Axel Dolcemascolo

Excitability is a property that is shared by many different systems, from biology to chemistry to laser systems. It is defined as the possibility to respond to an external perturbation by either producing an excitable response (e.g. a spike) if the perturbation is over a certain threshold, or otherwise relaxing to its stable state. The feasibility of producing an excitable event using a laser with injected signal was already suggested several years ago [1], where the phase dynamics of these events can be basically described by the Adler equation. An observation of such events was realized in [2], while a control of their generation was obtained in [3].

Our work is also focused on the generation of excitable pulses using a laser system with optical injection, where the perturbation used to generate the excitable events consists of two narrow pulses of a duration of 0.12 ns, separated by a variable time-delay, from a minimum of 0.08 ns to a maximum of 1.05 ns. What we unexpectedly find is that there is a particular delay, around 0.10 ns, where there is a higher efficiency of generating a single response. This means that the system has a preferred frequency to which it will respond: this is called a resonator property. We also observed multipulse excitability, that is, the possibility of producing two or more responses for a single perturbation. Both of these properties cannot be explained by the simple Adler model.

Similar features of resonator property, multipulse excitability and refractory period [4] can already be found in the case of neurons, which are the most typical example of excitable system. Guided by this observation we started to investigate the connections between these two words, the laser word and the neuroscience word. Using tools from Singolar Pertubation theory we study the theoretical model of a class B laser, and we try to describe the behavior of our system going beyond the Adler equation. We also investigate the connections between our system and the dynamics of neuronal models that better fit our physical data. The long term goal we have in mind is to exploit the neuron-like properties of our system for optical data processing and to provide possible insight about complex solitons interactions in forced oscillatory media [5].

1. Coullet, P., D. Daboussy, and J. R. Tredicce. “Optical Excitable Waves”. Physical Review E 58, no. 5 (1998)

2. Goulding, D., S. P. Hegarty, O. Rasskazov, S. Melnik, M. Hartnett, G. Greene, J. G. McInerney, D. Rachinskii, and G. Huyet. “Excitability in a Quantum Dot Semiconductor Laser with Optical Injection”, Physical Review Letters 98, no. 15 (2007)

3. Turconi, M., B. Garbin, M. Feyereisen, M. Giudici, and S. Barland. “Control of Excitable Pulses in an Injection-Locked Semiconductor Laser”, Physical Review E 88, no. 2 (2013)

4. Garbin, B., A. Dolcemascolo, F. Prati, J. Javaloyes, G. Tissoni, and S. Barland. “Refractory Period of an Excitable Semiconductor Laser with Optical Injection”, Physical Review E 95, no. 1 (2017)

5. Garbin, Bruno, Julien Javaloyes, Giovanna Tissoni, and Stephane Barland. “Topological Solitons as Addressable Phase Bits in a Driven Laser”, Nature Communications 6 (2015)