Comparison of models of fast saturable absorption in passively modelocked lasers

Abstract

Fast saturable absorbers (FSAs) play a critical role in stabilizing many passively modelocked lasers. The most commonly used averaged model to study these lasers is the Haus modelocking equation (HME) that includes a third-order nonlinear FSA. However, it predicts a narrow region of stability that is inconsistent with experiments. To better replicate the laser physics, averaged laser models that include FSAs with higher-than-third-order nonlinearities have been introduced. Here, we compare three common FSA models to each other and to the HME using the recently-developed boundary tracking algorithms. The three FSA models are the cubic-quintic model, the sinusoidal model, and the algebraic model. We find that all three models predict the existence of a stable high-energy solution that is not present in the HME and have a much larger stable operating region. We also find that all three models predict qualitatively similar stability diagrams. We conclude that averaged laser models that include FSAs with higher-than-third-order nonlinearity should be used when studying the stability of passively modelocked lasers.

Impact of Spectral Filtering on Multipulsing Instability in Mode-Locked Fiber Lasers

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Internal nonlinear transmission in an Yb mode-locked fiber laser through bifurcations

“…Many numerical models have been proposed to describe the dynamics of MLFL. However, accurate quantitative comparison between experiments and theory is difficult to achieve, due to the complexity of the physical system and the large number of parameters affecting the resulting dynamics [19,20]. Any of those models could be used to show that dynamical systems undergoing bifurcation display sudden variations in the average value of the dynamical variables [21].…”

Thermal instabilities, frequency comb formation, and temporal oscillations in Kerr microresonators

“…This method, which combines efficient computational tools with ideas from dynamical systems theory, allows for a comprehensive mapping of stable solutions of nonlinear evolution equations for large sets of parameter values. In previous works we applied this method to models of mode-locked lasers [17,[30][31][32][33] and pumped Kerr resonators [18,19], where we studied the existence and stability of dissipative cnoidal waves. Cnoidal waves are spatially periodic waveforms that can arise as Turing patterns by modulational instability of continuous-wave light for blue-and moderately red-detuned pumping, but become a periodic train of wellseparated pulses in the highly red-detuned pump regime, where stable cnoidal waves coexist with stable single cavity solitons.…”