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 (LG00)) mode laser. A laser beam with a conventional Gaussian distribution was obtained for the first time at ~ 7 W output power level (the M2 factors were 3.3 and 1.1 in the horizontal and vertical directions, respectively). CW vortex lasers (LG0+1 and LG0-1) 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.