Polychromatic nanofocusing of surface plasmons

In this work the authors introduce the concept of polychromatic plasmonics, and demonstrate the functionalities of a broadband plasmonic lens based on metal-dielectric-metal (MDM) structures. The authors utilize quadratic variation of the dielectric layer in the transverse direction to produce a parabolic optical potential which is practically wavelength independent. Nanofocusing of this lens is demonstrated over a bandwidth exceeding an optical octave (>;500nm) thus allowing a variety of effects for polychromatic plasmon nanofocusing.