115 research outputs found
Exploring multi-stability in semiconductor ring lasers: theory and experiment
We report the first experimental observation of multi-stable states in a
single-longitudinal mode semiconductor ring laser. We show how the operation of
the device can be steered to either monostable, bistable or multi-stable
dynamical regimes in a controlled way. We observe that the dynamical regimes
are organized in well reproducible sequences that match the bifurcation
diagrams of a two-dimensional model. By analyzing the phase space in this
model, we predict how the stochastic transitions between multi-stable states
take place and confirm it experimentally.Comment: 4 pages, 5 figure
Excitability in semiconductor microring lasers: Experimental and theoretical pulse characterization
We characterize the operation of semiconductor microring lasers in an
excitable regime. Our experiments reveal a statistical distribution of the
characteristics of noise-triggered optical pulses that is not observed in other
excitable systems. In particular, an inverse correlation exists between the
pulse amplitude and duration. Numerical simulations and an interpretation in an
asymptotic phase space confirm and explain these experimentally observed pulse
characteristics.Comment: 9 pages, 10 figure
Topological insight into the non-Arrhenius mode hopping of semiconductor ring lasers
We investigate both theoretically and experimentally the stochastic switching
between two counter-propagating lasing modes of a semiconductor ring laser.
Experimentally, the residence time distribution cannot be described by a simple
one parameter Arrhenius exponential law and reveals the presence of two
different mode-hop scenarios with distinct time scales. In order to elucidate
the origin of these two time scales, we propose a topological approach based on
a two-dimensional dynamical system.Comment: 4 pages, 3 figure
Integrated photonic delay-lasers for reservoir computing
Currently, multiple photonic reservoir computing systems show great promise for providing a practical yet powerful hardware substrate for neuromorphic computing. Among those, delay-based systems offer a simple technological route to implement photonic neuromorphic computation. Its operation boils down to a time-multiplexing with the delay length limiting the processing speed. As most optical setups end up to be bulky employing long fiber loops or free-space optics, the processing speeds are ranging from kSa/s to tens of MSa/s. Therefore, we focus on external cavities which are far shorter than what has been realized before in such experiments. We present experimental results of reservoir computing based on a semiconductor laser, operating in a single mode regime around 1550nm, with a 10.8cm delay line. Both are integrated on an active/passive InP photonic chip built on the Jeppix platform. Using 23 virtual nodes spaced 50 ps apart in the integrated delay section, we increase the processing speed to 0.87GSa/s. The computational performance is benchmarked on a forecasting task applied to chaotic time samples. Competitive performance is observed for injection currents above threshold, with higher pumps having lower prediction errors. The feedback strength can be controlled by electrically pumping integrated amplifiers within the delay section. Nevertheless, we find good performance even when these amplifiers are unpumped. To proof the relevance and necessity of the external cavity on the computational capacity, we have analysed linear and nonlinear memory tasks. We also propose several post-processing methods, which increase the performance without a penalty to speed
Thermodynamic Field Theory with the Iso-Entropic Formalism
A new formulation of the thermodynamic field theory (TFT) is presented. In
this new version, one of the basic restriction in the old theory, namely a
closed-form solution for the thermodynamic field strength, has been removed. In
addition, the general covariance principle is replaced by Prigogine's
thermodynamic covariance principle (TCP). The introduction of TCP required the
application of an appropriate mathematical formalism, which has been referred
to as the iso-entropic formalism. The validity of the Glansdorff-Prigogine
Universal Criterion of Evolution, via geometrical arguments, is proven. A new
set of thermodynamic field equations, able to determine the nonlinear
corrections to the linear ("Onsager") transport coefficients, is also derived.
The geometry of the thermodynamic space is non-Riemannian tending to be
Riemannian for hight values of the entropy production. In this limit, we obtain
again the same thermodynamic field equations found by the old theory.
Applications of the theory, such as transport in magnetically confined plasmas,
materials submitted to temperature and electric potential gradients or to
unimolecular triangular chemical reactions can be found at references cited
herein.Comment: 35 page
Polarization stabilization in vertical-cavity surface-emitting lasers through asymmetric current injection
We present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting lasers (VCSELs) stabilizes the polarization of the emitted light. Anisotropies in the gain and loss mechanisms introduced by asymmetric current injection are considered to explain this effect. The design scheme opens perspectives to obtain actual polarization control in VCSEL
- …