1,075 research outputs found
Vector modulation instability induced by vacuum fluctuations in highly birefringent fibers in the anomalous dispersion regime
We report a detailed experimental study of vector modulation instability in
highly birefringent optical fibers in the anomalous dispersion regime. We prove
that the observed instability is mainly induced by vacuum fluctuations. The
detuning of the spectral peaks agrees with linear perturbation analysis. The
exact shape of the spectrum is well reproduced by numerical integration of
stochastic nonlinear Schrodinger equations describing quantum propagation.Comment: 11 pages, 4 figures, to be published in Optics Letter
Periodic waves in bimodal optical fibers
We consider coupled nonlinear Schrodinger equations (CNLSE) which govern the
propagation of nonlinear waves in bimodal optical fibers. The nonlinear
transform of a dual-frequency signal is used to generate an ultra-short-pulse
train. To predict the energy and width of pulses in the train, we derive three
new types of travelling periodic-wave solutions, using the Hirota bilinear
method. We also show that all the previously reported periodic wave solutions
of CNLSE can be derived in a systematic way, using the Hirota method.Comment: 10 pages with 2 figures. "Optics Communications, in press
Tunable Modulational Instability Sidebands via Parametric Resonance in Periodically Tapered Optical Fibers
We analyze the modulation instability induced by periodic variations of group
velocity dispersion and nonlinearity in optical fibers, which may be
interpreted as an analogue of the well-known parametric resonance in mechanics.
We derive accurate analytical estimates of resonant detuning, maximum gain and
instability margins, significantly improving on previous literature on the
subject. We also design a periodically tapered photonic crystal fiber, in order
to achieve narrow instability sidebands at a detuning of 35 THz, above the
Raman maximum gain peak of fused silica. The wide tunability of the resonant
peaks by variations of the tapering period and depth will allow to implement
sources of correlated photon pairs which are far-detuned from the input pump
wavelength, with important applications in quantum optics.Comment: 15 pages, 7 figure
1073-143 Physiological assessment of coronary artery stenosis using transthoracic doppler echocardiography at rest: Comparison of flow velocity pattern analysis with exercise thallium SPECT
Formation and Propagation of Matter Wave Soliton Trains
Attraction between atoms in a Bose-Einstein-Condensate renders the condensate
unstable to collapse. Confinement in an atom trap, however, can stabilize the
condensate for a limited number of atoms, as was observed with 7Li, but beyond
this number, the condensate collapses. Attractive condensates constrained to
one-dimensional motion are predicted to form stable solitons for which the
attractive interactions exactly compensate for the wave packet dispersion. Here
we report the formation or bright solitons of 7Li atoms created in a quasi-1D
optical trap. The solitons are created from a stable Bose-Einstein condensate
by magnetically tuning the interactions from repulsive to attractive. We
observe a soliton train, containing many solitons. The solitons are set in
motion by offsetting the optical potential and are observed to propagate in the
potential for many oscillatory cycles without spreading. Repulsive interactions
between neighboring solitons are inferred from their motion
Modulational Instability in Equations of KdV Type
It is a matter of experience that nonlinear waves in dispersive media,
propagating primarily in one direction, may appear periodic in small space and
time scales, but their characteristics --- amplitude, phase, wave number, etc.
--- slowly vary in large space and time scales. In the 1970's, Whitham
developed an asymptotic (WKB) method to study the effects of small
"modulations" on nonlinear periodic wave trains. Since then, there has been a
great deal of work aiming at rigorously justifying the predictions from
Whitham's formal theory. We discuss recent advances in the mathematical
understanding of the dynamics, in particular, the instability of slowly
modulated wave trains for nonlinear dispersive equations of KdV type.Comment: 40 pages. To appear in upcoming title in Lecture Notes in Physic
Analytical model and experimental verification of the critical power for modulation instability in optical fibers
Modulational instability in a fiber soliton ring laser induced by periodic dispersion variation
Modulational instability with sideband generation is experimentally observed in a passively mode-locked fiber soliton ring laser. We show numerically that this modulational instability is induced by the periodic dispersion variation experienced by light circulating in the laser cavity. Modulational instability caused by cross-phase-modulation is also observed in the laser and confirmed numerically
Two-way habitat use between reefs and open ocean in adult greater amberjack: evidence from biologging data
We investigated the relationships between vertical movements and both oceanographic features and physiological factors in greater amberjack Seriola dumerili, which is a reef-associated predator in the East China Sea. S. dumerili in the coastal waters of eastern Taiwan were equipped with archival tags or pop-up satellite archival tags that recorded depth and temperature, resulting in a dataset covering a total of 1331 d from 12 individuals. To classify the vertical movement patterns of S. dumerili, we performed a hierarchical cluster analysis for the depth profile. We observed multiple vertical movement patterns. Around topographic features, S. dumerili showed short-step dives (averaging < 35 m) during both the daytime and nighttime. In contrast, S. dumerili in offshore areas showed diel vertical movements. S. dumerili occasionally performed frequent dives to approximately 150 m throughout the day. These movements may be related to foraging behaviors associated with changes in water depth. We further analyzed the response of the peri-toneal cavity temperature to variations in the ambient temperature in 7 S. dumerili with archival tags. The peritoneal cavity temperatures fluctuated according to the ambient temperature changes, indicating that the vertical movement of S. dumerili is limited by physiological con-straints for the maintenance of body temperature. Together, our results indicate that the vertical movement of S. dumerili may be affected by the trade-off between foraging and thermoregulation
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