High-energy noise-like pulses and cylindrical vector beam generation in an Er,Yb-codoped mode-locked fiber laser

As required by nonlinear polarization rotation (NPR) mode-locked Er,Yb co-doped fiber laser, high energy noise-like pulses (NLPs) with cylindrical symmetry, namely cylindrical vector beam (CVB), are obtained. The noise-like pulsed CVBs are produced by passing a q-plate with a topological charge of 1/2 positioned at the output port of the laser cavity. In the fiber laser, a stable mode-locking regime is initiated at the threshold input pump power of 1.44 W. As the input pump power is raised to 11.67 W, the duration of the mode-locking pulse packet is prolonged from 458.6 ps to 2.758 ns, and the corresponding average output power is linearly raised from 35 to 253.3 mW with a maximal pulse packet energy of 260 nJ and the pulse repetition rate of 973.5 kHz. We obtain the mode-locked pulses based on the NLP of measuring autocorrelation curves with coherent peaks on a wide base. The produced ultrafast high-energy CVBs (radially polarized and azimuthally polarized) can be potentially used for applications like particle acceleration and light trapping.