Quantitative identification of dynamical transitions in a semiconductor laser with optical feedback

Abstract

Identifying transitions to complex dynamical regimes is a fundamental open problem with many practical applications. Semi- conductor lasers with optical feedback are excellent testbeds for studying such transitions, as they can generate a rich variety of output signals. Here we apply three analysis tools to quantify various aspects of the dynamical transitions that occur as the laser pump current increases. These tools allow to quantitatively detect the onset of two different regimes, low-frequency fluctuations and coherence collapse, and can be used for identifying the operating conditions that result in specific dynamical properties of the laser output. These tools can also be valuable for analyzing regime transitions in other complex systems.

Comparing the dynamics of periodically forced lasers and neurons

“…For D=3, we have 3!=6 possible OPs: 012 (ΔT 3 >ΔT 2 >ΔT 1 ), 021 (ΔT 2 >ΔT 3 >ΔT 1 ), 102 (ΔT 3 >ΔT 1 >ΔT 2 ), 120 (ΔT 2 >ΔT 1 > ΔT 3 ), 201 (ΔT 1 >ΔT 3 >ΔT 2 ) and 210 (ΔT 1 >ΔT 2 >ΔT 3 ). As in previous works [38,55,56,62,63] we use D=3, which allows identifying temporal relations among four consecutive spikes. As the number of possible patterns increases as D!, a larger D significantly increases the data requirements, because very long sequences of spikes are needed for a robust estimation of the probabilities of the D!…”

“…We also compare the laser spikes with the neuronal spikes using OP analysis [38,40]. This is a popular technique to investigate complex signals, which has been extensively used to characterize the dynamical regimes of semiconductor lasers with optical feedback [41,[48][49][50][51][52][53][54][55][56][57]. A main advantage of this methodology is that, in its simplest implementation, it has only one parameter that is the size, D of the pattern, which determines the length of the temporal correlations studied: the D!…”

Experimental characterization of the transition to coherence collapse in a semiconductor laser with optical feedback

“…4 we analyze the variation of σ with the laser current, for various feedback strengths. In [21] the current value for which σ is maximum (indicated with a dot) was identified as the onset of the LFF-CC transition. We note that, for strong feedback, the LFF-CC transition moves to higher pump currents as the feedback increases; in contrast, for weak feedback (OD between 0.6 and 1.2) the pump current at which the LFF-CC transition occurs remains nearly constant as the feedback increases.…”

“…The experimental setup is as in Ref. [21]. A 685 nm semiconductor laser (AlGaInP multi-quantum well HL6750MG), with solitary threshold current I th,sol = 26.74 mA has part of its output intensity fed back to the laser cavity by a mirror.…”

“…}, between consecutive intensity dropouts (interdropout intervals, IDIs). To define the timing of the dropouts two thresholds are used [21]: t i is defined as the time when the intensity falls below a predefined detection threshold; then, the intensity has to grow above a second threshold, I i = 0, before the next dropout can be detected. This second threshold is needed in order to avoid detecting as dropouts the fluctuations that occur during the recovery process.…”