2,482 research outputs found
Multi-stabilities and symmetry-broken one-colour and two-colour states in closely coupled single-mode lasers
We theoretically investigate the dynamics of two mutually coupled identical
single-mode semi-conductor lasers. For small separation and large coupling
between the lasers, symmetry-broken one-colour states are shown to be stable.
In this case the light output of the lasers have significantly different
intensities while at the same time the lasers are locked to a single common
frequency. For intermediate coupling we observe stable symmetry-broken
two-colour states, where both lasers lase simultaneously at two optical
frequencies which are separated by up to 150~GHz. Using a five dimensional
model we identify the bifurcation structure which is responsible for the
appearance of symmetric and symmetry-broken one-colour and two-colour states.
Several of these states give rise to multi-stabilities and therefore allow for
the design of all-optical memory elements on the basis of two coupled
single-mode lasers. The switching performance of selected designs of optical
memory elements is studied numerically.Comment: 12 pages, 15 figure
Dispersion-induced dynamics of coupled modes in a semiconductor laser with saturable absorption
We present an experimental and theoretical study of modal nonlinear dynamics
in a specially designed dual-mode semiconductor Fabry-Perot laser with a
saturable absorber. At zero bias applied to the absorber section, we have found
that with increasing device current, single mode self-pulsations evolve into a
complex dynamical state where the total intensity experiences regular bursts of
pulsations on a constant background. Spectrally resolved measurements reveal
that in this state the individual modes of the device can follow highly
symmetric but oppositely directed spiralling orbits. Using a generalization of
the rate equation description of a semiconductor laser with saturable
absorption to the multimode case, we show that these orbits appear as a
consequence of the interplay between the material dispersion in the gain and
absorber sections of the laser. Our results provide insights into the factors
that determine the stability of multimode states in these systems, and they can
inform the development of semiconductor mode-locked lasers with tailored
spectra.Comment: 10 pages, 10 figure
Asymptotics of a small liquid drop on a cone and plate rheometer
A cone and a plate rheometer is a laboratory apparatus used to measure the viscosity and other related parameters of a non-Newtonian liquid subject to an applied force. A small drop, of order millimetres, of the liquid is located between the horizontal plate and the shallow cone of the rheometer. Rotation of the cone ensues, the liquid begins to flow and the plate starts to rotate. Liquid parameters are inferred based on the difference in the applied rotational force and the resulting rotational force of the plate. To describe the flow of the drop, the initial drop configuration, before rotation commences, must be determined. The equilibrium drop profile is given by the solution to the well-known nonlinear Young-Laplace equation. We formulate asymptotic solutions for the drop profile based on the small Bond number. The modelling of the drop exhibits a rich asymptotic structure consisting of five distinct scalings which are resolved via the method matched asymptotics
The Platypus Genome Unraveled
The genome of the platypus has been sequenced, assembled, and annotated by an international genomics team. Like the animal itself the platypus genome contains an amalgam of mammal, reptile, and bird-like features
Military base redevelopment : issues facing private developers
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1997.Includes bibliographical references (leaves 73-75).by Stephen T. O'Brien.M.S
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