New Twists of 3D Chiral Metamaterials Fernandez‐Corbaton, I.; Rockstuhl, C.; Ziemke, P. ...
Advanced materials,
06/2019, Letnik:
31, Številka:
26
Journal Article
Recenzirano
Odprti dostop
Rationally designed artificial materials, called metamaterials, allow for tailoring effective material properties beyond (“meta”) the properties of their bulk ingredient materials. This statement is ...especially true for chiral metamaterials, as unlocking certain degrees of freedom necessarily requires broken centrosymmetry. While the field of chiral electromagnetic/optical metamaterials has become rather mature, the field of elastic/mechanical metamaterials is just emerging and wide open. This research news reviews recent theoretical and experimental progress concerning 3D chiral mechanical and optical metamaterials, with special emphasis on work performed at KIT.
Chiral optical and mechanical 3D rationally designed artificial materials, called metamaterials, give access to new effective material degrees of freedom. The similarities and differences between optics and mechanics in regard to chiral continuum descriptions and the experimental and theoretical status of the two subfields are reviewed. Furthermore, future perspectives and potential applications are outlined.
We experimentally demonstrate a three-dimensional chiral optical metamaterial that exhibits an asymmetric transmission for forwardly and backwardly propagating linearly polarized light. The ...observation of this novel effect requires a metamaterial composed of three-dimensional chiral meta-atoms without any rotational symmetry. Our analysis is supported by a systematic investigation of the transmission matrices for arbitrarily complex, generally lossy media that allows deriving a simple criterion for asymmetric transmission in an arbitrary polarization base. Contrary to physical intuition, in general the polarization eigenstates in such three-dimensional and low-symmetry metamaterials do not obey fixed relations and the associated transmission matrices cannot be symmetrized.
We explore the optical properties of a meta-atom made of plasmonic nanopatches that possess an increasing degree of complexity. We show that if two nanopatches are strongly coupled and have a ...different geometrical footprint, the meta-atom exhibits a resonant magnetoelectric response, in addition to the anticipated resonant electric and magnetic response. Thus, it behaves similarly as the so-called omega particle, but with the unique advantage that frequency and strength of this magnetoelectric resonance can be independently tuned and modified with respect to the corresponding values of the electric resonance. This allows a metasurface of such meta-atoms to possess widely controlled reflection and transmission coefficients, e.g., the regimes of strongly asymmetric reflectance and perfect absorption become possible. Alternatively, an individual meta-atom of such kind can act as a directive nanoantenna with zero backscattered fields (Huygens' scatterer).
Unitary transformations are routinely modeled and implemented in the field of quantum optics. In contrast, nonunitary transformations, which can involve loss and gain, require a different approach. ...In this work, we present a universal method to deal with nonunitary networks. An input to the method is an arbitrary linear transformation matrix of optical modes that does not need to adhere to bosonic commutation relations. The method constructs a transformation that includes the network of interest and accounts for full quantum optical effects related to loss and gain. Furthermore, through a decomposition in terms of simple building blocks, it provides a step-by-step implementation recipe, in a manner similar to the decomposition by Reck et al. Experimental Realization of Any Discrete Unitary Operator, Phys. Rev. Lett. 73, 58 (1994) but applicable to nonunitary transformations. Applications of the method include the implementation of positive-operator-valued measures and the design of probabilistic optical quantum information protocols.
Light interaction with disordered materials is both complex and fascinating at the same time. Here, we reveal disorder-induced phase transitions in a dielectric Huygens' metasurface made from silicon ...nanocylinders that simultaneously support an electric and magnetic dipole resonance. Depending on the degree of positional disorder and the spectral detuning of the two resonances, the phase angle of the transmission coefficient exhibits a clear phase transition from normal to anomalous dispersion. Combined with the considerations of whether the resonances of spectrally detuned particles appear as separated or overlapping, we distinguish four different phase states. We study this phenomenon analytically by employing dipole particles and disclose the entire phase diagram, support our insights with full-wave simulations of actual structures, and corroborate the findings with experimental results. Unveiling this phenomenon is a milestone simultaneously in the growing fields of metamaterial-inspired silicon nanophotonics, photonics in disordered media, and the fundamental physics of phase transitions.
The combination of modern nanofabrication techniques and advanced computational tools has opened unprecedented opportunities to mold the flow of light. In particular, discrete photonic structures can ...be designed such that the resulting light dynamics mimics quantum mechanical condensed matter phenomena. By mapping the time-dependent probability distribution of an electronic wave packet to the spatial light intensity distribution in the corresponding photonic structure, the quantum mechanical evolution can be visualized directly in a coherent, yet classical wave environment. On the basis of this approach, several groups have recently observed discrete diffraction, Bloch oscillations and Zener tunnelling in different dielectric structures. Here we report the experimental observation of discrete diffraction and Bloch oscillations of surface plasmon polaritons in evanescently coupled plasmonic waveguide arrays. The effective external potential is tailored by introducing an appropriate transverse index gradient during nanofabrication of the arrays. Our experimental results are in excellent agreement with numerical calculations.
Using rigorous diffraction theory we investigate the scattering properties of various random textures currently used for photon management in thin-film solar cells. We relate the haze and the ...angularly resolved scattering function of these cells to the enhancement of light absorption. A simple criterion is derived that provides an explanation why certain textures operate more beneficially than others. Using this criterion we propose a generic surface profile that outperforms the available substrates. This work facilitates the understanding of the effect of randomly textured surfaces and provides guidelines towards their optimization.
We map in real space and by purely optical means near-field optical information of localized surface plasmon polariton (LSPP) resonances excited in nanoscopic particles. We demonstrate that careful ...polarization control enables apertureless scanning near-field optical microscopy (aSNOM) to image dipolar and quadrupolar LSPPs of the bare sample with high fidelity in both amplitude and phase. This establishes a routine method for in situ optical microscopy of plasmonic and other resonant structures under ambient conditions.
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