  Ultrafast lasers generating high repetition rate ultrashort pulses through
various mode-locking methods can benefit many important applications including
communication, materials processing, astronomical observation, etc. For
decades, mode-locking based on dissipative four-wave-mixing (DFWM) has been
fundamental in producing pulses with repetition rates on the order of gigahertz
(GHz), where multiwavelength comb filters and long nonlinear components are
elemental. Recently, this method has been improved using filter-driven DFWM,
which exploits both the filtering and nonlinear features of silica microring
resonators. However, the fabrication complexity and coupling loss between
waveguides and fibers are problematics. In this study, we demonstrate a tens to
hundreds of gigahertz stable pulsed all-fiber laser based on the hybrid
plasmonic microfiber knot resonator device. Unlike previously reported pulse
generation mechanisms, the operation utilizes the
nonlinear-polarization-rotation (NPR) effect introduced by the
polarization-dependent feature of the device to increase intracavity power for
boosting DFWM mode-locking, which we term NPR -stimulated DFWM. The
easily-fabricated versatile device acts as a polarizer, comb filter, and
nonlinear component simultaneously, thereby introducing a novel application of
microfiber resonator devices in ultrafast and nonlinear photonics. We believe
that our work underpins a significant improvement in achieving practical
low-cost ultrafast light sources.
