Tunable-Focusing of Surface Plasmon Polaritons With a Slightly Irregular Line of Nanofootprints

Tunable surface plasmon polariton launchers are highly demanded in various applications of nanophotonics for achieving controllable plasmonic signals coupling and multiplexing. Here, a tunable-focusing device with simplified structure is suggested. It consists of an array of nanofootprints. This device allows us polarization-controlled tunable plasmonic directing and focusing on the two-dimensional metallic surface. The simulation and experimental results indicate that the focal position of the excited plasmon field can be flexibly tuned between two distinct positions just by manipulating the incident polarization state. Hence, this nanofootprints structure can serve effectively as controllable plasmonic routers and demultiplexers. It also has promising application prospects in many other fields of optics.