148 research outputs found
Few-cycle optical solitary waves in nonlinear dispersive media
We study the propagation of few-cycle optical solitons in nonlinear media with an anomalous, but otherwise arbitrary, dispersion and a cubic nonlinearity. Our approach does not derive from the slowly varying envelope approximation. The optical field is derived directly from Maxwell's equations under the assumption that generation of the third harmonic is a nonresonant process or at least cannot destroy the pulse prior to inevitable linear damping. The solitary wave solutions are obtained numerically up to nearly single-cycle duration using the spectral renormalization method originally developed for the envelope solitons. The theory explicitly distinguishes contributions between the essential physical effects such as higher-order dispersion, self-steepening, and backscattering, as well as quantifies their influence on ultrashort optical solitons
Sasa-Satsuma hierarchy of integrable evolution equations
We present the infinite hierarchy of Sasa-Satsuma evolution equations. The corresponding Lax pairs are given, thus proving its integrability. The lowest order member of this hierarchy is the nonlinear Schrödinger equation, while the next one is the Sasa-Satsuma equation that includes third-order terms. Up to sixth-order terms of the hierarchy are given in explicit form, while the provided recurrence relation allows one to explicitly write all higher-order terms. The whole hierarchy can be combined into a single general equation. Each term in this equation contains a real independent coefficient that provides the possibility of adapting the equation to practical needs. A few examples of exact solutions of this general equation with an infinite number of terms are also given explicitly.The authors gratefully acknowledge the support of the Australian Research Council (Discovery Projects
DP140100265 and DP150102057) and support from the Volkswagen Stiftung. N.A. is a recipient of the Alexander von Humboldt Award. U.B. acknowledges support by the German Research Foundation in the framework of the Collaborative Research Center 787 “Semiconductor Nanophotonics” under project B5. Sh.A. acknowledges support of the German Research Foundation under Project No. 389251150
Infinite hierarchy of nonlinear Schrödinger equations and their solutions
We study the infinite integrable nonlinear Schrödinger equation hierarchy beyond the Lakshmanan-Porsezian-Daniel equation which is a particular (fourth-order) case of the hierarchy. In particular, we present the generalized Lax pair and generalized soliton solutions, plane wave solutions, Akhmediev breathers, Kuznetsov-Ma breathers, periodic solutions, and rogue wave solutions for this infinite-order hierarchy. We find that “even- order” equations in the set affect phase and “stretching factors” in the solutions, while “odd-order” equations affect the velocities. Hence odd-order equation solutions can be real functions, while even-order equation solutions are always complex
Frequency locking of modulated waves
We consider the behavior of a modulated wave solution to an
-equivariant autonomous system of differential equations under an
external forcing of modulated wave type. The modulation frequency of the
forcing is assumed to be close to the modulation frequency of the modulated
wave solution, while the wave frequency of the forcing is supposed to be far
from that of the modulated wave solution. We describe the domain in the
three-dimensional control parameter space (of frequencies and amplitude of the
forcing) where stable locking of the modulation frequencies of the forcing and
the modulated wave solution occurs.
Our system is a simplest case scenario for the behavior of self-pulsating
lasers under the influence of external periodically modulated optical signals
Modeling and simulations of beam stabilization in edge-emitting broad area semiconductor devices
A 2+1 dimensional PDE traveling wave model describing spatial-lateral
dynamics of edge-emitting broad area semiconductor devices is considered. A
numerical scheme based on a split-step Fourier method is presented and
implemented on a parallel compute cluster. Simulations of the model equations
are used for optimizing of existing devices with respect to the emitted beam
quality, as well as for creating and testing of novel device design concept
Nonlinear dynamics of semiconductor lasers with active optical feedback
An in-depth theoretical as well as experimental analysis of the nonlinear dynamics in semiconductor lasers with active optical feedback is presented. Use of a monolithically integrated multi-section device of sub-mm total length provides access to the short-cavity regime. By introducing an amplifier section as novel feature, phase and strength of the feedback can be separately tuned. In this way, the number of modes involved in the laser action can be adjusted. We predict and observe specific dynamical scenarios. Bifurcations mediate various transitions in the device output, from single-mode steady-state to self-pulsation and between different kinds of self-pulsations, reaching eventually chaotic behavior in the multi-mode limit
Mathematical models as research data via flexiformal theory graphs
Mathematical modeling and simulation (MMS) has now been established as an essential part
of the scientific work in many disciplines. It is common to categorize the involved
numerical data and to some extent the corresponding scientific software as research
data. But both have their origin in mathematical models, therefore any holistic approach
to research data in MMS should cover all three aspects: data, software, and
models. While the problems of classifying, archiving and making accessible are largely
solved for data and first frameworks and systems are emerging for software, the question
of how to deal with mathematical models is completely open.
In this paper we propose a solution -- to cover all aspects of mathematical models: the
underlying mathematical knowledge, the equations, boundary conditions, numeric
approximations, and documents in a flexi\-formal framework, which has enough structure to
support the various uses of models in scientific and technology workflows.
Concretely we propose to use the OMDoc/MMT framework to formalize mathematical models
and show the adequacy of this approach by modeling a simple, but non-trivial model: van
Roosbroeck's drift-diffusion model for one-dimensional devices. This formalization -- and
future extensions -- allows us to support the modeler by e.g. flexibly composing models,
visualizing Model Pathway Diagrams, and annotating model equations in documents as
induced from the formalized documents by flattening. This directly solves some of the
problems in treating MMS as "research data'' and opens the way towards more MKM
services for models
Demonstration of a self-pulsing photonic crystal Fano laser
Semiconductor lasers in use today rely on mirrors based on the reflection at
a cleaved facet or Bragg reflection from a periodic stack of layers. Here, we
demonstrate an ultra-small laser with a mirror based on the Fano resonance
between a continuum of waveguide modes and the discrete resonance of a
nanocavity. The Fano resonance leads to unique laser characteristics. Since the
Fano mirror is very narrow-band compared to conventional lasers, the laser is
single-mode and in particular, it can be modulated via the mirror. We show,
experimentally and theoretically, that nonlinearities in the mirror may even
promote the generation of a self-sustained train of pulses at gigahertz
frequencies, an effect that was previously only observed in macroscopic lasers.
Such a source is of interest for a number of applications within integrated
photonics
Physics and Applications of Laser Diode Chaos
An overview of chaos in laser diodes is provided which surveys experimental
achievements in the area and explains the theory behind the phenomenon. The
fundamental physics underpinning this behaviour and also the opportunities for
harnessing laser diode chaos for potential applications are discussed. The
availability and ease of operation of laser diodes, in a wide range of
configurations, make them a convenient test-bed for exploring basic aspects of
nonlinear and chaotic dynamics. It also makes them attractive for practical
tasks, such as chaos-based secure communications and random number generation.
Avenues for future research and development of chaotic laser diodes are also
identified.Comment: Published in Nature Photonic
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