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Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to ~1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets. The coherence degradation of pulses synchronized to optical cavities is an issue for ultrahigh-repetition-rate lasing. Here the authors demonstrate synchronized multi-wavelength mode-locked soliton fiber lasers generating ultrafast outputs from two to five wavelengths with a high sub-pulse repetition rate. [ABSTRACT FROM AUTHOR]

Lead selenide (PbSe) is a new emerging semiconductor with layer-dependent bandgap that has attracted much interest due to its high infrared response and good environmental stability. We have prepared large-scale PbSe films with the area of 7 cm2 and thickness of 25 nm based on physical vapor deposition approach at 160°C. The PbSe films exhibit saturable absorption property at 1.55 μm and a polarization-sensitive saturable absorber is obtained by growing PbSe on D-shaped fiber. Single-pulse with the duration of 490 fs is generated at the pump of 12 mW and the mode-locking operation is maintained at the pump of 1500 mW, indicating the high damage threshold of the D-shaped fiber based saturable absorber. Two polarization-insensitive saturable absorbers are achieved by depositing PbSe on fiber facet and polyvinyl alcohol film, respectively. For fiber facet (polyvinyl alcohol film) based saturable absorber, the repetition rate of Q-switched pulses increases from 8.6 (16.3) kHz to 45.4 (59.2) kHz while the duration decreases from 7.92 (12) μs to 2.06 (3.12) μs by tuning the pump from 15 mW to 90 (60) mW. Such large-scale PbSe films possess features of low cost and high modulation ability, and can find important applications in infrared optical modulators and detectors. [ABSTRACT FROM AUTHOR]

Optical vortices, characterized by helical phase fronts, are usually generated outside the laser cavity using passive modulation methods. Here, we demonstrate an all-fiber laser to directly deliver mode-locked and continuous-wave vortex beams based on modulation of transverse modes in the two mode fiber. The mode couplers and reflectors for three schemes are long period fiber grating (LPFG) and fiber mirror, fiber taper and fiber Bragg grating, and LPFG and fiber Bragg grating, respectively. The laser is switchable between ±1 order vortex operations by tuning the intracavity polarization controller, and the optical vortex can directly work as an optical tweezer to manipulate rhenium diselenide nanosheets. The pulse duration at the mode-locked state is tunable from subpicoseconds to several picoseconds by spectral filters, and the maximum output power at the continuous-wave state exceeds 35 mW. The cost-effective all-fiber vortex laser is quite attractive for research of micromanipulation, spatiotemporal soliton, and optical communication. [ABSTRACT FROM AUTHOR]

In article number 2300076, Yueqing Du, Dong Mao, Jianlin Zhao, and colleagues investigate the vector soliton under linear coupling introduced by a simple polarization controller in the fiber laser. B Emergent Phenomena of Vector Solitons Induced by the Linear Coupling b Vector solitons are ubiquitous in optical systems supporting two modes with nonlinear interactions. [Extracted from the article]