Generation of 11-fs dark pulses via coherent perfect absorption in plasmonic metamaterial

Dark pulses are dips in power of electro magnetic radiation on a constant background that are often accompanied by a phase jump across the intensity minimum. Since their discovery, dark pulses have attracted considerable attention in many fields such as dark solitons and optical communications. Here we report generation of 11 fs dark pulses using the regime of “perfect absorption”. When two coherent counter-propagating electromagnetic waves of the same intensity form a standing wave, a thin absorber placed in the antinode of the wave could completely dissipate energy of both waves if its traveling wave absorption is 50%. If one of the waves is a “gate pulse” in time domain, the “perfect absorption” regime will exist only during the pulse, when a dip in power of “carrier pulse” will be created. “Dark pulses” are generated by positioning plasmonic absorber in the anti-node of the standing wave and balancing peak intensities . These dark pulses are characterized using cross-correlation technique. Measured width of the “dark pulse” is border than 6 fs “gate pulse”, which is nearly 11fs as shown in Fig. 1B. Width of the “dark pulse” is limited by transient plasmonic absorption establishes with completion of the plasmon relaxation time, which is typically 11fs in gold nanostructures. We argue that bandwidth of dark pulses is limited by the plasmon relaxation time of the absorber

A new advanced query response time and reduce CPU cost in web search

I proposed the Predictive Energy Saving Online Scheduling (PESOS) calculation. With regards to web crawlers, PESOS intends to decrease the CPU energy utilization of an inquiry preparing hub while forcing required tail dormancy on the question reaction times. For each inquiry, PESOS chooses the most minimal conceivable CPU center recurrence with the end goal that the energy utilization is diminished and the due dates are regarded. PESOS choose the correct CPU center recurrence misusing two various types of query efficiency predictors (QEPs). The first QEP gauges the preparing volume of inquiries. The second QEP gauges the inquiry preparing times under various center frequencies, given the quantity of postings to score. Since QEPs can be off base, amid their preparation we recorded the root mean square error (RMSE) of the expectations

Metamaterial enhancement of metal-halide perovskite luminescence

Metal-halide perovskites are rapidly emerging as solution-processable optical materials for light-emitting applications. Here, we adopt a plasmonic metamaterial approach to enhance photoluminescence emission and extraction of methylammonium lead iodide (MAPbI3) thin films based on the Purcell effect. We show that hybridization of the active metal-halide film with resonant nanoscale sized slits carved into a gold film can yield more than 1 order of magnitude enhancement of luminescence intensity and nearly 3-fold reduction of luminescence lifetime corresponding to a Purcell enhancement factor of more than 300. These results show the effectiveness of resonant nanostructures in controlling metal-halide perovskite light emission properties over a tunable spectral range, a viable approach toward highly efficient perovskite light-emitting devices and single-photon emitter

Topological insulator BSTS as a broadband switchable metamaterial

The development of metamaterials into a viable platform for nanophotonic applications, data processing circuits, sensors, etc. requires identification of new plasmonic materials to overcome the limitations of noble metals, in particular their high losses. Here we describe a class of topological insulator materials which support broadband plasmonic response and possess extremely appealing photonic properties ranging from mid-IR to UV. Bi1.5Sb0.5Te1.8Se1.2 (BSTS) is a bulk insulator with robust conducting surface states protected by time-reversal symmetry, due to the strong spin-orbit coupling. BSTS single crystals were synthesized by melting high-purity Bi, Sb, Te and Se powders at 950°C in an evacuated quartz tube. The temperature was then gradually decreased to room temperature over a span of three weeks. The resulting crystals were then cleaved along the (100) family of planes to a thickness of ~0.5 mm. BSTS dielectric constants were derived by ellipsometric measurements and appear to be in excellent agreement with first principle DFT calculations. Unlike common direct or indirect bandgap semiconductors, the anomalous dispersion region falls in the visible part of the spectrum, leading to negative values of the permittivity. This behavior of the optical response is attributed to a combination of bulk interband transitions and surface contribution of the topologically protected states. To prove metallic behavior of BSTS, we fabricated metamaterials and gratings on crystal flakes and registered strong plasmonic response from UV to NIR. The coexistence of plasmonic response of the topological surface with dielectric properties of the semiconducting bulk enables ultrafast (t>100 fs) and broadband (to mid-IR) photo-modulation of the optical response. These findings show the potential of topological insulators as a platform for high-frequency switchable plasmonic metamaterials

Analysis of fracture processes in cortical bone tissue

This article has been published in the journal, Engineering Fracture Mechanics [© Elsevier Ltd]. The definitive version is available at: http://dx.doi.org/10.1016/j.engfracmech.2012.11.020Bones are the principal structural components of a skeleton; they play unique roles in the body providing its shape maintenance, protection of internal organs and transmission of forces. Ultimately, their structural integrity is vital for the quality of life. Unfortunately, bones can only sustain loads until a certain limit, beyond which they fail. Understanding a fracture behaviour of bone is necessary for prevention and diagnosis of trauma; this can be achieved by studying mechanical properties of bone, such as its fracture toughness. Generally, most of bone fractures occur in long bones consisting mostly of cortical bone tissue. Therefore, in this paper, an experimental study and numerical simulations of fracture processes in a bovine femoral cortical bone tissue were considered. A set of experiments was conducted to characterise fracture toughness of the bone tissue in order to gain basic understanding of spatial variability and anisotropy of its resistance to fracture and its link to an underlying microstructure. The data was obtained using single-edge-notch-bending specimens of cortical bone tested in a three-point bending setup; fracture surfaces of specimens were studied using scanning electron microscopy. Based on the results of those experiments, a number of finite-element models were developed in order to analyse its deformation and fracture using the extended finite-element method (X-FEM). Experimental results of this study demonstrate both variability and anisotropy of fracture toughness of the cortical bone tissue; the developed models adequately reflected the experimental data

Unraveling the ultralow threshold stimulated emission from CdZnS/ZnS quantum dot and enabling high-Q microlasers

The newly engineered ternary CdZnS/ZnS colloidal quantum dots (CQDs) are found to exhibit remarkably high photoluminescence quantum yield and excellent optical gain properties. However, the underlying mechanisms, which could offer the guidelines for devising CQDs for optimized photonic devices, remain undisclosed. In this work, through comprehensive steady-state and time-resolved spectroscopy studies on a series of CdZnS-based CQDs, we unambiguously clarify that CdZnS-based CQDs are inherently superior optical gain media in the blue spectral range due to the slow Auger process and that the ultralow threshold stimulated emission is enabled by surface/interface engineering. Furthermore, external cavity-free high-Q quasitoroid microlasers were produced from self-assembly of CdZnS/ZnS CQDs by facile inkjet printing technique. Detailed spectroscopy analysis confirms the whispering gallery mode lasing mechanism of the quasitoroid microlasers. This tempting microlaser fabrication method should be applicable to other solution-processed gain materials, which could trigger broad research interests. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA

On the in vitro fatigue behavior of human dentin with implications for life prediction

Although human dentin is known to be susceptible to failure under repetitive cyclic fatigue loading, there are few reports in the literature that reliably quantify this phenomenon

Fracture process in cortical bone: X-FEM analysis of microstructured models

This article was published in the serial International Journal of Fracture [© Springer Science and Business Media]. The definitive version is available at: http://dx.doi.org/10.1007/s10704-013-9814-7Bones tissues are heterogeneous materials that consist of various microstructural features at different length scales. The fracture process in cortical bone is affected significantly by the microstructural constituents and their heterogeneous distribution. Understanding mechanics of bone fracture is necessary for reduction and prevention of risks related to bone fracture. The aim of this study is to develop a finite-element approach to evaluate the fracture process in cortical bone at micro-scale. In this study, three microstructural models with various random distributions based on statistical realizations were constructed using the global model's framework together with a submodelling technique to investigate the effect of microstructural features on macroscopic fracture toughness and microscopic crack-propagation behaviour. Analysis of processes of crack initiation and propagation utilized the extended finite-element method using energy-based cohesive-segment scheme. The obtained results were compared with our experimental data and observations and demonstrated good agreement. Additionally, the microstructured cortical bone models adequately captured various damage and toughening mechanisms observed in experiments. The studies of crack length and fracture propagation elucidated the effect of microstructural constituents and their mechanical properties on the microscopic fracture propagation process. © 2013 Springer Science+Business Media Dordrecht

Deep Eyedentification: Biometric Identification using Micro-Movements of the Eye

We study involuntary micro-movements of the eye for biometric identification. While prior studies extract lower-frequency macro-movements from the output of video-based eye-tracking systems and engineer explicit features of these macro-movements, we develop a deep convolutional architecture that processes the raw eye-tracking signal. Compared to prior work, the network attains a lower error rate by one order of magnitude and is faster by two orders of magnitude: it identifies users accurately within seconds