Optically Transparent and Flexible Graphene Reciprocal and Nonreciprocal Microwave Planar Components

The sheet resistance of graphene has been recently reduced below the level of previous optically transparent conductive materials, making graphene, with its additional advantage of mechanical flexibility, the best candidate for future transparent electronics. We investigate here the viability of microwave planar components using graphene sheets as conductors towards optically transparent and flexible radio systems. Specifically, we study the waveguiding and nonreciprocal properties of such components, through the arbitrary example of a coplanar waveguide (CPW) structure, using the 2-D finite difference frequency domain (FDFD) technique. It is shown that reciprocal graphene-based components of acceptably low loss levels are achievable using graphene sheets of the lowest available resistivity, while nonreciprocal components with graphene conductors still exhibit prohibitive loss due to a fundamental trade-off between nonreciprocity and carrier density in graphene.