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He Y.,Guangdong Polytechnic Normal University | Malomed B.A.,Tel Aviv University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We demonstrate the existence of two species of stable bright solitons, fundamental and dipole, in one-dimensional self-defocusing nonlocal media, with the local value of nonlinearity coefficient having one or several minima and growing at any rate faster than |x| at large values of coordinate x. The model can be derived for a slab optical waveguide with thermal nonlinearity. The most essential difference from the local counterpart of this system is the competition between two different spatial scales, one determining the modulation pattern of the nonlinearity coefficient and the other being the correlation length of the nonlocality. The competition is explicitly exhibited by an analytically obtained asymptotic form of generic solutions. Particular exact solutions are found analytically, and full soliton families are constructed in a numerical form. The multichannel settings, with two or three local minima of the nonlinearity coefficient, are considered here for both local and nonlocal models of the present type. States with multiple solitons launched into different channels are stable if the spacing between them exceeds a certain minimum value. A regime of stable Josephson oscillations of solitons between parallel channels is reported too. © 2013 American Physical Society. Source


Xie X.,Sun Yat Sen University | Chen Y.,Guangdong Polytechnic Normal University | Yang K.,Sun Yat Sen University | Zhou J.,Sun Yat Sen University
Physical Review Letters | Year: 2014

The resolution limit of far-field optical microscopy is reexamined with a full vectorial theoretical analysis. A highly symmetric excitation optical field and optimized detection scheme are proposed to harness the total point-spread function for a microscopic system. Spatial resolution of better than 1/6λ is shown to be obtainable, giving rise to a resolution better than 100 nm with visible light excitation. The experimental measurement is applied to examine nonfluorescent samples. A lateral resolution of 1/5λ is obtained in truly far-field optical microscopy with a working distance greater than ∼500λ. Comparison is made for the far-field microscopic measurement with that of a nearfield scanning optical microscopy, showing that the proposed scheme provides a better image quality. © 2014 American Physical Society. Source


Lin X.-S.,South China Normal University | Lin X.-S.,Guangdong Polytechnic Normal University | Lan S.,South China Normal University
Plasmonics | Year: 2013

We investigate theoretically and numerically the resonant transmission through side-coupled metallic grooves. In the framework of coupled mode theory (CMT), a single metallic groove can be considered as a lossy optical resonator and two metallic grooves coupled via tunneling effect can be treated as a second-order cascade resonator. The relationship between the transmission lineshape of the coupled grooves and the cross-coupling between the grooves is analyzed by CMT. It is found that a flat-on-top lineshape can be obtained when the cross-coupling is equal to the total decay rate of the groove mode. Predictions based on the CMT analysis are in good agreement with the simulation results based on the finite-difference time-domain technique. © 2012 Springer Science+Business Media, LLC. Source


Hu R.,Guangdong Polytechnic Normal University
Applied Mathematics and Information Sciences | Year: 2012

Providing stable compositions of Wireless Sensor Network Service (WSNS) is a challenging issue since the data stream architect often has only a limited control over the stability of the composed services. The architect can instead achieve stability by properly planning the data stream architecture. In this paper, we propose a formal approach which allows a data stream architect to perform stability analysis of WSNS-based security service. The approach exploits the concept of stability methods to evaluate the stability function of a wide class of data streams. The effect of the approach and the operation of the tool are demonstrated with respect to a case study of a business security infrastructure realized by simple security services. © 2012 NSP Natural Sciences Publishing Cor. Source


Yin C.,South China Normal University | He Y.,Guangdong Polytechnic Normal University | Li H.,Guangzhou University | Xie J.,Foshan University
Optics Express | Year: 2012

We study the solitons in parity-time symmetric potential in the medium with spatially modulated nonlocal nonlinearity. It is found that the coefficient of the spatially modulated nonlinearity and the degree of the uniform nonlocality can profoundly affect the stability of solitons. There exist stable solitons in low-power regionand unstable solitons in high-power region. In the unstable casesthe solitons exhibit jump from the original site to the next oneand they can continue the motion into the other lattices. The region of the stable soliton can be expanded by increasing the coefficient of the modulated nonlocality. Finallycritical amplitude of the imaginary part of the linear PT lattices is obtainedabove which solitons are unstable and decay immediately. © 2012 Optical Society of America. Source

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