Translation of Nanoantenna Hot-Spots by a Metal-Dielectric Composite Superlens

We employ numerical simulations to show that highly localized, enhanced electromagnetic fields, also known as "hot spots," produced by a periodic array of silver nanoantennas can be spatially translated to the other side of a metal-dielectric composite superlens. The proposed translation of the hot spots enables surface-enhanced optical spectroscopy without the undesirable contact of molecules with metal, and thus it broadens and reinforces the potential applications of sensing based on field-enhanced fluorescence and surface-enhanced Raman scattering.Comment: 9 pages, 4 figure

Micro-Directional Propagation Method Based on User Clustering

With the development of recommendation technology, it is of great significance to analyze users' digital footprints on social networking sites, extract user behavior rules, and make a relatively accurate assessment of each user's needs, to provide personalized services for users. It has been found that the users' behavior on social networking sites has a great correlation with the user's personalities. The OCEAN model's five characteristics can cover all aspects of user personality. There are some shortcomings in the current micro-directional propagation method. This paper has improved the traditional collaborative filtering method and proposed a collaborative filtering method based on user clustering. The model first clusters the users according to their OCEAN model, and then it filters the users collaboratively in the cluster to which the user belongs with the collaborative filtering method based on an optimized singular value decomposition (SVD) recommendation algorithm, called the BiasSVD recommendation algorithm -- to reduce the dimensionality of the data. Then it generates recommendations. Experiments show that clustering users' OCEAN models can improve the accuracy of recommendations. Compared with the entire user space, it greatly reduces the recommendation time, and effectively solves the cold start problem in micro directional propagation

A scalable and robust variance components method reveals insights into the architecture of gene-environment interactions underlying complex traits.

Understanding the contribution of gene-environment interactions (GxE) to complex trait variation can provide insights into disease mechanisms, explain sources of heritability, and improve genetic risk prediction. While large biobanks with genetic and deep phenotypic data hold promise for obtaining novel insights into GxE, our understanding of GxE architecture in complex traits remains limited. We introduce a method to estimate the proportion of trait variance explained by GxE (GxE heritability) and additive genetic effects (additive heritability) across the genome and within specific genomic annotations. We show that our method is accurate in simulations and computationally efficient for biobank-scale datasets. We applied our method to common array SNPs (MAF ≥1%), fifty quantitative traits, and four environmental variables (smoking, sex, age, and statin usage) in unrelated white British individuals in the UK Biobank. We found 68 trait-E pairs with significant genome-wide GxE heritability (p<0.05/200) with a ratio of GxE to additive heritability of ≈6.8% on average. Analyzing ≈8 million imputed SNPs (MAF ≥0.1%), we documented an approximate 28% increase in genome-wide GxE heritability compared to array SNPs. We partitioned GxE heritability across minor allele frequency (MAF) and local linkage disequilibrium (LD) values, revealing that, like additive allelic effects, GxE allelic effects tend to increase with decreasing MAF and LD. Analyzing GxE heritability near genes highly expressed in specific tissues, we find significant brain-specific enrichment for body mass index (BMI) and basal metabolic rate in the context of smoking and adipose-specific enrichment for waist-hip ratio (WHR) in the context of sex

Room-Temperature entangled quantum processor on integrated semiconductor photonics platform

The rise of the 4H-silicon-carbide-on-insulator (SiCOI) platform marks a promising pathway towards the realization of monolithic quantum photonic networks. However, the challenge of establishing room-temperature entangled registers on these integrated photonics platforms remains unresolved. Herein, we demonstrate the first entangled processor on the SiCOI platform. We show that both deterministic generation of single divacancy electron spins and near-unity spin initialization of a single $^{13}$C nuclear spin can be achieved on SiCOI at room temperature. Besides coherently manipulating the single nuclear spin, a maximally entangled state with a fidelity of 0.89 has been prepared on this CMOS-compatible semiconductor-integrated photonics system. This work establishes the foundation for compact and on-chip solutions within existing defect-based computing and sensing protocols, positioning the SiCOI platform as the most promising candidate for integrated monolithic quantum photonic networks.Comment: 16 pages, 4 figure

Studies of plasmonic hot-spot translation by a metal-dielectric layered superlens

We have studied the ability of a lamellar near-field superlens to transfer an enhanced electromagnetic field to the far side of the lens. In this work, we have experimentally and numerically investigated superlensing in the visible range. By using the resonant hot-spot field enhancements from optical nanoantennas as sources, we investigated the translation of these sources to the far side of a layered silver-silica superlens operating in the canalization regime. Using near-field scanning optical microscopy (NSOM), we have observed evidence of superlens-enabled enhanced-field translation at a wavelength of about 680 nm. Specifically, we discuss our recent experimental and simulation results on the translation of hot spots using a silver-silica layered superlens design. We compare the experimental results with our numerical simulations and discuss the perspectives and limitations of our approach

Control of LED Emission with Functional Dielectric Metasurfaces

The improvement of light-emitting diodes (LEDs) is one of the major goals of optoelectronics and photonics research. While emission rate enhancement is certainly one of the targets, in this regard, for LED integration to complex photonic devices, one would require to have, additionally, precise control of the wavefront of the emitted light. Metasurfaces are spatial arrangements of engineered scatters that may enable this light manipulation capability with unprecedented resolution. Most of these devices, however, are only able to function properly under irradiation of light with a large spatial coherence, typically normally incident lasers. LEDs, on the other hand, have angularly broad, Lambertian-like emission patterns characterized by a low spatial coherence, which makes the integration of metasurface devices on LED architectures extremely challenging. A novel concept for metasurface integration on LED is proposed, using a cavity to increase the LED spatial coherence through an angular collimation. Due to the resonant character of the cavity, extending the spatial coherence of the emitted light does not come at the price of any reduction in the total emitted power. The experimental demonstration of the proposed concept is implemented on a GaP LED architecture including a hybrid metallic-Bragg cavity. By integrating a silicon metasurface on top we demonstrate two different functionalities of these compact devices: directional LED emission at a desired angle and LED emission of a vortex beam with an orbital angular momentum. The presented concept is general, being applicable to other incoherent light sources and enabling metasurfaces designed for plane waves to work with incoherent light emitters.Comment: 29 pages, 6 figure

Inverse design for material anisotropy and its application for a compact X-cut TFLN on-chip wavelength demultiplexer

Inverse design focuses on identifying photonic structures to optimize the performance of photonic devices. Conventional scalar-based inverse design approaches are insufficient to design photonic devices of anisotropic materials such as lithium niobate (LN). To the best of our knowledge, this work proposes for the first time the inverse design method for anisotropic materials to optimize the structure of anisotropic-material based photonics devices. Specifically, the orientation dependent properties of anisotropic materials are included in the adjoint method, which provides a more precise prediction of light propagation within such materials. The proposed method is used to design ultra-compact wavelength division demultiplexers in the X-cut thin-film lithium niobate (TFLN) platform. By benchmarking the device performances of our method with those of classical scalar-based inverse design, we demonstrate that this method properly addresses the critical issue of material anisotropy in the X-cut TFLN platform. This proposed method fills the gap of inverse design of anisotropic materials based photonic devices, which finds prominent applications in TFLN platforms and other anisotropic-material based photonic integration platforms

Plasmonic nano-structures: Design, modeling, and characterization

Nanometer-scale plasmonic structures have a wide variety of applications in optics and photonics, with examples such as nano-lithography, biomedical sensing, photovoltaics, integrated photonic circuits, optical data storage, near-field scanning optical microscopy, and quantum information processing. Their optical characteristics, such as resonance wavelength, local field enhancements and effective permittivities and permeabilities, are of critical importance for performance optimization. In this report, three types of plasmonic devices have been studied: superlens, nanoantennas, and integrated superlens-nanoantenna devices. Numerical and analytical modeling methods have been developed to model and optimize these devices, and actual devices have been fabricated and experimentally characterized. Spatial harmonic analysis, also known as Fourier modal method or rigorous coupled-wave analysis, is a meshless method to solve Maxwell’s Equations rigorously for periodic structures. Computer codes of spatial harmonic analysis have been developed in this study and used for modeling nanoantenna arrays and metallic gratings. Excellent match between numerical and experimental results has been achieved for multiple incident angles and in a wide spectra range both above and below diffraction threshold. The two-dimensional spatial harmonic analysis modeling tool has been staged on-line at NanoHub and is freely available to the public. Superlens is a slab of metal sandwiched between two dielectric layers. Such a slab can form images of objects in close vicinity without suffering from the diffraction limit that is intrinsic in conventional imaging systems, therefore has great potentials in applications such as nano-lithography where sub-wavelength resolution is highly desired. The superlens based on the original idea works at very limited wavelengths determined by the permittivities of metal and the surrounding dielectrics. This study shows that by tuning the thicknesses of the metal and dielectric layers it is possible to make a superlens that works at an arbitrary predefined wavelength in a wide spectral range. Numerical analysis of single- and multi- layer superlens show that the designs of superlens depend on the objects therefore need to be optimized for specific cases. Nanoantennas are paired nano-particles with a small gap between them. Under resonance conditions nanoantennas can create strong local fields inside the gaps, also known as hot-spots, which are particularly useful in applications such as surface enhanced Raman scattering, surface enhanced fluorescence, and optical trapping. In this study transmittance and reflectance spectra of nanoantenna arrays are measured to study their resonance features. Then, finite element method and spatial harmonic analysis techniques are employed to model the electrodynamics of the nanoantennas. Both numerical techniques show good agreement with each other, as well as with the experimental results. These numerical methods are then used to investigate the near fields of nanoantennas and verify that nanoantennas can generate significantly enhanced fields inside their gaps. The relations between nanoantenna dimensions, resonance wavelengths, and field enhancements are systematically studied. A new device combining a superlens and a nanoantenna array is proposed, and it is demonstrated by numerical modeling in this study that this device can translate the hot-spots generated by the nanoantenna array to the other side of the superlens. The translation makes good use of the hot-spots while avoiding undesired effects, such as quenching, that happen when molecules are too close to metal surfaces. This device has great potentials in the areas of surface-enhanced Raman scattering, surface-enhanced fluorescence, and optical tweezers

Near field enhancement in silver nanoantenna-superlens systems

We demonstrate near field enhancement generation in silver nanoantenna-superlens systems via numerical modeling. Using near-field interference and global optimization algorithms, we can design nanoantenna-superlens systems with mismatched permittivities, whose performance can match those with matched permittivities. The systems studied here may find broad applications in the fields of sensing, such as field-enhanced fluorescence and surface-enhanced Raman scattering, and the methodology used here can be applied to the designing and optimization of other devices, such as two-dimensional near field focusing lens. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732793