High power and high beam quality continuous wave Tm:YLF laser by the dual-end-pumped is presented in this letter. The highest output power reaches 21.3 W when the totally input pump power is 54.6 W. The optical conversion efficiency is 39.0% and the slope efficiency is 47.3%. With an F-P etalon in the cavity, the output center wavelength is tuned to 1908 nm with about 0.5 nm FWHM. With the optimal cavity, the beam quality factor M 2 can be ∼ 1.1. As we know, our work is the first time to investigate the Tm:YLF laser output spectrum with an F-P etalon in the cavity, and acquire near-diffraction limited laser output. Output power, W 25 20 15 10 5 0 60 50 40 30 20 10 0 Incident pumped power, W

The aim of this work is to investigate the effects of different power modes [constant current (CC), constant voltage (CV) and constant power (CP)] on the structure and corrosion resistance of the plasma electrolytic oxidation ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology and element distribution of the coatings were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings in the simulated body fluid was examined by electrochemical impedance spectroscopy and polarisation curve methods. The results showed that the coatings were of porous structure and mainly composed of MgO. The thickness, surface roughness, the size of the surface micropores and the amount of MgO were all increased with the cell voltage under the same power mode or increased in the sequence CV.CC.CP under the different power modes. The corrosion resistance of coatings was related to the structure characteristics, which were determined by different power modes. Among the different power modes, the corrosion resistance of the coatings is generally increased in the sequence CV.CP.CC, and under the same mode, the proper increase in the cell voltage is liable for improving the corrosion resistance of the coatings.