Fabrication of photonic crystal structures by focused ion beam etching

Two methods for focused ion beam (FIB) etching of photonic crystal are presented. The first is a FIB-alone approach which is a very rapid, maskless process. This method has the disadvantage that it produces poor sidewall verticality, which leads to high losses in slab waveguide based systems. A second approach uses FIB to etch a metal mask layer, this is followed by reactive ion etching (RIE) of a SiO₂ layer and a final inductively coupled plasma (ICP) etch of the InP layer. Results show much improved sidewall verticality.