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Coupling between modes is crucial for generating coherent structures and spatiotemporal chaos in optical systems. In an ultrafast fiber laser with birefringence, the stable pulse is viewed as a vector soliton (VS) with two orthogonal modes nonlinearly coupled through the Kerr effect and gain/loss. However, the dynamics of a VS in the presence of linear coupling is unperceived despite linear coupling playing a significant role in various optical systems. Here, it is shown that a local linear coupling between polarization modes in lasers facilitates brand‐new nonlinear states, including stationary, breathing, and chaotic VSs. The observed solitary states can be regarded as emergent phenomena when two particles (polarization modes) in a system have a simple interaction (linear coupling), which are ubiquitous in biology, chemistry, and complex systems. It is found that linear coupling is essential for sustaining the internal balance between two modes within the VS. Chaotic dynamics of VS emerge under weak linear coupling, while the two modes lose trapping due to the birefringence in the absence of linear coupling. This work can offer new insight into the two‐mode nonlinear system and inspire research interests in the intelligent manipulation of ultrashort pulse lasers. [ABSTRACT FROM AUTHOR]

Metafibers, by integrating metasurface at the optical fiber tip, are emerging as the significant optical coupling platforms for nanophotonics and fiber-optic communities. Here, we propose a plasmonic metafiber for converting the fundamental mode to first-order mode in fiber, and as proof of device performance, demonstrate an all-fiber Q-switched cylindrical vector laser using the metafiber. Based on polarization-dependent plasmonic resonance, a polarization-independent mode conversion metasurface is designed theoretically and numerically, fabricated directly on fiber facet, and packaged as an all-fiber component with efficiency up to 21% at 1550-nm band. Using the metafiber in an all-fiber laser, Q-switched azimuthally polarized beam (APB) and radially polarized beam (RPB) are delivered at wavelength of 1548.5 nm with pulse durations from ∼7 to ∼2 μs when pump power increases from 30 to 120 mW. The mode purities of the APB and RPB are 86.5% and 90.7%, respectively. This work outlines a new strategy to integrate metasurfaces into "all-in-fiber" systems and offers a reliable route to construct next-generation laser sources, such as all-fiber ultrafast structured lasers. [ABSTRACT FROM AUTHOR]

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]

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]