We present a passively mode-locked erbium-doped fiber ring laser with near-zero net cavity dispersion using the nonlinear polarization rotation technique. The compact all-fiber laser is constructed by utilizing an optical integrated component. Through optimizing the cavity dispersion and nonlinearity, high-peak-power near-transform-limited pulses with a spectral width beyond the gain bandwidth limitation can be directly obtained from the laser. Resultant output pulses have a pulse duration of 62 fs, a 3-dB spectral width of 66.3 nm, and a maximum peak power of 7.9 kW. Numerical simulations reproduce the generation of sub-100-fs pulses in the laser. The pulse-shaping mechanism can be attributed to simultaneous dispersion and nonlinearity management in the cavity, which is distinct from that in the stretched-pulse lasers.
We present a numerical investigation of dissipative-soliton-resonance (DSR) generation in an all-normal-dispersion Ybdoped fiber laser mode-locked by a real saturable absorber (SA). In the simulation model, the SA includes both the saturable absorption and excited-state absorption (ESA) effects. The intra-cavity pulse evolution is numerically simulated with different transmission functions of SA. When omitting the ESA effect, the transmissivity of SA increases monotonically with the input pulse power. The noise-like pulse (NLP) operation in the cavity is obtained at high pump power, which is attributed to the spectral filtering effect. When the ESA effect is activated, higher instantaneous power part of pulse encounters larger loss induced by SA, causing that the pulse peak power is clamped at a certain fixed value. With increasing pump, the pulse starts to extend in the time domain while the pulse spectrum is considerably narrowed. In this case, the NLP operation state induced by the spectral filtering effect is avoided and the DSR is generated. Our simulation results indicate that the ESA effect in the SA plays a dominant role in generating the DSR pulses, which will be conducive to comprehending the mechanism of DSR generation in passively mode-locked fiber lasers.
We report on ultrafast-pulse generation in an erbium-doped fiber ring laser mode-locked by a graphene/WS<sub>2</sub> van der Waals heterostructure saturable absorber. Atomic-layered WS<sub>2</sub> is first synthesized on SiO<sub>2</sub>/Si substrate by the chemical vapor deposition (CVD) method, and then graphene/WS<sub>2</sub> heterostructure is fabricated by transferring graphene onto the CVD-grown layered WS<sub>2</sub>. Taking advantage of excellent saturable absorption properties of the fabricated graphene/WS<sub>2</sub> heterostructure, stable soliton pulses are successfully generated in the laser with a 3-dB spectral width of 2.3 nm and a pulse duration of 1.12 ps. Numerical simulations reproduce the mode-locked pulse emission in the experiment. Our research provides a new insight for tailoring versatile two-dimensional heterostructures so as to develop ultrafast photonic applications.