Environmentally robust all-polarization-maintaining random fiber laser of a cylindrical vector beam

Random lasers with vector modes have garnered widespread attention due to their unique polarization and phase properties and the absence of cavity-defined longitudinal modes. In this work, we propose and demonstrate an all-polarization-maintaining (PM) random fiber laser (RFL) based on a half-open cavity that can simultaneously generate linearly polarized fundamental modes and higher-order modes. Then a cylindrical vector beam (CVB) of azimuthal polarization is generated by the mode superposition method with mode purity exceeding 93.4%. The mode conversion process is realized with a homemade long-period fiber grating and a fiber Bragg grating based on a PM few-mode (FM) fiber. The proposed compact and simple all-PM random laser is capable of generating a CVB without polarization controllers; thus, the environmental stability and self-starting ability will be greatly improved. This laser scheme will be beneficial for the design of vector mode random lasers and is expected to find diverse applications in modal division multiplexing systems, time-domain ghost imaging, and secure communication.