Realization of tightly confined channel plasmon polaritons at low frequencies

Subwavelength guiding of channel plasmon polaritons (CPPs) is realized by a properly structured metallic groove at frequencies far below the plasma frequency of metal. Compared with CPPs at visible frequencies, more versatile physical mechanisms can be introduced in these CPPs by surface patterning, so that they can exhibit superior features as visible CPPs, while eliminating the potential drawbacks of the latter. Such designer CPPs are explained physically with the effective-index method and verified experimentally in the microwave regime.