High energy noise-like pulsing in a double-clad Er/Yb figure-of-eight fiber laser

Abstract

In this work, we study a 215-m-long figure-of-eight fiber laser including a double-clad erbium-ytterbium fiber and a nonlinear optical loop mirror based on nonlinear polarization evolution. For proper adjustments, self-starting passive mode-locking is obtained. Measurements show that the mode-locked pulses actually are noise-like pulses, by analyzing the autocorrelation, scope traces and the very broad and flat spectrum extending over a record bandwidth of more than 200 nm, beyond the 1750 nm upper wavelength limit of the optical spectrum analyzer. Noise-like pulsing was observed for moderate and high pump power preserving the same behavior, reaching pulse energies as high as 300 nJ, with pulse durations of a few tens of ns and a coherence length in the order of 1 ps. Stable fundamental mode locking as well as harmonic mode locking up to the 6th order were observed. The bandwidth was further extended to more than 450 nm when a 100-m piece of highly nonlinear fiber was inserted at the laser output. The enhanced performances obtained compared to other similar schemes could be related to the absence of a polarizer in the present setup, so that the state of polarization along the cavity is no longer restricted.

Generation of spatio-temporal extreme events in noise-like pulses NPE mode-locked fibre laser

“…First studies of the phenomena go back to 90s [2,3] . Since then it has been demonstrated that lasers generating noise-like pulses possess a very rich and complex dynamics [4][5][6][7][8][9][10][11][12][13][14]. Recent studies suggests that mechanisms of coherence's loss in noise-like pulses mode-locked laser include interplay of modulation instability, parametric instability, cascaded four-wave mixing [15].…”

A Novel Low-Cost Synchronous/Asynchronous Microcontroller-Based Pulsed Laser

“…Because the GUI allows the digital defining of both temporal parameters, pulses with arbitrary periods can be produced. In particular, they can have a period of a fraction of some base value, getting the behavior of those "multiple pulses" in mode-locked lasers [12][13][14][15]. As an example, a train of pulses (T = 2.5 s; f = 0.4 Hz) with half the period of Figure 3a is depicted in Figure 3b.…”

“…Another technique, mode locking, the most important technique for obtaining short and ultrashort pulses, produces pulsing when the phases of the cavity modes are locked together, summing their amplitudes [7][8][9][10] so as to generate one pulse per round trip in the cavity; hence, the period (T) corresponds to the laser cavity length [9,11]. Although in general terms pulsed lasers produce a regular train of pulses (equally spaced, identical or quasi-identical releases of energy), some pulsed lasers have the capability to generate multiple pulses during each round trip, which in some circumstances are uniformly distributed along the whole laser cavity (harmonic mode locking) [12][13][14][15]; in this case, the pulse train period is an integer submultiple of the cavity round-trip time (and the pulse repetition rate, an integer multiple of the cavity fundamental frequency). This behavior is very useful for some applications (telecommunications [16], supercontinuum generation [17], metrology [18], etc.).…”

“…The type of laser emission required for applications (CW or pulsed) depends on the situation: CW lasers are commonly employed in holography [19], spectroscopy [20], surface cleaning [21], orthodontics [22], ophthalmology [11], material processing [23] and so on, whereas pulsed lasers are used in metrology [2,18], micromachining [24], ophthalmology [11,25], supercontinuum generation [9,14], telecommunications [26] and more. In general terms, lasers can be classified considering the kind of lasing medium they employ, such as solid state, gas, dye, fiber optics and semiconductor lasers.…”

Simultaneous emission of noise-like pulse and solitons from a fiber laser

“…This regime, typical of long lasers (10-100 m) and / or subjected to a strong pumping injection, differs radically from soliton regimes. Their high energy, very large spectral width (up to several hundreds of nm) and low temporal coherence make them attractive for applications such as sensors [8], supercontinuum generation [9], nonlinear frequency conversion, or microprocessing of materials such as titanium [10]. In addition, they arouse a growing interest in the search for optical rogue waves.…”