The role of short and long range surface plasmons for plasmonic focusing applications

We propose and analyze a new plasmonic lens allowing the simultaneous focusing of both short and long range surface plasmons polaritons. The considered geometry is circularly symmetric and the SPP excitation is radially polarized. The long range and the short range modes are compared and found to have very different focusing properties. The trade-offs between the modes are discussed. The interplay between these two modes is used to demonstrate a practical focusing scenario providing a smaller spot size compared with previous version of plasmonic lenses, and a large depth of focus simultaneously.