Spherical arrangements of metallic nanoparticles, defined as core–shell nanoclusters, have obtained intense interest in the metamaterials community as they have highly tunable optical properties [1]. It has been proposed... [ view full abstract ]
Spherical arrangements of metallic nanoparticles, defined as core–shell nanoclusters, have obtained intense interest in the metamaterials community as they have highly tunable optical properties [1]. It has been proposed that they allow advancements towards materials with double negative properties [2]. Furthermore, they exhibit a strong isotropic magnetic response [3]. The fabrication of these structures is flexible with the possibility to tune the architecture and consequently the optical properties. The key ingredients to achieve such materials are meta-atoms. Other forms such as nanorods provide considerable advantages over the more basic spherical particles due to the introduction of anisotropy, the enhanced extinction coefficients and the wide range of tunability of the longitudinal plasmon resonance. Metal nanoparticles with anisotropic shape have various interesting optical properties, for the reason that the surface plasmon resonance bands split up for orientations along major and minor axes. Moreover, anisotropic metal particles show enhanced nonlinear response [4] when compared to spherically shaped particles, and may thus be used as building blocks in a variety of optical devices. Using bottom-up technique, three-dimensional plasmonic nanostructures were synthesized and characterized. Such structures are sufficiently small to be perceived as an individual object in the far field and exhibit strong and isotropic magnetic response in the visible spectral domain.
References
[1] Shalaev, V.M., Optical negative-index metamaterials. Nat. Photonics 1, 41(2006).
[2] C.R. Simovski, S.A. Tretyakov, Model of isotropic resonant magnetism in the visible range based on core–shell clusters. Phys. Rev. B79(4), 045111 (2009).
[3] S. Mühlig et al., Self-assembled plasmonic core–shell clusters with an isotropic magnetic dipole response in the visible range. ACS Nano5(8), 6586–6592 (2011).
[4] K. P. Yuen, M. F. Law, K. W. Yu, P. Sheng, Optical nonlinearity enhancement via geometric anisotropy. Phys. Rev. E56, 1322 (1997).
Photonic & plasmonic nanomaterials , Optical properties of nanostructures , Metamaterials
