Generation of 435 MHz, Ultrafast Cylindrical Vector Pulses From a Mode-Locked Fiber Laser

Cylindrical vector beams have spawned numerous applications in modern optics. Although cylindrical vector pulses with several tens of megahertz repetition rate can be obtained directly at the laser source with high-purity structured modes, cylindrical vector pulses with hundreds of megahertz or gigahertz repetition rate have greater application prospects in the fields of laser processing and super-resolution imaging. Here, we report on the generation of a repetition-rate of 435.8 MHz, cylindrical vector pulses from a fundamentally mode-locked Yb-doped solid-state fiber laser. The nonlinear-polarization-evolution (NPE) mode-locking and high pump power injection enabled short pulses with high repetition rate, while on-demanded cylindrical vector beams including radially and azimuthally polarized beams were yielded by adjusting the polarization control elements inside the cavity. Mode-locked pulses were delivered with an average power of 315 mW, a spectrum bandwidth of 23 nm, and a pulse duration of 904 fs. To the best of our knowledge, it is the highest repetition rate from a fundamentally mode-locked Yb-fiber laser which directly generates cylindrical vector pulses.