Shanghai Key Laboratory of Modern Optical Systems

Shanghai, China

Shanghai Key Laboratory of Modern Optical Systems

Shanghai, China
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Qin C.,Shanghai Key Laboratory of Modern Optical Systems | Zhang X.,Shanghai University
Journal of Visual Communication and Image Representation | Year: 2015

In this paper, we propose a novel reversible data hiding scheme in encrypted image. The content owner encrypts the original image with the encryption key to achieve privacy protection for image content, and then, each block of the encrypted image is embedded with one secret bit by the data hider using the data-hiding key. Through the elaborate selection for partial pixels to be flipped, data hiding process only conducts slighter modifications to each block, which leads to significant improvement of visual quality for the decrypted image. The receiver can easily decrypt the marked, encrypted image using the encryption key, and then, through the data-hiding key and an adaptive evaluation function of smoothness characteristic along the isophote direction, secret data can be extracted from the decrypted image, and the original image can further be recovered successfully. Experimental results demonstrate the effectiveness of the proposed scheme. © 2015 Elsevier Inc. All rights reserved.


Li Y.,Shanghai Key Laboratory of Modern Optical Systems | Cai B.,Shanghai Key Laboratory of Modern Optical Systems | Zhu Y.,Shanghai Key Laboratory of Modern Optical Systems
Optics Letters | Year: 2015

A terahertz (THz) anti-reflective structure on a polystyrene layer was fabricated by using a handmade metallic mold comprising a bunch of Chinese acupuncture needles. Polystyrene was spin-coated onto a silicon substrate and then deformed by the mold via a hot-embossing process. The deformed layer yielded gradient refractive index profiles on the substrate. Compared with a common single antireflective layer, we observed an increase of ∼20% in the transmittance. We also observed broader bandwidth properties compared with the single layer structure. The process imposes no substrate limiting, i.e., it can be applied onto various THz device surfaces for antireflection purpose. © 2015 Optical Society of America.


Gu F.,Shanghai Key Laboratory of Modern Optical Systems | Gu F.,Zhejiang University | Zeng H.,Shanghai Key Laboratory of Modern Optical Systems | Zeng H.,East China Normal University | And 2 more authors.
Optics Letters | Year: 2013

We demonstrated a general approach for plasmonic sensing using metal single nanowires based on an evanescent coupling technique, where light was efficiently launched into and picked up from the metal nanowires using silica fiber tapers. A high amplitude sensitivity of ∼13 dB to 1.2% hydrogen was obtained using palladium-coated Au nanowires for hydrogen sensing, and a fast response of ∼5 ms was obtained using a polyacrylamide filmsupported Ag nanowire for relative humidity sensing. Our results may help develop metal nanowire-based plasmonic sensors. © 2013 Optical Society of America.


Chen L.,Shanghai Key Laboratory of Modern Optical Systems | Chen L.,Nanjing Southeast University | Gao C.,Shanghai Key Laboratory of Modern Optical Systems | Xu J.,Shanghai Key Laboratory of Modern Optical Systems | And 3 more authors.
Optics Letters | Year: 2013

Electromagnetically induced transparency (EIT)-like transmission was demonstrated in terahertz asymmetric parallel plate waveguides with two identical cavities. By shifting the position of the bottom cavity from the symmetric position in the propagation direction, both the phases of the propagating wave at resonances and the coupling strengths between two cavities are changed, resulting in exciting the additional asymmetric resonance and manipulating the detuning of two different resonant frequencies. The transparent peak between two resonances comes from the cancelation of symmetric and asymmetric resonances. We also use the physical picture of excitation of quasidark mode to explain this EIT-like transmission, which is similar to the metamaterial systems. © 2013 Optical Society of America.


Wang L.,Shanghai Key Laboratory of Modern Optical Systems | Wei G.,Shanghai Key Laboratory of Modern Optical Systems | Shu H.,Donghua University
Neurocomputing | Year: 2013

In this paper, the H∞ state estimation problem is investigated for a class of discrete-time complex networks with randomly occurring phenomena. The proposed randomly occurring phenomena include both probabilistic missing measurements and randomly occurring coupling delays which are described by two random variable sequences satisfying individual probability distributions, respectively. Rather than the common Lipschitz-type function, a more general sector-like nonlinear function is employed to characterize the nonlinearities in the networks. The purpose of the addressed H∞ state estimation problem is to design a state estimator such that, for all admissible nonlinear disturbances, missing measurements as well as coupling delays, the dynamics of the augmented systems is guaranteed to be exponentially mean-square stable and attenuated to a given H∞ performance level. By constructing a novel Lyapunov-Krasovskii functional and utilizing convex optimization method as well as Kronecker product, we derive the sufficient conditions under which the desired state estimator exists. An illustrative example is exploited to show the effectiveness of the proposed state estimation scheme. © 2013 Elsevier B.V.


Ding D.,Shanghai Key Laboratory of Modern Optical Systems | Wang Z.,Brunel University | Shen B.,Donghua University | Dong H.,Northeast Petroleum University
Automatica | Year: 2015

In this paper, the envelope-constrained H∗ filtering problem is investigated for a class of discrete time-varying stochastic systems over a finite horizon. The system under consideration involves fading measurements, randomly occurring nonlinearities (RONs) and mixed (multiplicative and additive) noises. A novel envelope-constrained performance criterion is proposed to better quantify the transient dynamics of the filtering error process over the finite horizon. The purpose of the problem addressed is to design a time-varying filter such that both the H∗ performance and the desired envelope constraints are achieved at each time step. By utilizing the stochastic analysis techniques combined with the ellipsoid description on the estimation errors, sufficient conditions are established in the form of recursive matrix inequalities (RMIs) reflecting both the envelope information and the desired H∗ performance index. The filter gain matrix is characterized by means of the solvability of the deduced RMIs. Finally, a simulation example is provided to show the effectiveness of the proposed filtering design scheme. © 2015 Elsevier Ltd.


Wang L.,Shanghai Key Laboratory of Modern Optical Systems | Wei G.,Shanghai Key Laboratory of Modern Optical Systems | Li W.,University of Shanghai for Science and Technology
Neurocomputing | Year: 2014

In this paper, the H∞ synchronization control problem is investigated for a class of dynamical networks with randomly varying nonlinearities. The time varying nonlinearities of each node are modelled to be randomly switched between two different nonlinear functions by utilizing a Bernoulli distributed variable sequence specified by a randomly varying conditional probability distribution. A probability-dependent gain scheduling method is adopted to handle the time varying characteristic of the switching probability. Attention is focused on the design of a sequence of gain-scheduled controllers such that the controlled networks are exponentially mean-square stable and the H∞ synchronization performance is achieved in the simultaneous presence of randomly varying nonlinearities and external energy bounded disturbances. Except for constant gains, the desired controllers are also composed of time varying parameters, i.e., the time varying switching probability and therefore less conservatism will be resulted comparing with traditional controllers. In virtue of semi-definite programming method, controller parameters are derived in terms of the solutions to a series of linear matrix inequalities (LMIs) that can be easily solved by the Matlab toolboxes. Finally, a simulation example is exploited to illustrate the effectiveness of the proposed control strategy. © 2014 Elsevier B.V.


Ding D.,Shanghai Key Laboratory of Modern Optical Systems | Wang Z.,Brunel University | Shen B.,Donghua University | Wei G.,Shanghai Key Laboratory of Modern Optical Systems
Automatica | Year: 2015

This paper is concerned with the event-triggered consensus control problem for a class of discrete-time stochastic multi-agent systems with state-dependent noises. A novel definition of consensus in probability is proposed to better describe the dynamics of the consensus process of the addressed stochastic multi-agent systems. The measurement output available for the controller is not only from the individual agent but also from its neighboring ones according to the given topology. An event-triggered mechanism is adopted with hope to reduce the communication burden, where the control input on each agent is updated only when a certain triggering condition is violated. The purpose of the problem under consideration is to design both the output feedback controller and the threshold of the triggering condition such that the closed-loop system achieves the desired consensus in probability. First of all, a theoretical framework is established for analyzing the so-called input-to-state stability in probability (ISSiP) for general discrete-time nonlinear stochastic systems. Within such a theoretical framework, some sufficient conditions on event-triggered control protocol are derived under which the consensus in probability is reached. Furthermore, both the controller parameter and the triggering threshold are obtained in terms of the solution to certain matrix inequalities involving the topology information and the desired consensus probability. Finally, a simulation example is utilized to illustrate the usefulness of the proposed control protocol. © 2015 Elsevier Ltd.


Zhang D.,Shanghai Key Laboratory of Modern Optical Systems | Zhang F.,Shanghai Key Laboratory of Modern Optical Systems
Optik | Year: 2014

According to encrypting principles of digital images, integrating the characteristic of JPEG image, and using discrete chaotic sequence, this paper has studied encryption and decryption of JPEG image, and has compared and analyzed the corresponding relations between the encryption and decryption effects and their security of two different encrypting schemes of the JPEG image chaotic encryption studied by this paper. In a basic unit of an 8 × 8 data block, image encryption and decryption not only are fast, but also match with JPEG format. The JPEG image encryption can meet the security requirement of the storage and transmission of JPEG images in some common application occasions, and provides an effective and feasible way of encrypting JPEG images. © 2013 Elsevier GmbH.


Fang L.,Shanghai Key Laboratory of Modern Optical Systems | Jia H.,Shanghai Key Laboratory of Modern Optical Systems
Optics Communications | Year: 2014

Coupling characteristics of core higher-order modes LP0m with optical fiber gratings written in step-index multimode fiber (MMF) and their application in mode-division multiplexing (MDM) transmission are presented and analyzed in this article. Several long-period fiber gratings (LPFGs) cascaded in one MMF can realize conversion between any two core modes, HE1m (m=1,2,3,.,6) in other words and scalar mode LP0m, in mode order from low to high. These eigenmodes supported in fiber as independent data channels are theoretically proposed to be multiplexed in one MMF by the combination of LPFGs and fiber Bragg gratings (FBGs) united with optical circulators as both multiplexers and de-multiplexers. This method of flexible mode conversion using optical gratings can be practically significant on fiber communication as a mode-selective converter. © 2014 Elsevier B.V.

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