Generation of multi-solitons and noise-like pulses in a high-powered thulium-doped all-fiber ring oscillator

Abstract

We report a study on the switching of the generation regimes in a high-powered thulium-doped all-fiber ring oscillator that is passively mode-locked with nonlinear polarization evolution technique with different pumping rates and cavity dispersion values. In one experimental setup, switching was observed between the noise-like pulse and the multi-soliton (in the forms of soliton bunches and soliton rain) regimes by the adjustment of the intracavity polarization controllers. We attributed this to the crucial influence of the nonlinear polarization evolution strength determined by such key parameters as saturation (over-rotation) power, linear phase bias, and nonlinear losses on the pulse evolution and stability. So the soliton collapse effect (leading to noise-like pulse generation) or the peak power clamping effect (generating a bunch of loosely-bound solitons) may determine pulse dynamics. Both the spectrum bandwidth and coherence time were studied for noise-like pulses by varying the cavity length and pump power, as well as the duration of solitons composing bunches. As a result, both noise-like pulses (with spectrum as broad as 32 nm bandwidth) and multi-soliton formations (with individual pulse-widths ranging from 748 to 1273 fs with a cavity length increase from 12 to 53 m) with up to 730 mW average power were generated at a wavelength of around 1.9 μm. The results are important for the realization of the broadband and smooth supercontinuum which can be used as a source for mid-IR vibrational spectroscopy of gas samples for breath analysis and environmental sensing.

Modelocked Tm-doped Fiber Laser Using Multimode Interference Saturable Absorber in Reflection Mode

“…MMI based SAs are particularly desirable for fiber lasers due to their all-fiber design and compatibility for modelocking over a broad wavelength range. In addition to the common generation of a single soliton pulse at cavity roundtrip rate, passive SAs have also enabled generation of other output pulse formats such as noise like pulses (NLP) [5], soliton rain [6] and rogue waves [7]. NLP are modelocked pulses characterized by a duration of the order of the picosecond to nanosecond, with random femtosecond features.…”

Noise‐like pulse generation with tungsten trioxide/polydimethylsiloxane‐clad microfiber saturable absorber

“…Recently, a number of researches have been devoted to multi-pulse generation in mode-locking, such as bound solitons 4 and noise-like pulse (NLP). 5 This multi-pulse operation is enabled by the peculiar interaction among gain, nonlinearity, and cavity dispersion. 6 Unlike the regular pulses, NLP exhibits extraordinary autocorrelation trace that features a narrow inner spike at zero-time delay with randomly varying amplitude and duration on top of a relatively broad pedestal, which is also known as double-scale intensity autocorrelation trace.…”

Twelve-Wavelength-Switchable Thulium-Doped Fiber Laser With a Multimode Fiber Bragg Grating

“…To date, various TDFLs have been proposed, including the TDFL with switchable output [12], [13], TDFL with single-longitudinal-mode operation [14], [15], mode-locked TDFL [16], [17] and high power TDFL [18]. The TDFL with switchable output is extensively used in optical fiber sensing and wavelength routing networks due to its flexible lasing performance.…”