157 research outputs found
Deep learning for topological photonics
No full textIn this paper, we review the specific field that combines topological photonics and deep learning (DL). Recent progress of topological photonics has attracted enormous interest for its novel and exotic properties such as unidirectional propagation of electromagnetic waves and robust manipulation of photons. These phenomena are expected to meet the growing demands of next-generation nanophotonic devices. However, to model and engineer such highly-complex systems are challenging. Recently, DL, a subset of machine learning methods using neural network (NN) algorithms, has been introduced in the field of nanophotonics as an effective way to capture a complex nonlinear relationship between design parameters and their corresponding optical properties. In particular, among various fields of nanophotonics, DL applications to topological photonics empowered by NN models have shown astonishing results in capturing the global material properties of topological systems. This review presents fundamental concepts of topological photonics and the basics of DL applied to nanophotonics in parallel. Recent studies of DL applications to topological systems using NN models are discussed thereafter. The summary and outlook showing the potential of taking data-driven approaches in topological photonics research and general physics are also discussed. [GRAPHICS] .11Nsciescopu
Deep sub-wavelength nanofocusing of UV-visible light by hyperbolic metamaterials
No full textConfining light into a sub-wavelength area has been challenging due to the natural phenomenon of diffraction. In this paper, we report deep sub-wavelength focusing via dispersion engineering based on hyperbolic metamaterials. Hyperbolic metamaterials, which can be realized by alternating layers of metal and dielectric, are materials showing opposite signs of effective permittivity along the radial and the tangential direction. They can be designed to exhibit a nearly-flat open isofrequency curve originated from the large-negative permittivity in the radial direction and small-positive one in the tangential direction. Thanks to the ultraflat dispersion relation and curved geometry of the multilayer stack, hyperlens can magnify or demagnify an incident beam without diffraction depending on the incident direction. We numerically show that hyperlens-based nanofocusing device can compress a Gaussian beam down to tens-of-nanometers of spot size in the ultraviolet (UV) and visible frequency range. We also report four types of hyperlenses using different material combinations to span the entire range of visible frequencies. The nanofocusing device based on the hyperlens, unlike conventional lithography, works under ordinary light source without complex optics system, giving rise to practical applications including truly nanoscale lithography and deep sub-wavelength scale confinement.1165Nsciescopu
Deep sub-wavelength nanofocusing of ultraviolet and visible light by hyperbolic metamaterials
No full text1
A static bug detector for uninitialized field references in Java programs
No full textCorrectness of Java programs is important because they are executed in distributed computing environments. The object initialization scheme in the Java programming language is complicated, and this complexity may lead to undesirable semantic bugs. Various tools have been developed for detecting program patterns that might cause errors during program execution. However, current tools cannot identify code patterns in which an uninitialized field is accessed when an object is initialized. We refer to such erroneous patterns as uninitialized field references. In this paper, we propose a static pattern detection algorithm for identifying uninitialized field references. We design a sound analysis for this problem and implement an analyzer using the Soot framework. In addition, we apply our algorithm to some real Java applications. From the experiments, we identify 12 suspicious field references in the applications, and among those we find two suspected errors by manual inspection.This research was supported by the MIC (Ministry of Information and Communication), Korea, under the ITRC (Information Technology Research Center) support program supervised by the IITA. (Institute of Information Technology Assessment) (IITA-2005-C1090-0502-0031
Sternaspis sunae Wu & Xu, 2017, sp. nov.
No full textSternaspis sunae sp. nov. Figure 8 Type material. South China Sea. Holotype: MBM 198787, R/V sy3, Nansha Islands, Sta. 59, 224 m, 22 Sep. 1994. Paratype: MBM238398 (1 spec.), same collection information as the holotype. Body partly shrinks, 30 mm long, 10.9 mm wide; abdomen 16.2 mm long; left shield plate 4.84 mm long, 5.65 mm wide. Description. Holotype (MBM 198787) complete, 38 mm long, 17 mm wide; abdomen 25 mm long; left shield plate 5.23 mm long, 6.21 mm wide. Body pale to yellowish, introvert fully exposed, with similar pigmentation as abdomen, constriction or waist segments relaxed (Fig. 8 A). Prostomium hemispherical, translucent pale (Fig. 8 B). Eyespots not seen. Boundary distinct on side and back of prostomium. Peristomium projected, covered with sediment particles, barely extending laterally and ventrally to anterior margin of first chaetiger. Mouth circular, projected, wider than prostomium, covered by minute papillae (Fig. 8 B). First three chaetigers each with 14–17 light brown hooks per side. Hooks slightly expanded sub-distally, spearhead-like with a medial furrow; hooks gradually shortened towards ventrolateral side (Fig. 8 B–D). Introvert covered by minute papillae. Genital papillae conical, with indistinct annular rings, protruding ventro-laterally from inter-segmental groove between segments 7 and 8. Anterior abdomen with 7 segments, partly covered by sediment; papillae minute, evenly distributed (Fig. 8 A, E). Capillaries not seen. Ventro-caudal shield brick red, with distinct concentric lines near margin; shield nearly rectangular, much wider than long (width-length ratio: 2.33–2.37) (Fig. 8 G, H). Anterior margins angular, anterior depression shallow; anterior keels covered by translucent integument layer. Suture restricted to anterior region, fused posteriorly into a furrow. Lateral margins straight, smooth, expanded posteriorly. Main ribs distinct, forming a shallow groove between lateral plates and fan; fan slightly ribbed, truncate, not extending beyond posterolateral corners; margin smooth or slightly crenulated, without a distinct median notch (Fig. 8 G, H). Marginal chaetae golden yellow, including 10 lateral fascicles and 6 posterior ones (Fig. 8 G, H); lateral fascicles successively longer from anterior to posterior, chaetae arranged in semi-closed oval; posterior fascicles similar in length, chaetae in linear arrangement. Peg chaetae tapering, with stout base. A small fascicle of very long, delicate capillary chaetae located in upper edge of peg chaetae. A fascicle of shorter capillary chaetae inserted between peg chaetae and outermost posterior fascicle, at least 3 times as long as posterior chaetae. Branchiae abundant, inserted on two plates. Branchial filaments slender, spiraled or curled; inter-branchial papillae long, curled, covered with fine sediment particles. Branchial plates oval, nearly parallel, with unclear boundaries (Fig. 8 F). Variations. The lateral margins of the shield are nearly straight (Fig. 8 G) or slightly expanded posteriorly (Fig. 8 H). The branchial plates are almost parallel in the holotype (Fig. 8 F) but divergent in the paratype. Etymology. Sternaspis sunae is named to honor Professor Ruiping Sun, in recognition of her contribution to the polychaete taxonomy in China, and in appreciation of her mentoring to the first author during the graduate student period. Distribution. South China Sea off the Nansha Islands (water depth 224 m). Remarks. The introvert hooks of Sternaspis sunae sp. nov. are spearhead-like with a median longitudinal furrow in the end portion, resembling those present in the genus Petersenaspis (Figs 2 F; 8D). However, all species of Petersenaspis have 8 segments in the pre-shield abdomen, and their shields have feebly developed ribs and no concentric lines. By contrast, S. sunae sp. nov. has seven segments in the pre-shield region and both radial ribs and concentric lines are well developed in the shield, like members of Sternaspis. These distinct features indicate the new species should be classified into the genus Sternaspis, though most species of Sternaspis have tapering introvert hooks. Sternaspis sunae sp. nov. is most similar to the new species S. wui sp. nov. described above because they have nearly rectangular ventro-caudal shields, six posterior chaetal fascicles, and similar color and arrangement of the chaetal fascicles. The two species differ clearly in the shape of the introvert hooks, which are spearhead-like with a median longitudinal furrow in S. sunae sp. nov., but are tapering in S. wui sp. nov. (Figs 7 D; 8D). Besides, the two species can also be distinguished by the features of the shield. Sternaspis sunae sp. nov. has the shield suture restricted only in the anterior region and the concentric lines only visible near the margin, while in S. wui sp. nov. the suture extends throughout the shield and the concentric lines are distinct from the margin to the center.Published as part of Wu, Xuwen & Xu, Kuidong, 2017, Diversity of Sternaspidae (Annelida: Terebellida) in the South China Sea, with descriptions of four new species, pp. 403-415 in Zootaxa 4244 (3) on page 413, DOI: 10.11646/zootaxa.4244.3.8, http://zenodo.org/record/43060
Thermally robust ring-shaped chromium perfect absorber of visible light
No full textA number of light-absorbing devices based on plasmonic materials have been reported, and their device efficiencies (or absorption) are high enough to be used in real-life applications. Many light-absorbing applications such as thermophotovoltaics and energy-harvesting and energy-sensing devices usually require high-temperature durability; unfortunately, noble metals used for plasmonics are vulnerable to heat. As an alternative, refractory plasmonics has been introduced using refractory metals such as tungsten (3422 degrees C) and transition metal nitrides such as titanium nitride (2930 degrees C). However, some of these materials are not easy to handle for device fabrications owing to their ultra-high melting point. Here, we propose a light absorber based on chromium (Cr), which is heat tolerant due to its high melting temperature (1907 degrees C) and is compatible with fabrication using conventional semiconductor manufacturing processes. The fabricated device has >95% average absorption of visible light (500-800 nm) independent of polarization states. To verify its tolerance of heat, the absorber was also characterized after annealing at 600 degrees C. Because of its compactness, broadband operational wavelength, and heat tolerance, this Cr perfect absorber will have applications in high-temperature photonic devices such as solar thermophotovoltaics.111Ysciescopu
Fabrication of three-dimensional suspended, interlayered and hierarchical nanostructures by accuracy-improved electron beam lithography overlay
No full textNanofabrication techniques are essential for exploring nanoscience and many closely related research fields such as materials, electronics, optics and photonics. Recently, three-dimensional (3D) nanofabrication techniques have been actively investigated through many different ways, however, it is still challenging to make elaborate and complex 3D nanostructures that many researchers want to realize for further interesting physics studies and device applications. Electron beam lithography, one of the two-dimensional (2D) nanofabrication techniques, is also feasible to realize elaborate 3D nanostructures by stacking each 2D nanostructures. However, alignment errors among the individual 2D nanostructures have been difficult to control due to some practical issues. In this work, we introduce a straightforward approach to drastically increase the overlay accuracy of sub-20 nm based on carefully designed alignmarks and calibrators. Three different types of 3D nanostructures whose designs are motivated from metamaterials and plasmonic structures have been demonstrated to verify the feasibility of the method, and the desired result has been achieved. We believe our work can provide a useful approach for building more advanced and complex 3D nanostructures.114sciescopu
- …
