which includes at least two of the optical elements.
2. The method of claim 1 wherein the optical elements are diffractive optical elements.
3. The method of claim 1 wherein the optical elements are replicated optical elements.