摘要：
Collaborative enhancements from surface plasmons (SPs) and whispering-gallery modes (WGMs) can induce intense near-field effects with high spatial localization around the surface of a semiconducting material. One can construct a highly efficient hybrid microcavity using semiconducting materials through resonant coupling between SPs and WGMs. Hexagonal ZnO micro-/nanostructures, which have been employed as natural WGM microcavities for ultraviolet (UV) lasing, can be used as ideal platforms to construct such hybrid microcavities. Here, we comprehensively review the recent efforts for improving lasing performance by resonant coupling between SPs and WGMs. Traditional SPs originating from various metals as well as novel SPs originating from atomic layers such as graphene are considered. Moreover, we discuss the mechanism of light-matter interactions beyond the improvements in lasing performance.
摘要：
We experimentally study the spatiotemporal evolution of chirped femtosecond laser pulses at a specific spatial position, such as the modulation peak position (MPP), during small-scale self-focusing (SSSF). It is found that the spatial peak intensity at the MPP increases rapidly initially with increment of input power due to the effect of SSSF, however it becomes saturated at the higher power because the finite energy of the beam restraints increasing of the peak intensity at the MPP. The pulse width at the MPP is compressed gradually with rising power owing to the spatiotemporal coupling effect, which will reach the narrowest when the spatial peak intensity at the MPP reaches the maximum. Further, the influence of chirp on the pulse width evolution at the MPP is discussed theoretically. We find that the negative chirp accelerates the pulse width compression because the negative chirp enhances the process of SSSF, but the positive chirp is counterproductive. Our results may provide some helps for propagation and amplification of broadband laser pulses.
摘要：
When a low-power finite-energy Airy pulse (FEAP) and a high-power soliton pulse simultaneously propagate in an optical fiber, we numerically study the evolution of the FEAP affected by higher-order effects, including third-order dispersion (TOD), Raman scattering and self-steepening (SS). It is found that shedding solitons are generated from the FEAP due to the effect of cross-phase modulation (XPM). The TOD only affects the center position of the shedding soliton, but does not change the spectrum structure. The truncation coefficient of a FEAP, TOD and SS can be used to manipulate the Raman-induced frequency shift (RIFS). It is demonstrated that the RIFS is suppressed obviously by both positive TOD, SS and a small truncation coefficient, but the RIFS is enhanced by the negative TOD and a larger truncation coefficient. Further, we comparatively study the simultaneous contributions of TOD, Raman, and SS to the evolution of a FEAP and a Sech pulse, respectively. It is shown that the FEAP generates some static solitons besides the conventional Raman soliton and the whole spectrum is broadened that extended towards to the blue-shifted side besides the conventional red-shifted components. Our results indicate that the FEAP has potential application in supercontinuum generation and broadband sources.
摘要：
For large-scale sparse matrices, SpMV cannot be processed on GPU using the common storage formats because of the memory limitation. In addition, the parallel effect is poor using general formats for the sparse matrices with extremely uneven distribution of non-zero elements, which leads to performance deterioration. This paper presents an optimal partitioning strategy based on the distribution of non-zero elements in a sparse matrix to improve the performance of SpMV, and uses a hybrid format, which mixes CSR and ELL formats, to store the blocks partitioned from the sparse matrix. The hybrid blocked format has better compression effect and more uniform distribution of non-zero elements, which can be suitable for more types of sparse matrices. Our partitioning strategy is proven to be optimal, which can yield the minimum parallel execution time on GPU. We develop an optimal partitioning strategy to improve the performance of SpMV.We present a reordering algorithm in which the time complexity is only O(Nlog2k).We employ a hybrid format to store a blocked sparse matrix partitioned by our optimal partitioning strategy. For large-scale sparse matrices, SpMV cannot be processed on GPU using the common storage formats because of the memory limitation. In addition, the parallel effect is poor using general formats for the sparse matrices with extremely uneven distribution of non-zero elements, which leads to performance deterioration. This paper presents an optimal partitioning strategy based on the distribution of non-zero elements in a sparse matrix to improve the performance of SpMV, and uses a hybrid format, which mixes CSR and ELL formats, to store the blocks partitioned from the sparse matrix. The hybrid blocked format has better compression effect and more uniform distribution of non-zero elements, which can be suitable for more types of sparse matrices. Our partitioning strategy is proven to be optimal, which can yield the minimum parallel execution time on GPU. We develop an optimal partitioning strategy to improve the performance of SpMV.We present a reordering algorithm in which the time complexity is only O(Nlog2k).We employ a hybrid format to store a blocked sparse matrix partitioned by our optimal partitioning strategy.
关键词：
Airy pulses;Pulse propagation and temporal solitons;Nonlinear optics
摘要：
We analytically and numerically investigate the propagation dynamics of initially chirped symmetric Airy pulses in an optical fiber. The results show that the positive chirps act to promote the interference in generating a focal point on the propagation axis, while the negative chirps tend to suppress the focusing effect, as compared to conventional unchirped symmetric Airy pulses. The numerical results demonstrate that the linear propagation of chirped symmetric Airy pulses depend considerably on the chirp parameter and the primary lobe position. In the anomalous dispersion region, positively chirped symmetric Airy pulses first undergo an initial compression, and reach a foci due to the opposite acceleration, and then experience a lossy inversion transformation, and come to the opposite facing focal position. The impact of truncation coefficient and Kerr nonlinearity on the chirped symmetric Airy pulses propagation is also disclosed separately.
摘要：
When laser pulses propagate in an inhomogeneous nonlinear medium, we theoretically investigate the evolution of laser pulses by analytically solving the (3 + 1)-dimensional generalized nonlinear Schrodinger equation with variable coefficients and optical lattice. A series of chirped-free and chirped analytic solutions, such as soliton solutions are found and intensities evolution of these analytic solutions are studied in detail. In the absence of optical lattice, we find that the intensities evolution of chirped-free and chirped analytic solutions vary regularly when the diffraction coefficient is the same as the dispersion coefficient. When the diffraction coefficient is different from the dispersion coefficient, the intensities evolution of chirped-free analytic solutions are regular variation, but the intensities evolution of chirped analytic solutions are irregular. In the presence of optical lattice, the intensities evolution of chirped analytic solutions vary regularly because the diffraction coefficient and the dispersion coefficient are always identical. (C) 2017 Elsevier GmbH. All rights reserved.
摘要：
[Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3]20 superlattices were epitaxially fabricated on (001) MgO substrates with 24 nm La0.5Ca0.5MnO3 (LCMO) buffer layer by pulsed laser deposition. As the thickness of Pr0.7Sr0.3MnO3 (PSMO) layer and LCMO layer is not identical, non-uniformity in the superlattice period thickness will occur and result in lower metal–insulator transition temperature and larger magnetoresistance (MR) at a wide low-temperature range. Furthermore, the percolation model was used to quantitatively understand the transport mechanism of superlattice. Our research results demonstrate that inhomogeneous layer thickness accompanied with charge ordering phase separation can strongly influence the transport properties of superlattice. Enhanced magnetoresistance at a wide temperature range provides possibilities for practical application in manganite-based film devices.
摘要：
For improving the quality of positron emission tomography (PET) images, the partial differential equation median (PDEmedian) algorithm which incorporates an anisotropic diffusion (AD) filter into the median root prior (MRP) algorithm was proposed. However, due to the shortcomings of the AD filter, the PDEmedian algorithm is difficult to realize. This work aims to solve this problem by introducing a new diffusion model into the PDEmedian. The proposed algorithm shows its positive effects on image reconstruction and denoising. Experimental results present that the new algorithm can preserve sharp edges while reducing noise at the same time. Furthermore, in comparison to other similar reconstruction algorithms, the proposed method is less sensitive to the value of the gradient threshold and the adjustment of the diffusion number.
作者机构：
[汪彦] School of Software, Central South University, Changsha, 410083, China;[涂立; 汪彦] School of Information and Electronic Engineering, Hunan City University, Yiyang, 413000, China
通讯机构：
School of Software, Central South University, Changsha, China
摘要：
In recent years, trap-related interfacial transport phenomena have received great attention owing to their potential applications in resistive switching devices and photo detectors. Not long ago, one new type of memristive interface that is composed of F-doped SnO_2 and Bi_2S_3 nano-network layers has demonstrated a bivariate-continuous-tunable resistance with a swift response comparable to the one in neuron synapses and with a brain-like memorizing capability. However, the resistive mechanism is still not clearly understood because of lack of evidence, and the limited improvement in the development of the interfacial device. By combining I-V characterization, electron energy-loss spectroscopy, and firstprinciple calculation, we studied in detail the macro/micro features of the memristive interface using experimental and theoretical methods, and confirmed that its atomic origin is attributed to the traps induced by O-doping. This implies that impurity-doping might be an effective strategy for improving switching features and building new interfacial memristors.
摘要：
Collective oscillations of free electrons generate plasmons on the surface of a material. A whispering-gallery microcavity effectively confines the light field on its surface based on the total reflection from its internal wall. When these two kinds of electromagnetic waves meet each other, the stimulated emissions from an individual ZnO microrod were enhanced more than 50-fold and the threshold was reduced after the whispering-gallery microcavity was coated with a monolayer of graphene and Al nanoparticles. The improvement of the lasing performance was attributed to the synergistic energy coupling of the graphene/Al surface plasmons with ZnO excitons. The lasing characteristics and the coupling mechanism were investigated systematically.
