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Pulsation is a universal phenomenon in all disciplines of nonlinear science, which generally exhibit various nonlinear soliton dynamic modes in nonlinear optics. With the emergence of real-time spectral measurement technology, a new phenomenon of optical soliton pulsation, "invisible" soliton pulsation, has gradually attracted researchers' attention. In this paper, by solving the coupled Ginzburg–Landau equation, we have discovered the partially "invisible" pulsation phenomenon of asymmetric soliton molecules (SMs) composed of two unequal-intensity pulses in a normal-dispersion Mamyshev oscillator for the first time. It is indicated that the fluctuation periods of each internal pulse in asymmetric SMs in terms of peak power, energy, and relative phase difference are all four roundtrips. However, the oscillation period of asymmetric SMs energy is two roundtrips, only half of the above period. Further research shows that the oscillation of the relative phase difference between two internal pulses in SMs is related to the variation of their intensity difference, which can also affect the position change of the spectral modulation peak. This work will enrich the research on "invisible" soliton pulsation and is of great significance for promoting the development of nonlinear dissipative systems. • We studied the pulsating dynamics of soliton molecules in a Mamyshev oscillator. • We discovered the partially "invisible" pulsation of asymmetric soliton molecules. • The total energy period of asymmetric soliton molecules is half of each inside pulse. • The "invisible" pulsation is caused by the intensity difference of the inside pulses. [ABSTRACT FROM AUTHOR]

Mamyshev oscillators (MOs), a new type of femtosecond fiber laser, can produce not only high-performance stationary dissipative solitons (SDSs), but also exhibit chaotic dynamics. Since chaotic behavior may lead to dramatic degradation of the performance, it is particularly important to investigate chaotic dynamics in MOs. Here, using numerical simulation and experimental research methods, we systematically investigate different routes from SDSs to chaos in an MO. Specifically, by simply increasing the gain saturation energy under different polarization states, we obtained different routes from SDSs to chaos, including via a cascade of period-doubling bifurcations (CPDB), via a quasi-cascade of period-doubling bifurcations, and via a double CPDB. In addition, the evolution from dissipative soliton molecules to chaos via CPDB was also observed by increasing the gain saturation energy with a small filter wavelength separation. This finding shows that the evolution from SDSs to chaos is a generic property of laser systems and can appear in various pulse patterns such as single pulse, dissipative soliton molecules, and harmonic mode-locking pulses, which may be beneficial for better understanding chaotic dynamics in MOs. • We investigate different routes from stationary to chaos in a Mamyshev oscillator. • By increasing the gain, we obtained different routes from stationary to chaos. • The evolution from dissipative soliton molecules to chaos was also observed. • The period-2 harmonic mode-locking pulses have also been observed for the first time. • The experimental results qualitatively agree well with the numerical results. [ABSTRACT FROM AUTHOR]

The 1500-km-long Jiangnan tectonic belt in China is well known for large outcrops of Proterozoic basement rocks, although the exhumation history of the exposed basement is poorly constrained. The thermochronology of the Sanfang batholith in the southernmost section of this belt was used to constrain the timing and mechanism of exhumation using apatite fission track analysis of granite samples collected along three transects. The results show that the ages of single apatite grains are much younger than the Neoproterozoic crystallization age of the Sanfang batholith. The apparent age v. elevation diagram shows two-stage cooling during the Paleogene and Miocene. The cooling stages are coincident with unconformities between the Paleogene and underlying strata, and between the Neogene and the Paleogene, with movement on high-angle normal faults. A compilation of apatite fission track data from this and previous studies suggests that the batholith was exhumed in the Cenozoic and the timing of rapid cooling is progressively younger to the east as a result of slab rollback leading to Cenozoic back-arc extension. The exhumation of the Sanfang batholith therefore indicates that Cenozoic erosion and extensional tectonics played a key part in exhuming the basement rocks and forming the present architecture of the Jiangnan tectonic belt. [ABSTRACT FROM AUTHOR]