The Experts below are selected from a list of 25824 Experts worldwide ranked by ideXlab platform
Alejandro Yacomotti - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Mode scattering in strongly coupled photonic crystal nanolasers
European Quantum Electronics Conference, 2017Co-Authors: M Marconi, J Javaloyes, F Raineri, A Levenson, Alejandro YacomottiAbstract:In semiconductor-coupled micro and nano-cavities, the combination between tight light confinement and high optical nonlinearities open up new routes for the study of light-matter interaction in non-equilibrium driven dissipative systems. Even at the semiclassical level, coupled cavities may display a wide range of rich nonlinear dynamical phenomena such as instabilities and bifurcations [1]. Mode competition is at the heart of multiMode laser dynamics, and may occur when different Modes share the same gain medium. Mode switching (MS) and bistability have been observed in standard microcavity systems, such as vertical-cavity surface-emitting lasers (VCSELs) [2], micropillar lasers [3], semiconductor ring lasers [4]. These mechanisms usually rely on symmetric cross-gain saturation effects [4]. However, Mode interaction in semiconductor cavities may also be Asymmetric, resulting from stimulated scattering due to a dynamic carrier population grating in the gain medium, which oscillates at the beat note frequency between adjacent cavity Modes. Such an Asymmetric interaction enables energy transfer from the laser Mode at the blue side of the spectrum to the Mode at the red side [5].
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Asymmetric Mode scattering in strongly coupled photonic crystal nanolasers
Optics Letters, 2016Co-Authors: M Marconi, J Javaloyes, F Raineri, J A Levenson, Alejandro YacomottiAbstract:We investigate the basic mechanism of nonlinear Mode competition in two semiconductor-coupled nanocavities operating in the laser regime. For this, we study energy transfer between bonding (in-phase) and anti-bonding (out-of-phase) Modes of the system formed by two strongly coupled photonic crystal nanolasers. We experimentally observe Mode switching from the blue-detuned to the red-detuned Mode as the pump power is increased. A semi-classical description in terms of mean-field equations allows us to explain this phenomenon as stimulated scattering due to carrier population oscillations in the cavities at the Mode splitting frequency. We predict such Asymmetrical Mode interaction to be universal in arrays of optically coupled semiconductor micro and nanocavities.
Huihuang Zhong - One of the best experts on this subject based on the ideXlab platform.
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analysis on the mechanism of pulse shortening in an x band triaxial klystron amplifier due to the Asymmetric Mode competition
Physics of Plasmas, 2016Co-Authors: Jun Zhang, Yongjie Xie, Yi Zhang, Zehua Wang, Xiaofeng Zhou, Jianhui Zhu, Huihuang ZhongAbstract:Asymmetric Mode competitions are observed in the design of an X-band triaxial klystron amplifier with an Asymmetric input cavity, and the generation mechanism of the Asymmetric Mode competition is analyzed in the paper. The results indicate that the Asymmetric Modes are excited in the buncher cavity. The Asymmetric Mode (coaxial TM612 Mode) in the buncher cavity with the highest shunt impedance can start up first among the Asymmetric Modes with negative beam loading conductance. The coupling of the corresponding coaxial TE Mode between the buncher and input cavity exacerbates the start oscillation of the Asymmetric Mode competition. The rationality of the analysis is demonstrated by cutting off the propagation of the corresponding coaxial TE Modes between the buncher cavity and the input cavity, and the Asymmetric Mode competitions are thoroughly suppressed by specially designed reflectors and lossy material. In simulation, a microwave with a power of 1.28 GW and a frequency of 9.375 GHz is generated, and the extraction efficiency and the gain are 34.5% and 41.5 dB, respectively.
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design and experimental demonstration of a long pulse x band triaxial klystron amplifier with an Asymmetric input cavity
IEEE Electron Device Letters, 2016Co-Authors: Jun Zhang, Huihuang Zhong, Qiang Zhang, Lei YangAbstract:A triaxial klystron amplifier (TKA) with an Asymmetric input cavity is designed to generate a long-pulse high power microwave at X-band. The input microwave is equally divided into two parts and then injected into an Asymmetric input cavity to keep the axial electric field azimuthally symmetric in the input cavity. An Asymmetric Mode competition resulting in a pulse shortening on the output power is observed in a TKA with an Asymmetric input cavity. The analysis indicates that the Asymmetric Mode is excited and amplified in the buncher cavity for the coaxial waveguide cannot cut off the corresponding Asymmetric TE Mode. By a reflector with high reflection coefficients both to the Asymmetric Mode and the TEM Mode, the Asymmetric Mode competition is effectively suppressed in 3-D particle-in-cell simulation. The designed TKA is demonstrated by the experiment, in which a microwave with pulse duration of 100 ns, a power of 240 MW, and a gain of $\sim 34$ dB is generated.
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simulation investigation of a ku band radial line oscillator operating at low guiding magnetic field
Physics of Plasmas, 2014Co-Authors: Fangchao Dang, Huihuang Zhong, Xiaoping Zhang, Yangmei Li, Zumin QiAbstract:A novel radial line oscillator operating at Ku-band with low guiding magnetic field is proposed in this paper. By using an oversized radial structure, the power handling capacity is enhanced significantly. Based on the small-signal theory, the π/2 Mode in radial TM{sub 01} Mode is selected as the working Mode. Furthermore, a radial uniform guiding magnetic field, made up of four solenoids, is designed. As indicated in 2.5-dimensional fully electromagnetic particle-in-cell simulation, high power microwaves with a power of 2.2 GW and a frequency of 14.25 GHz are generated with over 40% efficiency when the electron beam voltage is 300 kV, the beam current 18 kA, and the guiding magnetic field is only 0.6 T. There is no angular non-Asymmetric Mode discovered in three-dimensional simulation.
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Asymmetric Mode competition in a relativistic backward wave oscillator with a coaxial slow wave structure
Applied Physics Letters, 2010Co-Authors: Huihuang Zhong, Jun Zhang, Baoliang Qian, Lie Liu, Liang Gao, Chengwei YuanAbstract:The initial experimental results of an L-band relativistic backward wave oscillator with a coaxial slow-wave structure are presented. The Asymmetric-Mode-competition mechanism in the device is investigated theoretically and experimentally. It is shown that the diode voltage, guiding-magnetic field, and concentricity play a key role in the suppression and excitation of the Asymmetric-Mode (coaxial quasi-TE11 Mode). In the experiments, the Asymmetric-Mode with a frequency of 2.05 GHz is suppressed and excited, which is in good agreement with the theoretical results.
Alper Erturk - One of the best experts on this subject based on the ideXlab platform.
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phononic crystal luneburg lens for omnidirectional elastic wave focusing and energy harvesting
Applied Physics Letters, 2017Co-Authors: F L Degertekin, Alper ErturkAbstract:We explore a phononic crystal Luneburg lens through design, fabrication, and analysis for omnidirectional elastic wave focusing and enhanced energy harvesting both numerically and experimentally. The proposed lens is formed using hexagonal unit cells with blind holes of different diameters, which are determined according to the Luneburg lens refractive index distribution obtained by finite-element simulations of the lowest Asymmetric Mode Lamb wave band structure. Wave simulations are performed numerically under plane wave excitation from a line source, and focusing is observed at the opposite border of the lens with respect to the incident wave direction. Numerically simulated elastic wave focusing results are validated through a set of experiments. Omnidirectionality is demonstrated by testing the lens under plane wave excitation for different angles of incidence. With piezoelectric energy harvesters located at the boundary of the phononic crystal Luneburg lens, more than an order of magnitude larger po...
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gradient index phononic crystal lens based enhancement of elastic wave energy harvesting
Applied Physics Letters, 2016Co-Authors: F L Degertekin, Alper ErturkAbstract:We explore the enhancement of structure-borne elastic wave energy harvesting, both numerically and experimentally, by exploiting a Gradient-Index Phononic Crystal Lens (GRIN-PCL) structure. The proposed GRIN-PCL is formed by an array of blind holes with different diameters on an aluminum plate, where the blind hole distribution is tailored to obtain a hyperbolic secant gradient profile of refractive index guided by finite-element simulations of the lowest Asymmetric Mode Lamb wave band diagrams. Under plane wave excitation from a line source, experimentally measured wave field validates the numerical simulation of wave focusing within the GRIN-PCL domain. A piezoelectric energy harvester disk located at the first focus of the GRIN-PCL yields an order of magnitude larger power output as compared to the baseline case of energy harvesting without the GRIN-PCL on the uniform plate counterpart.
M Marconi - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Mode scattering in strongly coupled photonic crystal nanolasers
European Quantum Electronics Conference, 2017Co-Authors: M Marconi, J Javaloyes, F Raineri, A Levenson, Alejandro YacomottiAbstract:In semiconductor-coupled micro and nano-cavities, the combination between tight light confinement and high optical nonlinearities open up new routes for the study of light-matter interaction in non-equilibrium driven dissipative systems. Even at the semiclassical level, coupled cavities may display a wide range of rich nonlinear dynamical phenomena such as instabilities and bifurcations [1]. Mode competition is at the heart of multiMode laser dynamics, and may occur when different Modes share the same gain medium. Mode switching (MS) and bistability have been observed in standard microcavity systems, such as vertical-cavity surface-emitting lasers (VCSELs) [2], micropillar lasers [3], semiconductor ring lasers [4]. These mechanisms usually rely on symmetric cross-gain saturation effects [4]. However, Mode interaction in semiconductor cavities may also be Asymmetric, resulting from stimulated scattering due to a dynamic carrier population grating in the gain medium, which oscillates at the beat note frequency between adjacent cavity Modes. Such an Asymmetric interaction enables energy transfer from the laser Mode at the blue side of the spectrum to the Mode at the red side [5].
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Asymmetric Mode scattering in strongly coupled photonic crystal nanolasers
Optics Letters, 2016Co-Authors: M Marconi, J Javaloyes, F Raineri, J A Levenson, Alejandro YacomottiAbstract:We investigate the basic mechanism of nonlinear Mode competition in two semiconductor-coupled nanocavities operating in the laser regime. For this, we study energy transfer between bonding (in-phase) and anti-bonding (out-of-phase) Modes of the system formed by two strongly coupled photonic crystal nanolasers. We experimentally observe Mode switching from the blue-detuned to the red-detuned Mode as the pump power is increased. A semi-classical description in terms of mean-field equations allows us to explain this phenomenon as stimulated scattering due to carrier population oscillations in the cavities at the Mode splitting frequency. We predict such Asymmetrical Mode interaction to be universal in arrays of optically coupled semiconductor micro and nanocavities.
Addepalli V. N. Krishna - One of the best experts on this subject based on the ideXlab platform.
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a big data security mechanism based on fully homomorphic encryption using cubic spline curve public key cryptography
Journal of Information and Optimization Sciences, 2018Co-Authors: Addepalli V. N. KrishnaAbstract:In this work, a Cubic spline curve based Asymmetric Mode encrypting data is used for Fully Homomorphic encryption on Big–Data. A steady state, one dimensional equation is integrated over a control ...
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cubic spline curve public key cryptography
Journal of Discrete Mathematical Sciences and Cryptography, 2017Co-Authors: Addepalli V. N. Krishna, Addepalli Hari NarayanaAbstract:AbstractIn this work, a cubic spline curve is considered for Asymmetric Mode encrypting data. A Cubicspline curve is used to generate a set of points under initial known boundary conditions. This set of points is considered as generator points. Given the field, known the generator points, considering for some time and space steps and for a considered private key, Public key will be generated based on Discrete Logarithm problem. Thus for a set of public and private keys, data can be transmitted securely with features like Authenticity of users, Security & Confidentiality of data transmitted.Going by the construction of the algorithm, Encryption is being done on blocks of data for which it consumes less computing resources. Going by complexity of the algorithm, the key length needed is about 120 bit lengths to provide sufficient strengths against cryptoanalysis.
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fully homomorphic encryption with matrix based digital signature standard
Journal of Discrete Mathematical Sciences and Cryptography, 2017Co-Authors: Addepalli V. N. Krishna, Addepalli Hari Narayana, Madhura K VaniAbstract:AbstractIn this work, a novel mechanism is considered for Asymmetric Mode encrypting data. A generator matrix is used to generate a field with a large prime number. The generator matrix, prime number and ternary vector are used as global variables. Those global variables are used to calculate public key and sub keys. Using the Global Variables and Private key, a Digital signature algorithm is proposed which supports the feature like Authenticity of users. The mechanism can also be used in Homomorphic Encryption where computations to be carried out on cipher text and generate an encrypted result which, when decrypted, matches the result of operations performed on the plaintext.
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window method based cubic spline curve public key cryptography
International Journal of Electronics and Information Engineering, 2016Co-Authors: Addepalli V. N. Krishna, Addepalli Hari Narayana, Madhura K VaniAbstract:In this work, a cubic spline curve is considered for Asymmetric Mode encrypting data. A steady state, one dimensional equation is integrated over a control volume. The derivatives of above equation form piece wise linear profile, which leads to discretization equation with corresponding weights. These weights are initially solved to generate global variables. Those global variables are used to calculate public key which in turn use the ElGamal Mode of encryption. The proposed algorithm supports the features like Authenticity of users, Security & Confidentiality of data transmitted. Going by the construction of the algorithm, Encryption is being done on blocks of data for which it consumes less computing resources. Going by complexity of the algorithm, the key length needed is about 120 bit length to provide sufficient strengths against cryptanalysis.
