Folded light path for planar optical devices

摘要

There is provide an optical device comprising a planar structure adapted so that light coupled into an optical layer of the device follows a folded optical path, thereby increasing the interaction length, wherein the folded optical path is substantially perpendicular to the planar structure so as to render the optical device substantially polarization insensitive. Typically, the folded path is achieved by modifying at least one of an upper surface of the optical layer and a lower surface of the optical layer such that it is no longer planar, but instead comprises one or more angled facets.