Strong spatial and spectral localization of surface plasmons in individual randomly disordered gold nanosponges

Abstract

Porous nanosponges, percolated with a three-dimensional network of 10-nm sized ligaments, recently emerged as promising substrates for plasmon-enhanced spectroscopy and (photo-)catalysis. Experimental and theoretical work suggests surface plasmon localization in some hot-spot modes as the physical origin of their unusual optical properties, but so far the existence of such hot-spots has not been proven. Here we use scattering-type scanning near-field nano-spectroscopy on individual gold nanosponges to reveal spatially and spectrally confined modes with 10 nanometer localization lengths by mapping the local optical density of states. High quality factors of individual hot-spots of more than 40 are demonstrated. A statistical analysis of near-field intensity fluctuations unveils plasmonics in the strong localization regime. The observed field localization and enhancement make such nanosponges an appealing platform for a variety of applications ranging from nonlinear optics to strong-coupling physics.

23 pages, 5 figures, submitted to Nano Letters

References in corpus (8)

• Strong coupling between surface plasmon polaritons and emitters
• Statistical Signatures of Photon Localization
• Fluctuations of the local density of states probe localized surface plasmons on disordered metal films
• Transport through modes in random media
• Intensity Distribution of Waves Transmitted Through a Multiple Scattering Medium
• Strong Coupling to Two-Dimensional Anderson Localized Modes
• Regularized quasinormal modes for plasmonic resonators and open cavities
• Distance dependence of the local density of states in the near field of a disordered plasmonic film

Cited by in corpus (2)

• Dry synthesis of bi-layer nanoporous metal films as plasmonic metamaterial
• Exceptional broadband absorption of nanoporous gold explained by plasmonic resonances at dangling ligaments