3D harnessing of light with 2.5D photonic crystals



It is emphasized that two-dimensional photonic crystals (2D PC) have not only a great potential for the development of 2D nanophotonics in the inplane waveguided configuration, but that they may also open the way to other brilliant developments, with an extension to out-of-plane operation, along a 2.5D nanophotonics approach. In this 2.5D approach, a 1D–2D high index contrast lateral structuration is combined with a 1D high index contrast vertical structuration, using multilayer membrane stacks including 1D–2D photonic crystal membranes, thus resulting in so-called 2.5D PC. As a specific illustration of recent achievements along this approach, new families of VCSEL structures are presented.