Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser

We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters. © 2011 Author(s)

Marshall University Department of Music presents Art and Music

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Stability Analysis of Quantum-Dot Spin-VCSELs

Spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) and vertical external-cavity surface-emitting lasers (spin-VECSELs) are of interest since their output polarization can be manipulated by spin-selective pumping, either optical or electrical. These devices, using quantum dot (QD) material for the active region, have shown instability (periodic oscillations) and polarization switching in previous theoretical simulations based on a rate equation model. It has been recognized that the polarization switching occurs between two possible sets of solutions, termed here in-phase and out-of-phase. The present contribution seeks to give enhanced understanding of these behaviors by applying a stability analysis to the system of equations used for such simulations. The results indicate that the choice of in-phase and out-of-phase solutions that appear in a time-dependent simulation is determined by the condition that the corresponding steady-state solutions are stable against small perturbations. The stability analysis is shown to be a valuable theoretical tool for future study of spin-V(E)SELs in the context of understanding and guiding future experimental research

Polarization and time-resolved dynamics of a 1550-nm VCSEL subject to orthogonally polarized optical injection

We report a first experimental study of the simultaneous temporal and polarization-resolved dynamics of a 1550-nm vertical-cavity surface-emitting laser (VCSEL) subject to orthogonally polarized optical injection. A novel technique is used to reveal the behavior of both polarizations at the VCSEL's output. In general, the same type of dynamics can be seen in both polarizations of the fundamental transverse mode but with unequal intensity/modulation depth. We show that both polarizations exhibit period one and chaotic dynamics and reveal antiphase dynamics. These results offer promise for the development of dual-channel, anticorrelated periodic and chaotic-signal generators with a single VCSEL for use as oscillators or chaotic sources in present and future optical networks

Algebraic expressions for the polarisation response of spin-VCSELs

Closed-form expressions are derived for the relationship between the polarisation of the output and that of the pump for spin-polarised vertical-cavity surface-emitting lasers. These expressions are based on the spin-flip model (SFM) combined with the condition that the carrier recombination time is much greater than both the spin relaxation time and the photon lifetime. Allowance is also included for misalignment between the principal axes of birefringence and dichroism. These expressions yield results that are in excellent agreement both with previously published numerical calculations and with further tests for a wide range of parameters. Trends with key parameters of the SFM are easily deduced from these expression

Stability Boundaries in Laterally-Coupled Pairs of Semiconductor Lasers

The dynamic behaviour of coupled pairs of semiconductor lasers is studied using normal-mode theory, applied to one-dimensional (slab) and two-dimensional (circular cylindrical) real index confined structures. It is shown that regions of stable behaviour depend not only on pumping rate and laser separation, but also on the degree of guidance in the structures. Comparison of results between normal-mode and coupled-mode theories for these structures leads to the tentative conclusion that the accuracy of the latter is determined by the strength of self-overlap and cross-overlap of the symmetric and antisymmetric normal modes in the two lasers

Dynamics of laterally-coupled pairs of spin-VCSELs

A newly-developed normal mode model of laser dynamics in a generalised array of waveguides is applied to extend the spin-flip model (SFM) to pairs of evanescently-coupled spin-VCSELS. The effect of high birefringence is explored, revealing new dynamics and regions of bistability. It is shown that optical switching of the polarisation states of the lasers may be controlled through the optical pump and that, under certain conditions, the polarisation of one laser may be switched by controlling the intensity and polarisation in the other

Optical neuron using polarisation switching in a 1550nm-VCSEL

We report a new approach to mimic basic functionalities of a neuron using a 1550 nm Vertical Cavity Surface Emitting Laser (VCSEL) which is based on the polarisation switching (PS) that can be induced in these devices when subject to polarised optical injection. Positive and negative all-optical threshold operations are demonstrated experimentally using external optical injection into the two orthogonal polarizations of the fundamental transverse mode. The polarisation of the light emitted by the device is used to determine the state of the VCSEL-Neuron, active (orthogonal) or inactive (parallel). This approach forms a new way to reproduce optically the response of a neuron to an excitatory and an inhibitory stimulus. © 2010 Optical Society of America

The culturable intestinal microbiota of triploid and diploid juvenile Atlantic salmon (Salmo salar) - a comparison of composition and drug resistance

<p>Abstract</p> <p>Background</p> <p>With the increased use of ploidy manipulation in aquaculture and fisheries management this investigation aimed to determine whether triploidy influences culturable intestinal microbiota composition and bacterial drug resistance in Atlantic salmon (<it>Salmo salar</it>). The results could provide answers to some of the physiological differences observed between triploid and diploid fish, especially in terms of fish health.</p> <p>Results</p> <p>No ploidy effect was observed in the bacterial species isolated, however, triploids were found to contain a significant increase in total gut microbiota levels, with increases in <it>Pseudomonas </it>spp., <it>Pectobacterium carotovorum</it>, <it>Psychrobacter </it>spp., <it>Bacillus </it>spp., and <it>Vibrio </it>spp., (12, 42, 9, 10, and 11% more bacteria in triploids than diploids, respectively), whereas a decrease in <it>Carnobacterium </it>spp., within triploids compared to diploids was close to significant (8% more bacteria in diploids). With the exception of gentamicin, where no bacterial resistance was observed, bacterial isolates originating from triploid hosts displayed increased resistance to antibacterials, three of which were significant (tetracycline, trimethoprim, and sulphonamide).</p> <p>Conclusion</p> <p>Results indicate that triploidy influences both the community and drug resistance of culturable intestinal microbiota in juvenile salmon. These results demonstrate differences that are likely to contribute to the health of triploid fish and have important ramifications on the use of antibacterial drugs within aquaculture.</p

Tunable microwave signal generator with an optically-injected 1310nm QD-DFB laser

Tunable microwave signal generation with frequencies ranging from below 1 GHz to values over 40 GHz is demonstrated experimentally with a 1310nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Microwave signal generation is achieved using the period 1 dynamics induced in the QD DFB under optical injection. Continuous tuning in the positive detuning frequency range of the quantum dot's unique stability map is demonstrated. The simplicity of the experimental configuration offers promise for novel uses of these nanostructure lasers in Radio-over-Fiber (RoF) applications and future mobile networks. © 2013 Optical Society of America