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• In this paper, it is reported that the single-longitudinal-mode Er:YAG laser based on the Faraday effect for the first time. • The Er:YAG single-longitudinal-mode laser is amplified to 1.86 W with the double-pass amplifier system. We demonstrate a continuously operating Er:YAG single-longitudinal-mode laser and its amplifier with a corner cube retroreflector based on the Faraday effect. A maximum power of 1.02 W, the central wavelength of 1645.46 nm, Er:YAG single-longitudinal-mode laser with a line-width of 204 kHz has been realized. The slope efficiency is 9.38% and the beam quality factors M2 are 1.16, 1.05 in the × and y directions. Additionally, the single-longitudinal-mode laser is amplified to 1.86 W by the double-pass amplifier. The results indicate that the unidirectional operation ring laser in combination with the corner cube prism provides a 1.6 μm continuous-wave single-longitudinal-mode laser with high-power and stability. [ABSTRACT FROM AUTHOR]

• An LGS electro-optically Q-switched Ho:GdVO4 laser operating at room temperature and directly pumped by LD is firstly reported. • The maximum output energy of 3.25 mJ with a pulse width of 4.2 ns were achieved at PRK of 1 kHz. • The peak power as high as 773.8 kW was achieved. We proposed a Ho:GdVO 4 laser operating at 2.05 µm in-band directly pumped by the 1.94 μm fiber-coupled laser diode, which electro-optically Q-switched by an LGS(La 3 Ga 5 SiO 14) crystal. Adopting 1.0 at.%-doped Ho:GdVO 4 crystal as the gain medium, a maximum output power of 6.5 W at 2047.9 nm with the absorbed pump power of 28 W was obtained in the continuous-wave mode, corresponding to a slope efficiency of 37.6 %. At a pulse repetition frequency of 1 kHz, the highest pulse energy of 3.25 mJ with a pulse width of 4.2 ns was achieved, corresponding to a peak power of 773.8 kW. In addition, the beam quality factor M2 was measured to be 1.9 at the maximum output level by the 90/10 knife-edge method. TEM 00 propagation has been verified by a camera. To the best of our knowledge, this is the first demonstration of high peak power electro-optically Q-switched Ho:GdVO 4 laser directly pumped by the 1.94 μm laser diode. [ABSTRACT FROM AUTHOR]

• High efficiency laser ultrasound of carbon fiber reinforced plastics is developed based on an annular distributed laser excitation source with wavelength of 2.09 µm. • The maximum ultrasound signal amplitude higher than 280 mV was realized. In this paper, we demonstrate a high-efficiency laser ultrasound in carbon-fiber-reinforced plastics (CFRP) by means of excitation laser spatial distribution modulation. The maximum ultrasound signal amplitude of about 286 mV was achieved by directing an annular laser with wavelength of 2090 nm, energy of 2.5 mJ and pulse width of 16 ns onto CFRP samples. The ultrasonic signal amplitude excited by annular laser is more than one times higher than that by typical Gaussian laser under the same conditions. Also, for CFRP laser ultrasound excited by annular laser, the intensity of ultrasound increased in different frequency components as a whole with increasement of laser energy density. The results indicated that it is an effective technical way to improve photo-acoustic efficiency and amplitude of the ultrasonic signal by shaping 2 μm region excited laser spatial distribution into annular type in the CFRP laser ultrasound. [ABSTRACT FROM AUTHOR]