Near-field flat focusing mirrors using a metallic subwavelength grating on top of a plasmonic waveguide

Flat focusing mirrors without any optical axis have been investigated by metallic nanoantennas on top of a plasmonic waveguide. The principle of flat focusing mirror is similar to Veselago flat lens, which allows the beam focusing in the near field. The key idea is to provide anomalous lateral displacement that can restrain a beam spreading and even focus a divergent beam upon reflection. The device keeps transversal invariance (lack of an optical axis) because it remains the periodic structure.