LD-pumped high-power CW Pr3+:YLF Laguerre-Gaussian lasers at 639 nm

Based on a lowly-doped (0.12 at. %) Pr3+:YLF crystal, high-power continuous-wave (CW) lasers at 639 nm were obtained by laser-diode (LD) pumping. A maximum output power of 8.14 W with a total slope efficiency of 51.5% was achieved for the quasi-fundamental (or called quasi-zero-order Laguerre-Gaussian (LG(0)(0))) mode laser. A laser beam with a conventional Gaussian distribution was obtained for the first time at similar to 7 W output power level (the M-2 factors were 3.3 and 1.1 in the horizontal and vertical directions, respectively). CW vortex lasers (LG(0)(+1) and LG(0)(-1) ) with a maximum output power of 6.03 W were achieved by off-axis pumping. The total slope efficiency of the vortex laser was 56.3%. To the best of our knowledge, the output powers of the two types of lasers are the highest to date. Furthermore, theoretical models were built to explain the input-output power characteristics of the results and provide guidance to design high-power Laguerre-Gaussian lasers.