Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, which was fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microfiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band. The microfiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By integrating this optical SA device into an erbium-doped fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm. The prevention of BP from oxidation through the “lateral interaction scheme” owing to this microfiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP. Our results not only demonstrate that black phosphorus might be another promising SA material for ultrafast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microfiber.

We report on the generation of passive harmonic mode locking of a fiber laser using a microfiber-based topological insulator (TI) ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ saturable absorber (SA). The optical deposition method was employed to fabricate the microfiber-based TISA. By virtue of the excellent nonlinear optical property of the proposed TISA, the fiber laser could operate at the pulse repetition rate of 2.04 GHz under a pump power of 126 mW, corresponding to the 418th harmonic of fundamental repetition frequency. The results demonstrate that the microfiber-based TI photonic device can operate as both the high nonlinear optical component and the SA in fiber lasers, and could also find other applications in the related fields of photonics.

We report on the generation of a femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based molybdenum disulfide (${\mathrm{MoS}}_2$) saturable absorber (SA). With a saturable optical intensity of $34\mathrm{MW}/{\mathrm{cm}}^2$ and a modulation depth of $\sim 4.3\%$, the PVA-based ${\mathrm{MoS}}_2$ SA had been employed with an erbium-doped fiber ring laser as a mode locker. The mode-locking operation could be achieved at a low pump threshold of 22 mW. A $\sim 710\mathrm{fs}$ pulse centered at 1569.5 nm wavelength with a repetition rate of 12.09 MHz had been achieved with proper cavity dispersion. With the variation of net cavity dispersion, output pulses with durations from 0.71 to 1.46 ps were obtained. The achievement of a femtosecond pulse at 1.55 μm waveband demonstrates the broadband saturable absorption of ${\mathrm{MoS}}_2$, and also indicates that the filmy PVA-based ${\mathrm{MoS}}_2$ SA is indeed a good candidate for an ultrafast saturable absorption device.

We reported on the generation of femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based topological insulator (TI), Bi₂Se₃ saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm² and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device.

A simple configuration for the generation of tunable multiwavelength picosecond-pulse fiber ring lasers by exploiting the intracavity birefringence-induced comb filter is demonstrated. The fiber laser is passively mode locked by using nonlinear polarization rotation (NPR) technique. The polarization-dependent isolator combined with the intracavity birefringence acts as two functions: the tunable comb filter and the mode locker. Up to four-wavelength picosecond pulses were simultaneously obtained in the experiment. The mode competition of the multiwavelength lasing is suppressed by the use of NPR-induced intensity-dependent loss. In addition, the number of the lasing wavelengths, the lasing location, and the spacing between the lasing wavelengths could be flexibly tuned by properly rotating the polarization controllers.

Soliton explosions, as one of the most fascinating nonlinear phenomena in dissipative systems, have been investigated in different branches of physics, including the ultrafast laser community. Herein, we reported on the soliton dynamics of an ultrafast fiber laser from steady state to soliton explosions, and to huge explosions by simply adjusting the pump power level. In particular, the huge soliton explosions show that the exploding behavior could operate in a sustained, but periodic, mode from one explosion to another, which we term as “successive soliton explosions.” The experimental results will prove to be fruitful to the various communities interested in soliton explosions.