Waveguide effective plasmonics with structure dispersion

Plasmonic phenomena on the surface between metal and dielectric have received extensive attention, and have boosted a series of exciting techniques. Plasmonics describes the interaction between light and electronics and shows great potential in nanophotonics, optoelectronic devices, quantum physics, and surface-enhanced spectroscopy, etc. However, plasmonic phenomena are always suffering from the inherent loss issue of plasmonic materials at optical frequency, which has restricted further applications of plasmonics. In this review, we focus on the technique of waveguide effective plasmonics, which is a feasible low-loss realization of plasmonic metamaterials in lower frequency based on the structural dispersion. This review provides the underlying physics of the waveguide effective plasmonics and its applications varying from classical plasmonic concepts to novel effective plasmonic devices. Finally, we make a brief discussion on the direction of future researches and a prospect of the potential applications.

A mathematical representation of protein binding sites using structural dispersion of atoms from principal axes for classification of binding ligands

Many researchers have studied the relationship between the biological functions of proteins and the structures of both their overall backbones of amino acids and their binding sites. A large amount of the work has focused on summarizing structural features of binding sites as scalar quantities, which can result in a great deal of information loss since the structures are three-dimensional. Additionally, a common way of comparing binding sites is via aligning their atoms, which is a computationally intensive procedure that substantially limits the types of analysis and modeling that can be done. In this work, we develop a novel encoding of binding sites as covariance matrices of the distances of atoms to the principal axes of the structures. This representation is invariant to the chosen coordinate system for the atoms in the binding sites, which removes the need to align the sites to a common coordinate system, is computationally efficient, and permits the development of probability models. These can then be used to both better understand groups of binding sites that bind to the same ligand and perform classification for these ligand groups. We demonstrate the utility of our method for discrimination of binding ligand through classification studies with two benchmark datasets using nearest mean and polytomous logistic regression classifiers.

Classification of protein binding ligands using structural dispersion of binding site atoms from principal axes

Many researchers have studied the relationship between the biological functions of proteins and the structures of both their overall backbones of amino acids and their binding sites. A large amount of the work has focused on summarizing structural features of binding sites as scalar quantities, which can result in a great deal of information loss since the structures are three-dimensional. Additionally, a common way of comparing binding sites is via aligning their atoms, which is a computationally intensive procedure that substantially limits the types of analysis and modeling that can be done. In this work, we develop a novel encoding of binding sites as covariance matrices of the distances of atoms to the principal axes of the structures. This representation is invariant to the chosen coordinate system for the atoms in the binding sites, which removes the need to align the sites to a common coordinate system, is computationally efficient, and permits the development of probability models. These can then be used to both better understand groups of binding sites that bind to the same ligand and perform classification for these ligand groups. We demonstrate the effectiveness of our method through classification studies with two benchmark datasets using nearest mean and polytomous logistic regression classifiers.

Broadband dispersive free, large, and ultrafast nonlinear material platforms for photonics

Broadband dispersion free, large and ultrafast nonlinear material platforms comprise the essential foundation for the study of nonlinear optics, integrated optics, intense field optical physics, and quantum optics. Despite substantial research efforts, such material platforms have not been established up to now because of intrinsic contradictions between large nonlinear optical coefficient, broad operating bandwidth, and ultrafast response time. In this work, a broadband dispersion free, large and ultrafast nonlinear material platform based on broadband epsilon-near-zero (ENZ) material is experimentally demonstrated, which is designed through a novel physical mechanism of combining structural dispersion and material dispersion. The broadband ENZ material is constructed of periodically nanostructured indium tin oxide (ITO) films, and the structure is designed with the help of theoretical predictions combined with algorithm optimization. Within the whole broad ENZ wavelength range (from 1300 to 1500 nm), a wavelength-independent and large average nonlinear refractive index of −4.85 × 10−11 cm2/W, which is enlarged by around 20 times than that of an unstructured ITO film at its single ENZ wavelength, and an ultrafast response speed at the scale of Tbit/s are experimentally reached simultaneously. This work not only provides a new approach for constructing nonlinear optical materials but also lays the material foundation for the application of nanophotonics.

Structural dispersion–based reduction of loss in epsilon-near-zero and surface plasmon polariton waves

The field of plasmonics has substantially affected the study of light-matter interactions at the subwavelength scale. However, dissipation losses still remain an inevitable obstacle in the development of plasmonic-based wave propagation. Although different materials with moderate losses are being extensively studied, absorption arguably continues to be the key challenge in the field. Here, we theoretically and numerically investigate a different route toward the reduction of loss in propagating plasmon waves. Rather than focusing on a material-based approach, we take advantage of structural dispersion in waveguides to manipulate effective material parameters, thus leading to smaller losses. The potential of this approach is illustrated with two examples: plane-wave propagation within a bulk epsilon-near-zero medium and surface plasmon polariton propagation at the interface of a medium with negative permittivity. We provide the recipe for a practical implementation at mid-infrared frequencies. Our results might represent an important step toward the development of low-loss plasmonic technologies.