Multiple noise-like pulsing of a figure-eight fibre laser

Abstract

In this work we study multiple noise-like pulse generation in a 320 m long passively mode-locked erbium-doped figure-eight fibre laser in the normal net dispersion regime. The nonlinear optical loop mirror (NOLM) that is used as a mode locker operates through polarization asymmetry, which allows us to control its switching power by birefringence adjustments at the NOLM input, using a half-wave retarder (HWR). Over some range of the HWR orientation, a single noise-like pulse is observed in the cavity. Its peak power is adjustable as it remains clamped to the variable switching power, and its duration varies inversely between ∼5 and ∼22 ps. Beyond the HWR position, corresponding to the longest duration, the pulse splits into several noise-like pulses. These multiple pulses usually present a walkoff, however they can be synchronized through slight birefringence adjustments, although they are not evenly spaced in time. Up to 12 simultaneous noise-like pulses were observed experimentally, with a duration of ∼2 ns. Multiple pulsing and synchronization of the pulses are interpreted in terms of mechanisms of interaction between pulses. Multiple pulsing appears to be indirectly related to the peak power limiting effect of the NOLM.

Numerical study of multiple noise-like pulsing in a dispersion-managed figure-eight fibre laser

“…This contrasts with the common behaviour of lasers in single-NLP operation, where the NLP duration and energy grow proportionally to pump power [16,25]. On the other hand, this result is consistent with the experimental observation of nearly quantized 'units' in complex NLPs in dispersion-managed cavities, each having roughly the same duration and energy [14,20,21,26]. Now we focus our attention on the effect of varying the dispersion parameters.…”

“…In previous publications, we studied experimentally NLP generation using a ~200 m-long figure-eight fibre laser (F8L) including a polarization-imbalanced nonlinear optical loop mirror (NOLM) and presenting a strong dispersion map [14,20,21,26]. Although for some settings a single, compact NLP with rectangular envelope was circulating in the cavity, in other cases the NLP displayed a kind of composite, 'comblike' temporal envelope, in which a series of similar, equidistant sub-units with sub-ns temporal duration were packed together [14,20]. Through slight wave retarder adjustments, the cohesion between some of these sub-packets could be broken, leading to the liberation of some sub-units, which then initiated complex drifting dynamics [21,26].…”

1.3 µm dissipative soliton resonance generation in Bismuth doped fiber laser

“…The difference between them is that the DSR pulse is a single pulse, whereas the NLP is a wave packet consisting of many sub-pulses in sub-picoseconds with varying width and peak intensities. Thus, the autocorrelation (AC) trace of an NLP usually shows a sub-picosecond coherent spike on top of a wide pedestal, which is a typical characteristic of an NLP 59 , 60 . As such, in order to verify the operation regime of the generated pulse, the autocorrelation (AC) measurement was performed.…”

Experimental study of non-stationary operation of a dual-wavelength passively mode-locked fibre ring laser

“…Experimental study of non-stationary operation of a dual-wavelength passively mode-locked fibre ring laser a passive mechanism; this means that by its own architecture, the laser does not need an electronic device to modulate the gain and losses in the cavity in order to produce pulses. The most common passively mode-locked fibre laser (PML-FL) architectures have a configuration of figure eight [9,10] and ring [11,12]. The present work focuses on the latter.…”