Circular dichroism enhancement in plasmonic nanorod metamaterials.

Optical activity is a fundamental phenomenon originating from the chiral nature of crystals and molecules. While intrinsic chiroptical responses of ordinary chiral materials to circularly polarized light are relatively weak, they can be enhanced by specially tailored nanostructures. Here, nanorod metamaterials, comprising a dense array of vertically aligned gold nanorods, is shown to provide a significant enhancement of the circular dichroism response of an embedded material.

Chiroptical effects in planar achiral plasmonic oriented nanohole arrays.

Chiroptical effects are routinely observed in three dimensional objects lacking mirror symmetry or quasi-two-dimensional thin films lacking in-plane mirror symmetry. Here we show that symmetric plasmonic planar arrays of circular nanoholes produced strong chiroptical responses at visible wavelengths on tilting them with respect to the incident light beam due to the collective asymmetric nature of their surface plasmon excitations. This extrinsic chiroptical effect can be stronger than the local chiroptical response in arrays of intrinsically chiral nanoholes and may be useful for chiral sensing and negative refraction.

The size-dependent ferroelectric phase transition in BaTiO₃ nanocrystals probed by surface plasmons.

A new technique for probing the temperature dependence of the dielectric constant of ferroelectric nanocrystals (NCs) using shifts in the localized surface plasmon resonance (LSPR) wavelength of gold nanoparticles attached to the surface of the ferroelectric NCs is demonstrated. This technique can selectively probe the surface of the NCs and was used to study the ferroelectric-to-paraelectric phase transition of barium titanate (BTO) nanocubes in three size regimes of 16 ± 4, 47 ± 11, and 220 ± 140 nm. Temperature-dependent Raman spectroscopy was also applied to probe the whole volume of the NCs.