Search

Leaky waves are complex eigenmodes compatible with radiation in terms of their momentum, which can be supported by open waveguiding structures and can be effective at modeling radiative phenomena from such systems. Here, a "flatland" analog of leaky‐wave radiation is introduced to describe a novel mechanism for in‐plane radiation leakage that can occur in artificial or natural low‐dimensional materials. Possible platforms are illustrated for its physical realization, in the form of suitably designed planar junctions of isotropic impedance surfaces that implement surface‐wave or line‐wave guiding structures. A simple and insightful semi‐analytical model for the radiation mechanism is developed and validated against full‐wave numerical simulations. These results provide a new tool for the advanced manipulation of surface waves at the nanoscale, which relies entirely on interface‐optics effects, and can find interesting applications in the emerging field of polaritonics. [ABSTRACT FROM AUTHOR]

Electromagnetic fields interacting with microscopic structural features in a composite material provide emerging optical properties that surpass those offered by the individual components. However, composite materials can be generally lossy due to the scattering effects induced by inhomogeneities at the interfaces between different compounds. To overcome such problems, complicated and costly manufacturing procedures, such as top‐down approaches, are generally required. In contrast, here ZnO–ZnWO4 eutectic self‐organized composites grown by the micropulling method are considered, displaying sharp and strongly polarized transmission at 397 nm. Such an optical response is notable because it is not observed in either ZnO or ZnWO4 single crystals. The optical response is due to the refractive index matching of the two constituents, which self‐organize into ordered structures via a micropulling down method. The optical behavior reported here can directly lead to applications, such as tunable narrowband filters with bandpass of 3 nm and polarizers, paving the way to a new self‐organization route for manufacturing optical components. [ABSTRACT FROM AUTHOR]

Phonon polaritons provide useful opportunities, complementary to those provided by plasmon polaritons, in the study of the interaction of light with matter at small scales. The focus of this review is on phonon polaritons in low‐dimensional van der Waals (vdW) materials and heterostructures. Phonon polaritons confined in vdW materials exhibit large electromagnetic localization and are easy to hybridize with other collective modes. The extreme optical anisotropy in vdW systems produces the natural hyperbolic dispersion, enabling the access to deep subdiffractional optics and often yielding improved figures of merit over hyperbolic metamaterials. These virtues hold promises for practical nanophotonic applications, including optical sensing, super‐resolution imaging, energy and emission engineering, quantum optics, and a next generation of optical circuit elements. [ABSTRACT FROM AUTHOR]

Metamaterial perfect absorbers (MPAs) are artificial materials composed of an array of subwavelength structures that manipulate electromagnetic waves to achieve extraordinary light absorption properties. Driven by the advent of the Internet of Things, MPAs are employed in microelectromechanical systems for the development of efficient and miniaturized IR detectors, imagers, and spectrometers, thanks to their lithographically tunable peak absorption, spectral selectivity, and ultrathin thickness. MPAs characterized by high absorptance in narrow spectral bands are particularly desirable for the implementation of high‐resolution IR spectroscopic sensors. Yet, no accurate analytical model is currently available to guide the design of an MPA with ultra‐narrow absorption bandwidth, while meeting all the stringent requirements for spectroscopic sensors. Here, a circuit model capable of accurately predicting spectral responses of metal–insulator–metal (MIM) IR absorbers is reported. The model is experimentally validated in the mid‐wavelength IR spectral range and exploited for the first demonstration of an MIM IR absorber that exhibits performance approaching the predicted physical limits: full‐width at half‐maximum ≈3% and near‐unity absorption (η > 99.7%) at 5.83 µm wavelength, while independent of incident angle and polarization of the impinging IR radiation. These unprecedented absorption properties are key enablers for the development of miniaturized, low‐cost, and high‐resolution spectrometers. Ultra‐narrowband metamaterial infrared absorbers and the modified lumped circuit model are presented. The accurate spectral responses obtained by the circuit model are utilized to optimize the design of metal–insulator–metal (MIM) infrared absorbers for high spectral selectivity. The model is experimentally validated and exploited for the first demonstration of a MIM infrared absorber that exhibits performance approaching the predicted physical limits. [ABSTRACT FROM AUTHOR]