58 research outputs found
Coherence and anticoherence resonance in high-concentration erbium-doped fiber laser
We report an experimental study of low-frequency (~10 kHz) self-pulsing of the output intensity in a high- concentration erbium-doped fiber laser. We suggest that the fast intensity fluctuations caused by multimode and polarization instabilities play the role of an external noise source, leading to low-frequency auto-oscillations through a coherence resonance scenario
Experimental realization of a highly secure chaos communication under strong channel noise
A one-way coupled spatiotemporally chaotic map lattice is used to contruct
cryptosystem. With the combinatorial applications of both chaotic computations
and conventional algebraic operations, our system has optimal cryptographic
properties much better than the separative applications of known chaotic and
conventional methods. We have realized experiments to pratice duplex voice
secure communications in realistic Wired Public Switched Telephone Network by
applying our chaotic system and the system of Advanced Encryption Standard
(AES), respectively, for cryptography. Our system can work stably against
strong channel noise when AES fails to work.Comment: 15 pages, 5 figure
Chaos in a generalized Lorenz system
A three-component dynamic system with influence of pumping and nonlinear
dissipation describing a quantum cavity electrodynamic device is studied.
Different dynamical regimes are investigated in terms of divergent trajectories
approaches and fractal statistics. It has been shown, that in such a system
stable and unstable dissipative structures type of limit cycles can be formed
with variation of pumping and nonlinear dissipation rate. Transitions to
chaotic regime and the corresponding chaotic attractor are studied in details
Detecting local synchronization in coupled chaotic systems
We introduce a technique to detect and quantify local functional dependencies
between coupled chaotic systems. The method estimates the fraction of locally
syncronized configurations, in a pair of signals with an arbitrary state of
global syncronization. Application to a pair of interacting Rossler oscillators
shows that our method is capable to quantify the number of dynamical
configurations where a local prediction task is possible, also in absence of
global synchronization features
Spiral attractor created by vector solitons
Mode-locked lasers emitting a train of femtosecond pulses called dissipative solitons are an enabling technology for metrology, high-resolution spectroscopy, fibre optic communications, nano-optics and many other fields of science and applications. Recently, the vector nature of dissipative solitons has been exploited to demonstrate mode locked lasing with both locked and rapidly evolving states of polarisation. Here, for an erbium-doped fibre laser mode locked with carbon nanotubes, we demonstrate the first experimental and theoretical evidence of a new class of slowly evolving vector solitons characterized by a double-scroll chaotic polarisation attractor substantially different from Lorenz, Rössler and Ikeda strange attractors. The underlying physics comprises a long time scale coherent coupling of two polarisation modes. The observed phenomena, apart from the fundamental interest, provide a base for advances in secure communications, trapping and manipulation of atoms and nanoparticles, control of magnetisation in data storage devices and many other areas
Polarisation dynamics of vector soliton molecules in mode locked fibre laser
Two fundamental laser physics phenomena - dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning
Performance characteristics of positive and negative delayed feedback on chaotic dynamics of directly modulated InGaAsP semiconductor lasers
The chaotic dynamics of directly modulated semiconductor lasers with delayed
optoelectronic feedback is studied numerically. The effects of positive and
negative delayed optoelectronic feedback in producing chaotic outputs from such
lasers with nonlinear gain reduction in its optimum value range is investigated
using bifurcation diagrams. The results are confirmed by calculating the
Lyapunov exponents. A negative delayed optoelectronic feedback configuration is
found to be more effective in inducing chaotic dynamics to such systems with
nonlinear gain reduction factor in the practical value range.Comment: 18 pages, 16 figures. To appear In Pramana - journal of physic
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