Coherent excitation-selective spectroscopy in planar metamaterials

We demonstrated that the electric and magnetic resonances of metamaterials can be separately switches off and on by positioning the metamaterials along a standing wave, while both resonances are present in travelling-wave spectra

A combinatorial approach to metamaterials discovery

Some fifteen years ago a paper reporting a combinatorial approach to materials discoveries revolutionized materials research and other disciplines such as chemistry and pharmacology [1]. Here we report on how a combinatorial approach combined with advanced nanofabrication helps to discover photonic metamaterials optimized for prescribed functionalities

Dynamic critical behavior of the classical anisotropic BCC Heisenberg antiferromagnet

Using a recently implemented integration method [Krech et. al.] based on an iterative second-order Suzuki-Trotter decomposition scheme, we have performed spin dynamics simulations to study the critical dynamics of the BCC Heisenberg antiferromagnet with uniaxial anisotropy. This technique allowed us to probe the narrow asymptotic critical region of the model and estimate the dynamic critical exponent $z=2.25 \pm 0.08$. Comparisons with competing theories and experimental results are presented.Comment: Latex, 3 pages, 5 figure

A combinatorial approach to metamaterials discovery

We report a high throughput combinatorial approach to photonic metamaterial optimization. The new approach is based on parallel synthesis and subsequent optical characterization of large numbers of spatially addressable nanofabricated metamaterial samples (libraries) with quasi-continuous variation of design parameters under real manufacturing conditions. We illustrate this method for Fano-resonance plasmonic nanostructures, arriving at explicit recipes for high quality factors needed for switching and sensing applications

A new type of optical activity in a toroidal metamaterial

We demonstrate experimentally and numerically the first ever observation of optical activity in a chiral metamaterial that is underpinned by the exotic resonant combination of an electric quadrupole and the elusive toroidal dipole

Toroidal circular dichroism

We demonstrate that the induced toroidal dipole, represented by currents flowing on the surface of a torus, makes a distinct and indispensable contribution to circular dichroism. We show that toroidal circular dichroism supplements the well-known mechanism involving electric dipole and magnetic dipole transitions. We illustrate this with rigorous analysis of the experimentally measured, polarization-sensitive transmission spectra of an artificial metamaterial, constructed from elements of toroidal symmetry. We argue that toroidal circular dichroism shall be found in large biomolecules with elements of toroidal symmetry and should be taken into account in the interpretation of circular dichroism spectra of organics

Tunable plasmonic luminescence in reconfigurable metamaterials

We show that new intense luminescence lines associated with transitions from collective plasmonic states below the Fermi level can be artificially created by metamaterial nanostructuring of plasmonic metals and tuned by nanoscale reconfiguration of metamaterial. We report on the experimental demonstration of a new radiation phenomenon on the nanoscale and its engineering into a reconfigurable metadevice: luminescence emission lines within the Fermi sea can be created by nanopatterning metal surfaces and controlled by external electrical inputs. Luminescence emission lines are associated with the decay of plasmonic excitation and are spectrally linked to the plasmonic absorption lines. Wavelength, polarization and intensity of metallic luminescence can be flexibly and independently adjusted by tweaking the geometric parameters of the metamaterial design similar to the way nanostructuring helps engineering semiconductor multiple quantum well and quantum dot luminescence

Tuning chirality in photonic metamaterials with semiconductor quantum dots

Recently we have shown that the classical phenomenon of optical activity, which is traditionally associated with chirality (helicity) of organic molecules, proteins and inorganic structures, can be observed in artificial planar media which exhibit neither 3D nor 2D chirality and called this effect "extrinsic chirality", see Fig. 1 (a) and (b). Here chirality is derived from the mutual orientation of the light beam and the metamaterial array. We observed the effect in the microwave part of the spectrum at oblique incidence to regular arrays of non-chiral subwavelength meta-molecules in form of strong circular dichroism and birefringence indistinguishable from those of chiral three-dimensional media

Spin-dynamics simulations of the triangular antiferromagnetic XY model

Using Monte Carlo and spin-dynamics methods, we have investigated the dynamic behavior of the classical, antiferromagnetic XY model on a triangular lattice with linear sizes $L \leq 300$. The temporal evolutions of spin configurations were obtained by solving numerically the coupled equations of motion for each spin using fourth-order Suzuki-Trotter decompositions of exponential operators. From space- and time-displaced spin-spin correlation functions and their space-time Fourier transforms we obtained the dynamic structure factor $S({\bf q},w)$ for momentum ${\bf q}$ and frequency $\omega$. Below $T_{KT}$(Kosterlitz-Thouless transition), both the in-plane ($S^{xx}$) and the out-of-plane ($S^{zz}$) components of $S({\bf q},\omega)$ exhibit very strong and sharp spin-wave peaks. Well above $T_{KT}$, $S^{xx}$ and $S^{zz}$ apparently display a central peak, and spin-wave signatures are still seen in $S^{zz}$. In addition, we also observed an almost dispersionless domain-wall peak at high $\omega$ below $T_{c}$(Ising transition), where long-range order appears in the staggered chirality. Above $T_{c}$, the domain-wall peak disappears for all $q$. The lineshape of these peaks is captured reasonably well by a Lorentzian form. Using a dynamic finite-size scaling theory, we determined the dynamic critical exponent $z$ = 1.002(3). We found that our results demonstrate the consistency of the dynamic finite-size scaling theory for the characteristic frequeny $\omega_{m}$ and the dynamic structure factor $S({\bf q},\omega)$ itself.Comment: 8 pages, RevTex, 10 figures, submitted to PR

Metadevice of three dimensional split ring resonators

Split-ring resonator (SRR), a kind of building block for metamaterial unit cell, has attracted wide attentions due to the resonance excitation of electric and magnetic dipolar response. Here, different from prior published lectures, fundamental plasmon properties and potential applications in novel three dimensional vertical split-ring resonators (VSRRs ) are designed and investigated. The resonant properties arose from the electric and magnetic interactions between the VSRR s and light are firstly theoretically and experimentally studied (Fig. 1(a)). Tuning the configuration of VSRR unit cells is able to generate various novel coupling phenomena in VSRRs, such as plasmon hybridization and Fano resonance, as shown in Figs. 1(b) and 1(c) . Subsequently, the VSRR-based refractive-index sensor will be demonstrated. Due to the unique structural configuration, the enhanced plasmon fields localized in VSRR gaps can be lifted off from the dielectric substrate, allowing for the increase of sensing volume and enhancing the sensitivity (Fig. 1(d)) . We further perform a VSRR based metasurface for light manipulation in optical communication frequency, as shown in Fig. 1(e). Moreover, isotropic VSRRs are approached by optimizing the structural arrangement within a unit cell (Fig. 1(f)). Figure 1(g) shows the schematic for isotropic VSRR-based perfect absorber. By incorporating a metallic mirror with isotropic VSRRs, a stronger field confinement happens to enhance the absorption ability, benefitting the development of refractive index sensor. Finally, a transverse toroidal moment generated by normal incident optical wave at gold dumbbell-shaped aperture and a VSRR is designed and experimentally demonstrated , as shown in Fig. 1(h)