High-energy noiselike rectangular pulse in a passively mode-locked figure-eight fiber laser

Abstract

We report on the generation of a high-energy noiselike rectangular pulse in a mode-locked figure-eight fiber laser. The noiselike pulse appeared to have a rectangular shape on the oscilloscope. The pulse duration increased with increasing pump power, while the peak amplitude remained constant, which is very similar to the pulse evolution of dissipative soliton resonance. However, the pulse type is confirmed as a noiselike pulse using an autocorrelator. With the maximum pump power of 350 mW, the 135 nJ noiselike rectangular pulse with 76 ns duration was achieved. The results provide a new guideline for clarifying an alternative formation mechanism of the high-energy rectangular pulses in fiber lasers.

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

“…In this work, using a F8L scheme including a polarization-imbalanced NOLM without polarization control, NLPs with quite remarkable properties were produced. Firstly, in spite of the low laser efficiency, stable single-pulse energies as high as 300 nJ were obtained, which is to the best of our knowledge the highest NLP energy directly at the laser output reported to date [7,[12][13][14]. In particular, splitting into multiple pulses, which usually restricts maximal NLP energy as pump power is raised in polarization-controlled schemes [7], was not found to be a limiting factor in this case.…”

“…Such splitting has been observed in ring cavities with a polarizer, including kmlong designs [7,39], but also a much shorter setup [40], even though the pump powers were much lower than in this work. On the other hand, previous record-high NLP energies were obtained using long figure-eight lasers without polarizing element; no pulse breaking or multiple pulsing was observed with these schemes [13,14]. In terms of bandwidth, although light propagation through km-long cavities should favor spectral broadening through nonlinear processes such as stimulated Raman scattering, record-low NLP bandwidths of a few nm were reported in [7,39], which include a polarizer.…”

“…First demonstrated by Horowitz et al [8], this particular regime of fiber lasers has been drawing attention due to its potential for generating very broad spectra covering hundreds of nanometers [9][10][11], for achieving high energy pulses [7,[12][13][14] and for applications requiring low temporal coherence [8]. NLPs are partially stationary pulses consisting of a bunch of extremely variable ultrashort sub-pulses conserving stable global properties like the total duration of the bunch, its average amplitude, energy and average spectrum.…”

“…For example, some authors have reported that changing the pump power affects the energy and the width of the bunch without modifying the average peak power of the pulse or the shape of the optical spectrum [16,19,20]; others observed that, beyond certain duration, a NLP tends to split into multiple pulses as pump power is increased [7]. In terms of pulse energies, high values up to 250 nJ have been reached without pulse breaking [7,[12][13][14].…”

“…Besides, NLPs have been observed in various spectral windows including EDF [6][7][8][9][10][11]13,16,20], YDF [21] and TDF [14,22]. Another remarkable aspect of NLPs is that they have demonstrated better efficiency than solitons in nonlinear processes such as cascaded stimulated Raman scattering [23], nonlinear frequency conversion [23,24] and supercontinuum (SC) generation [25,26], among others.…”