Universal switching of plasmonic signals using optical resonator modes

We propose and investigate,both experimentally and theoretically,a novel mechanism for switching and modulating plasmonic signals based on a Fano interference process,which arises from the coupling between a narrow-band optical Fabry–Pérot cavity and a surface plasmon polariton(SPP)source.The SPP wave emitted from the cavity is actively modulated in the vicinity of the cavity resonances by altering the cavity Q-factor and/or resonant frequencies.We experimentally demonstrate dynamic SPP modulation both by mechanical control of the cavity length and all-optically by harnessing the ultrafast nonlinearity of the Au mirrors that form the cavity.An electro-optical modulation scheme is also proposed and numerically illustrated.Dynamic operation of the switch via mechanical means yields a modulation in the SPP coupling efficiency of~80%,while the all-optical control provides an ultrafast modulation with an efficiency of 30%at a rate of~0.6 THz.The experimental observations are supported by both analytical and numerical calculations of the mechanical,all-optical and electro-optical modulation methods.

Repulsion of polarised particles from anisotropic materials with a near-zero permittivity component

Reduction of adhesion and stiction is crucial for robust operation on nanomechanical and optofluidic devices as well as atom and molecule behaviour near surfaces.It can be achieved using electric charging,magnetic materials or light pressure and optical trapping.Here we show that a particle scattering or emitting in close proximity to an anisotropic substrate can experience a repulsive force if one of the diagonal components of the permittivity tensor is close to zero.We derive an analytic condition for the existence of such repulsive force depending on the optical properties of the substrate.We also demonstrate the effect using realistic anisotropic metamaterial implementations of a substrate.The anisotropic metamaterial approach using metal–dielectric and graphene–dielectric multilayers provides a tuneable spectral range and a very broad bandwidth of electromagnetic repulsion forces,in contrast to isotropic substrates.

Spontaneous emission in non-local materials

Light–matter interactions can be strongly modified by the surrounding environment.Here,we report on the first experimental observation of molecular spontaneous emission inside a highly non-local metamaterial based on a plasmonic nanorod assembly.We show that the emission process is dominated not only by the topology of its local effective medium dispersion,but also by the non-local response of the composite,so that metamaterials with different geometric parameters but the same local effective medium properties exhibit different Purcell factors.A record-high enhancement of a decay rate is observed,in agreement with the developed quantitative description of the Purcell effect in a non-local medium.An engineered material non-locality introduces an additional degree of freedom into quantum electrodynamics,enabling new applications in quantum information processing,photochemistry,imaging and sensing with macroscopic composites.