We revisit the laser model with cavity loss modulation, from which evidence of chaos and generalized multistability was discovered in 1982. Multistability refers to the coexistence of two or more attractors in nonlinear dynamical systems. Despite its relative simplicity, the adopted model shows us how the multistability depends on the dissipation of the system. The model is then tested under the action of a secondary sinusoidal perturbation, which can remove bistability when a suitable relative phase is chosen. The surviving attractor is the one with less dissipation. This control strategy is particularly useful when one of the competing attractors is a chaotic attractor.

The near-threshold behavior of a single-mode ${\mathrm{CO}}_2$ laser has been investigated by applying a linear modulation to the excitation current. The associated delayed bifurcation has been characterized in terms of first-passage-time distributions for different sweep rates. A theoretical model provides good agreement with the experimental data. In particular, we are able to assign the initial photon number below threshold.

Detection of chaos in experimental data is a crucial issue in nonlinear science. Historically, one of the first evidences of a chaotic behavior in experimental recordings came from laser physics. In a recent work, a Minimal Universal Model of chaos was developed by revisiting the model of laser with feedback, and a first electronic implementation was discussed. Here, we propose an upgraded electronic implementation of the Minimal Universal Model, which allows for a precise and reproducible analysis of the model’s parameters space. As a marker of a possible chaotic behavior the variability of the spiking activity that characterizes one of the system’s coordinates was used. Relying on a numerical characterization of the relationship between spiking activity and maximum Lyapunov exponent at different parameter combinations, several potentially chaotic settings were selected. The analysis via divergence exponent method of experimental time series acquired by using those settings confirmed a robust chaotic behavior and provided values of the maximum Lyapunov exponent that are in very good agreement with the theoretical predictions. The results of this work further uphold the reliability of the Minimal Universal Model. In addition, the upgraded electronic implementation provides an easily controllable setup that allows for further developments aiming at coupling multiple chaotic systems and investigating synchronization processes.

The exploration of chaos, synchronization, and circuit implementation in analog simulations unveils a versatile framework with diverse applications. Originating from a universal chaos model rooted in laser physics, its adaptability extends to neural dynamics and random number generation, where both rely on characteristic time scales. Circuit implementations using op-amps and analog multipliers offer tangible avenues for exploration. However, challenges like bias and trajectory distortion drive the need for innovative solutions. Through numerical integration and circuit simulations, analysis of chaotic regimes such as Sub-harmonic Chaos (SC) and Homoclinic Chaos (HC) reveals crucial behaviors for applications like secure communications. Despite experimental hurdles, advancements in circuit design promise novel pathways for chaos synchronization studies. Understanding the intricate interplay between chaos and these systems is vital, given their reliance on characteristic time scales. Additionally, exploring chaos synchronization, especially within analog circuits, shows potential for revolutionizing information processing capabilities, despite inherent challenges. Progress in circuit design persists, forging new avenues in chaos synchronization studies, shaping a dynamic landscape poised for further exploration and innovation.

We present an experimental investigation of the complex dynamics of a modulated relaxation oscillator implemented by using a unipolar junction transistor (UJT) showing the transition to chaos through torus breakdown. In a previous paper a continuous model was introduced for the same system, explaining chaos based on analogy with a memristor. We propose here a new approach based on a piecewise linear model with delay considering a measured parasitic delay effect. The inclusion of this delay, accounting for memory effects, increases the dimensionality of the model, allowing the transition to chaos as observed in the experiment. The piecewise delayed model shows analogies with a two-dimensional leaky integrate-and-fire model used in neurodynamics.