Polychromatic nanofocusing of surface plasmons

Abstract

Despite the recent achievements in the field of plasmonics, there are still several challenging obstacles for real world applications, one of which is strong wavelength dispersion. Although it is possible to focus polychromatic light asymptotically at the tip of a taper, light is fully localized there and could not propagate beyond [1]. This characteristic makes tapered structures not suitable for short pulse signal processing in an integrated photonic chip. In this work we introduce the concept of polychromatic plasmonics, and demonstrate the functionalities of a broadband plasmonic lens based on metal-dielectric- metal (MDM) structures. We 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. Show more