“…Moreover, graphene can be smoothly modulated between electron and hole conduction, thus it is possible to create junctions between regions of opposite polarity. Thanks to this flexible control of the carrier density, electrostatically defined optical elements such as lenses [1][2][3][4][5], collimators [6,7], Fabry-Pérot [8][9][10] and Mach-Zehnder interferometers [11,12] or microcavities [13][14][15][16][17] are realizable in graphene and have been widely explored both theoretically and experimentally. Furthermore, unlike photons, carriers in graphene are charged, which opens up opportunities for applications beyond the regular optics, including manipulation with external magnetic field for transverse magnetic focusing [18][19][20] or Aharonov-Bohm effect [21][22][23].…”