We demonstrate the quasi-continuous-wave long-pulsed operation of a compact all-solid-state modeless laser based on intracavity frequency-shifted feedback by an acousto-optic modulator. The laser active medium is an Nd:YAG crystal rod, side-pumped by high-brightness laser diodes of 808 nm. When the pump repetition and duration are 200 Hz and 250 μs, the maximum single pulse energy of 85 mJ is produced at an optical conversion efficiency of ~34%, and also a good beam quality of M<sup>2</sup> <sub>X</sub> = 1.80 and M<sup>2</sup> <sub>Y</sub> = 1.78 is obtained in the horizontal and vertical directions respectively. Moreover, a narrow continuous spectrum is achieved with the 3-dB linewidth of 75 pm (i.e. 20 GHz) and the center wavelength of 1064.16 nm. Via the sum frequency generation, such a long-pulse (several hundred μs), narrow-linewidth modeless laser source is preferred for solving the major problem of saturation of the mesospheric sodium atoms and can create a much brighter sodium guide star to meet the needs of adaptive imaging applications in astronomy.
A high-power tunable Littrow grating external-cavity tapered semiconductor laser is designed in this paper. By using the grating external cavity to lock the wavelength and narrow the linewidth, we gained a series of single-frequency laser with the central wavelength at 927 nm, tunable range >20nm and linewidth < 980 fm with the continuous pumping. When the wavelength is 926.8 nm, the threshold current is 1.25A and the oblique efficiency is 0.682 W/A. When the injection current increases to 4A, the maximum output power is up to 1.906W, with the electro-optic efficiency of 21.7%, the linewidth of 700fm, and the beam quality of 1.948 and 3.788 in the fast and slow axis respectively.
The amplifier experiment research of end-pumped long pulse slab laser is developed, the results of out-put energy, optical-optical efficiency and pulse waveform are obtained at different experiment conditions, such as peak pumped power, amplifier power and pumped pulse width. The seed laser is CW fundamental transverse-mode operation fiber laser, the laser medium is composited Nd:YAG slab. Under end-pumped and the 2 passes, the laser obtain 7.65J out-put energy and 43.1% optical-optical efficiency with 45kW peak-pumped power and 386μs pump pulse width. The experimental results provide the basic for the optimization design to high frequency, high energy and high beam-quality slab lasers.