Ref HAL: hal-00628026_v1
DOI: 10.1103/PhysRevA.83.043836
WoS: 000290107500016
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10 Citations
Résumé:

A method is proposed to generate and study the dynamics of spatial light solitons in a birefringent medium with quadratic nonlinearity. Although no analytical expression for propagating solitons has been obtained, our numerical simulations show the existence of stable localized spatial solitons in the frequency forbidden band gap of the medium. The dynamics of these objects is quite rich and manifests for instance elastic reflections, or inelastic collisions where two solitons merge and propagate as a single solitary wave. We derive the dynamics of the slowly varying envelopes of the three fields (second harmonic pump and two-component signal) and study this new system theoretically. We show that it does present a threshold for nonlinear supratransmission that can be calculated from a series expansion approach with a very high accuracy. Specific physical implications of our theoretical predictions are illustrated on LiGaTe2 (LGT) crystals. Once irradiated by a cw laser beam of 10 mu m wavelength, at an incidence beyond the extinction angle, such crystals will transmit light, in the form of spatial solitons generated in the nonlinear regime above the nonlinear supratransmission threshold.

Ref HAL: hal-00628025_v1
DOI: 10.1063/1.3604797
WoS: 000292335700087
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11 Citations
Résumé:

We report direct measurements of average vibration energy in a high frequency flexural resonance mode achieved via an-harmonic elastic coupling to a fundamental vibration mode of a nanomechanical resonator. The second order coupling effect produces a frequency shift of the read-out mode as a function of the mean square of the excitation amplitude of the high order mode. We measure frequency shifts at the lowest driving amplitudes, down to the noise floor of the experimental setup. With implementation of existing ultra-sensitive amplifiers, the reported technique will enable direct measurements of quantized energy transitions in low-thermal occupation number nanomechanical resonators.

Ref HAL: hal-00819816_v1
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Résumé:

Aucun

Ref HAL: hal-00534890_v1
DOI: 10.1103/PhysRevA.82.053604
WoS: 000283838000009
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38 Citations
Résumé:

We study the effect of discrete breathers (DBs) on the transfer of a Bose-Einstein condensate (BEC) in an optical lattice using the discrete nonlinear Schrödinger equation. In previous theoretical (primarily numerical) investigations of the dynamics of BECs in leaking optical lattices, collisions between a DB and a lattice excitation, e.g., a moving breather (MB) or phonon, were studied. These collisions led to the transmission of a fraction of the incident (atomic) norm of the MB through the DB, while the DB can be shifted in the direction of the incident lattice excitation. Here we develop an analytic understanding of this phenomenon, based on the study of a highly localized system—namely, a nonlinear trimer—which predicts that there exists a total energy threshold of the trimer, above which the lattice excitation can trigger the destabilization of the DB and that this is the mechanism leading to the movement of the DB. Furthermore, we give an analytic estimate of upper bound to the norm that is transmitted through the DB. We then show numerically that a qualitatively similar threshold exists in extended lattices. Our analysis explains the results of the earlier numerical studies and may help to clarify functional operations with BECs in optical lattices such as blocking and filtering coherent (atomic) beams.

Ref HAL: hal-00510988_v1
PMID 20868047
DOI: 10.1103/PhysRevLett.105.074101
WoS: 000280811700003
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23 Citations
Résumé:

A method is proposed to solve the challenging problem of determining the supratransmission threshold (onset of insability of harmonic boundary driving inside a band gap) in multicomponent non-integrable nonlinear systems. It is successfully applied to the degenerate three-wave resonant interaction in a birefrigent quadratic medium where the process generates spatial gap solitons. No analytic expression is known for such nonlinear solitary waves showing the broad applicability of the method to nonlinear systems.

Commentaires: http://arxiv.org/abs/1008.1920

Ref HAL: hal-00491003_v1
Ref Arxiv: 1006.0943
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

We study the stability of a stationary discrete breather (DB) on a nonlinear trimer in the framework of the discrete nonlinear Schrödinger equation (DNLS). In previous theoretical investigations of the dynamics of Bose-Einstein condensates in leaking optical lattices, collisions between a DB and a lattice excitation, e.g. a moving breather (MB) or phonon, were studied. These collisions lead to the transmission of a fraction of the incident (atomic) norm of the MB through the DB, while the DB can be shifted in the direction of the incident lattice excitation. Here we show that there exists a total energy threshold of the trimer, above which the lattice excitation can trigger the destabilization of the DB and that this is the mechanism leading to the movement of the DB. Furthermore, we give an analytic estimate of upper bound to the norm that is transmitted through the DB. Our analysis explains the results of the earlier numerical studies and may help to clarify functional operations with BECs in optical lattices such as blocking and filtering coherent (atomic) beams.

Commentaires: 8 pages, 5 figures

Ref HAL: hal-00430445_v1
Ref Arxiv: 0903.2081
DOI: 10.1063/1.3132088
WoS: 000266500100089
Ref. & Cit.: NASA ADS
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3 Citations
Résumé:

We propose a general one-dimensional {\em continuous} formulation to analyzethe vibrational modes of antenna-like nanomechanical resonators consisting oftwo symmetric arrays of cantilevers affixed to a central nano-beam. Thecantilever arrays can have arbitrary density and length profile along the beam.We obtain the secular equation that allows for the determination of theirfrequency spectrum and illustrate the results on the particular examples ofstructures with constant or alternating cantilever length profiles. We showthat our analytical results capture the vibration spectrum of such resonatorsand elucidate key relationships that could prove advantageous for experimentaldevice performance. Furthermore, using a perturbative approach to treat thenonlinear and dissipative dynamics of driven structures, we analyze theanharmonic coupling between two specific widely spaced modes of thecoupled-element device, with direct application to experiments.