Lévy Statistics and Glassy Behavior of Light in Random Fiber Lasers

Abstract

Abstract:The interest in random fiber lasers (RFLs), first demonstrated one decade ago, is still growing and their basic characteristics have been studied by several authors. RFLs are open systems that present instabilities in the intensity fluctuations due to the energy exchange among their non-orthogonal quasi-modes. In this work, we present a review of the recent investigations on the output characteristics of a continuous-wave erbium-doped RFL, with emphasis on the statistical behavior of the emitted intensity fluctuations. A progression from the Gaussian to Lévy and back to the Gaussian statistical regime was observed by increasing the excitation laser power from below to above the RFL threshold. By analyzing the RFL output intensity fluctuations, the probability density function of emission intensities was determined, and its correspondence with the experimental results was identified, enabling a clear demonstration of the analogy between the RFL phenomenon and the spin-glass phase transition. A replica-symmetry-breaking phase above the RFL threshold was characterized and the glassy behavior of the emitted light was established. We also discuss perspectives for future investigations on RFL systems.

Influence of the Excitation Light Disorder on the Spatial Coherence in the Stimulated Raman Scattering and Random Lasing Coupled Regime

“…Due to the interesting characteristics that RLs present for the investigation of new optical phenomena and applications, various studies have been carried out to find new materials or mechanisms that optimize their performance and efficiency. − Actually, the most used strategy consists of managing the scattering strength, for example, from the variation in the scattering particle density, or the excitation volume of the RL medium. This experimental procedure can also be used to tune the spatial coherence of RLs. , In a different approach, we recently demonstrated that by introducing a degree of randomness on the intensity distribution of the spatial light pattern that pumps a random lasing medium, it is possible to control and improve the RL efficiency by more than 1 order of magnitude .…”

Influence of the Fifth-Order Nonlinearity of Gold Nanorods on the Performance of Random Lasers

“…The first three terms on the right describe the linear, quadratic, and cubic effective nonlinearities, respectively. For instance, phenomena such as second-harmonic generation and sum-frequency generation associated with were reported in RL experiments, due to self-induced second-order wave-mixing processes. , Moreover, variations in frequency and spatial localization of lasing modes, as well as laser intensity fluctuations, are attributed to the intensity-dependent refractive index associated with the third-order nonlinearity. , The third-order nonlinearity, associated with , also plays an important role in coupling the RL optical modes in a process leading to the replica symmetry-breaking phenomenon. − …”