Excitability in optical systems close to -symmetry

Abstract

We report theoretically and experimentally on excitability in semiconductor ring lasers in order to reveal a mechanism of excitability, general for systems close to Z 2 -symmetry. The global shapes of the invariant manifolds of a saddle in the vicinity of a homoclinic loop determine the origin of excitability and the features of the excitable pulses. We show how to experimentally make a semiconductor ring laser excitable by breaking the Z 2 -symmetry in a controlled way. The experiments confirm the theoretical predictions.

Noise-induced escape in an excitable system

“…Nonbiological systems, e.g., lasers and semiconductors [3][4][5][6][7], also display excitable behavior, and it has come to be appreciated that excitable systems can usefully be considered as forming a distinct class characterized by their own particular modes of behavior.…”

“…The latter noise has attracted less attention, even though it appears explicitly in the archetypical Hodgkin-Huxley model [15,16] and there is evidence that it plays an important role in neural regulatory networks [17]. Note that, in excitable lasers [5,7], noise is present in both the fast and slow variables.…”

Excitability in optically injected microdisk lasers with phase controlled excitatory and inhibitory response

“…An approach more amenable to integration is proposed in [12], in which an RF connection between a photodetector and a hybrid laser allows for both inhibitory and excitatory inputs. A fully integrated all-optical alternative is demonstrated both numerically and experimentally for Semiconductor Ring Lasers (SRLs) by Gelens, Coomans et al [13][14][15][16]. SRLs support two counterpropagating modes, which are both linearly and non-linearly coupled to each other by intermodal coupling and cross-gain saturation, respectively.…”

“…If the laser is operated in the unidirectional regime with two stable states, near the onset of this AO regime, theoretically, excitability is expected, but as a drawback of the symmetry of the system, the attraction basins of both stable states are equal in size and, consequently, there will be a competition between mode-hopping events between both stable states and excitable excursions [13]. This drawback can be solved by inducing an asymmetry in the intermodal coupling [14][15][16]. This causes the basin of one of these equilibria to shrink drastically, making the state metastable.…”

Excitation transfer between optically injected microdisk lasers

“…Theoretically, they outperform the computational power of non-spiking artificial neural network types [1]. Given the natural appearance of excitability in many different non-linear optical components, both lasing [2,3,4,5,6,7] and non-lasing [8,9,10], there is an intrinsic advantage of implementing such networks in photonic hardware as this would allow to operate at time-scales that are orders of magnitude faster than typical biological and electronic implementations [11]. In this article, microdisk lasers are being proposed as a basic building block for an integrated photonic SNN platform.…”