92 research outputs found
The effect of nonlinear gain on the stability of evanescently coupled semiconductor laser arrays
We show that nonlinear gain saturation can enhance the stability of evanescently coupled semiconductor laser arrays.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71325/2/JAPIAU-73-1-459-1.pd
The Exact Correspondence between Phase Times and Dwell Times in a Symmetrical Quantum Tunneling Configuration
The general and explicit relation between the phase time and the dwell time
for quantum tunneling or scattering is investigated. Considering a symmetrical
collision of two identical wave packets with an one-dimensional barrier, here
we demonstrate that these two distinct transit time definitions give connected
results where, however, the phase time (group delay) accurately describes the
exact position of the scattered particles. The analytical difficulties that
arise when the stationary phase method is employed for obtaining phase
(traversal) times are all overcome. Multiple wave packet decomposition allows
us to recover the exact position of the reflected and transmitted waves in
terms of the phase time, which, in addition to the exact relation between the
phase time and the dwell time, leads to right interpretation for both of them.Comment: 11 pages, 2 figure
Spectral and picosecond temporal properties of flared guide Y‐coupled phase‐locked laser arrays
Spatio‐spectral and spatio‐temporal properties of flared waveguide ‘‘Y’’‐coupled laser arrays are investigated in both cw and pulsed operation. In each case, regular sustained self‐pulsations are exhibited. Destabilization of phase locking, caused by amplitude phase coupling, is thought to be the origin of the pulsations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70525/2/APPLAB-53-24-2380-1.pd
Elevated temperature material behaviour of high strength steel
The support provided by the Engineering and Physical Sciences Research Council (EPSRC) and TWI Ltd for the work described in this paper is gratefully acknowledged
Behaviour of high strength steel columns under fire conditions
Engineering and Physical Sciences Research Council and TWI lt
Resonant laser tunnelling
We propose an experiment involving a gaussian laser tunneling through a twin
barrier dielectric structure. Of particular interest are the conditions upon
the incident angle for resonance to occur. We provide some numerical
calculations for a particular choice of laser wave length and dielectric
refractive index which confirm our expectations.Comment: 15 pages, 6 figure
Simultaneous optical pulse compression and wing reduction
We report the compression of picosecond optical pulses with a simultaneous reduction of the pulse wings by using a combination of both the self-phase modulation and nonlinear birefringence effects in a modified optical-fiber pulse compressor.Peer reviewedElectrical and Computer Engineerin
Locking bandwidth of two laterally coupled semiconductor lasers subject to optical injection
We report here for the first time (to our knowledge), a new and universal mechanism by which a two-element laser array is locked to external optical injection and admits stably injection-locked states within a nontrivial trapezoidal region. The rate equations for the system are studied both analytically and numerically. We derive a simple mathematical expression for the locking conditions, which reveals that two parallel saddle-node bifurcation branches, not reported for conventional single lasers subject to optical injection, delimit the injection locking range and its width. Important parameters are the linewidth enhancement factor, the laser separation, and the frequency offset between the two laterally-coupled lasers; the influence of these parameters on locking conditions is explored comprehensively. Our analytic approximations are validated numerically by using a path continuation technique as well as direct numerical integration of the rate equations. More importantly, our results are not restricted by waveguiding structures and uncover a generic locking behavior in the lateral arrays in the presence of injection
General Stability Analysis of Synchronized Dynamics in Coupled Systems
We consider the stability of synchronized states (including equilibrium
point, periodic orbit or chaotic attractor) in arbitrarily coupled dynamical
systems (maps or ordinary differential equations). We develop a general
approach, based on the master stability function and Gershgorin disc theory, to
yield constraints on the coupling strengths to ensure the stability of
synchronized dynamics. Systems with specific coupling schemes are used as
examples to illustrate our general method.Comment: 8 pages, 1 figur
Nonlinear localized waves in a periodic medium
We analyze the existence and stability of nonlinear localized waves in a
periodic medium described by the Kronig-Penney model with a nonlinear defect.
We demonstrate the existence of a novel type of stable nonlinear band-gap
localized states, and also reveal an important physical mechanism of the
oscillatory wave instabilities associated with the band-gap resonances.Comment: 4 pages, 5 figure
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