Ultrafast all-fiber based cylindrical-vector beam laser

Abstract

Cylindrical-vector beams (CVBs) with axial symmetry in polarization and field intensity are gathering increasing attention from fundamental research to practical applications. However, a majority of the CVBs are generated by modulating light beams in free space, and the temporal durations are far away from the ultrafast regime. Here, an ultrafast all-fiber based CVB laser is demonstrated via intermodal coupling in two mode fibers. In the temporal domain, chirp-free pulses are formed with combined actions of the ultrafast saturable absorption, self-phase modulation, and anomalous dispersion. In the spatial domain, the lateral offset splicing technique and a two mode fiber Bragg grating are adopted to excite and extract CVBs, respectively. The ultrafast CVB has an annular profile with a duration of 6.87 ps and a fundamental repetition rate of 13.16 MHz, and the output polarization status is switchable between radially and azimuthally polarized states. This all-fiber-based ultrafast CVB laser is a simple, low-cost source for diversified applications of nanoparticle manipulation, high-resolution imaging, material processing, spatiotemporal nonlinear optics, etc.