Real-time observation of pulsating period-doubled vector solitons in a passively mode-locked fiber laser

Abstract

Dissipative solitons (DSs) are self-organized localized structures in non-conservative systems, which require a continuous energy exchange with external sources. In addition to parameter-invariant stationary DSs, there exists a variety of dynamical ones manifesting breathing behaviors. Such intriguing phenomena, termed as soliton pulsations, have been widely studied in recent years under the impetus of advances in real-time spectroscopy. Here, we experimentally investigate various pulsating period-doubled solitons (PDSs) in a fiber laser mode-locked by single-wall carbon nanotubes. Both single- and double-periodic PDS pulsations are found in the cavity. Thanks to the emerging dispersive Fourier transform technique, the polarization-resolved transient spectra of these pulsating PDSs are measured. It is shown that their polarization ellipses rotate with a period of two cavity roundtrips. Moreover, the intensity-modulation behaviors of the two orthogonal polarization components in the odd (even) roundtrips are always asynchronous, which confirms additional slower polarization modulations. Especially, we demonstrate that three combined intensity-modulation periods are involved in the double-periodic PDS pulsation process for the first time, to the best of our knowledge. Our results would stimulate further research on the vector features of multiple-period pulsating solitons in mode-locked fiber lasers.

Paths from stationary to chaos in passively mode-locked fiber lasers: research progress of soliton pulsations and soliton explosions

“…Although soliton pulsations in passively mode-locked fiber lasers have been predicted theoretically for a long time, early experiments could only study soliton pulsations through the periodic change of pulse energy in the oscilloscope track, and the evolution process could not be studied in depth due to detection resolution limits. Scientists have been using the DFT technique to examine the real-time shot-to-shot spectrum evolution of soliton pulsations in nonlinear polarization rotation (NPR) [86,88,[98][99][100][101][102][103][104], NALM [105], nonlinear multimode interference (NL-MMI) [106,107], SWCNTs [85,[106][107][108][109][110][111][112][113][114][115], SnSe [116], graphene [117] passively mode-locked fiber lasers and hybrid mode-locked fiber laser [87,118] till recently. As shown in figure 5, the pulse shape, width, and amplitude of solitons can be periodically altered by simply adjusting the pump power and the angle of the polarization controllers (PCs).…”

Multi-port real-time observation for ultrafast intracavitary evolution dynamics

“…Period-doubling bifurcation. Under certain conditions, the soliton of the fiber lasers can exhibit period-doubling bifurcation [38][39][40] . Although lots of work have revealed many characteristics of the Fig.…”

“…After 4500 RT, the period-doubling bifurcation process becomes stable. The round-trip-resolved field autocorrelation function (ACF) calculated from the inverse Fourier transform of the single-shot spectra measured by the DFT technique 40,41 shows the output is a single soliton. The zoom-in image of 4900~4950 RT shown in the inset demonstrates the process of alternating the pulse width every other round trip, which indicates that the laser operates in a period-2 state.…”

Spatio-spectral dynamics of soliton pulsation with breathing behavior in the anomalous dispersion fiber laser

“…A variety of soliton transient dynamics was observed in passively mode-locked fiber lasers adopting the DFT technique: the build-up of dissipative soliton pulsation, [14] successive soliton explosion, [15] explosion induced rogue waves. [16] Breathing behavior of dissipative soliton pulsation, [17][18][19] multiple soliton pulsation, [20,21] dissipative soliton explosion [22] and the pulsating soliton molecule [23] are observed in the normal dispersion NPR mode-locked fiber laser by the DFT. In the anomalous dispersion region, the soliton pulsation with chaotic behavior [24] and the soliton pulsation sideband characteristics [12] are also studied.…”