Graphene (oxide) for photonic integration

Summary form only given. A variety of photonic device functionalities has now been demonstrated using both graphene and more-or-less reduced versions of the closely related compound material, graphene oxide (GO). Graphene oxide can readily be produced with a range of degrees of oxidation - and it is then generically called reduced graphene oxide (rGO). It is also important, from various points-of-view, that rGO typically incorporates a significant amount of water (H2O). Oxygen and hydrogen atoms that are bonded onto a single sheet of graphene form branches that may be labelled chemically as carboxyl, carbonyl and hydroxyl bonds, inter alia.The functions that have been demonstrated in photonic device structures that incorporate graphene and rGO include electrooptic and all-optical modulation, photo-detection, polarization selection and light emission. These demonstrations of different device functionalities also provide indications of potentially superior performance that arise from the special properties of both graphene and rGO. Other 2D-lattice materials, e.g., molybdenum suphide and molybdenum selenide, have also been identified and offer further possibilities for device functionality. Several different planar deposition technologies have now been established and lithographic patterning processes have also been demonstrated. Processes for local modification of the 2D material properties, on various size-scales, are also possible. For use as an ingredient in photonic integration, the graphene/rGO may be deposited directly onto a suitably prepared substrate or deposited, e.g., on a thin foil of a metal such as copper - and then transferred onto another substrate. The availability of convenient deposition techniques means that graphene and GO are both of interest for planar photonic integration technology. The `substrate' to be exploited in the photonic integrated circuit (PIC) can be practically any waveguide-based integration system, e.g., silicon-on-insulator, oxide or chalcogenide type glasses, epitaxial III-V semiconductors or polymeric materials. This invited presentation will provide a targeted review of research relevant to the exploitation of graphene or GO in photonic integration. Recent and new results from our own research, which has been particularly concerned with applications of multi-layer GO, will be featured.