The Research Of 100kHz A-O Q-Switched Nd: GdVO₄ Laser

Laser-diode pumped solid-state laser (DPSSL) has developed quickly at home and abroad recent years due to its advantages of compactness, good stabilization, high efficiency and long lifetime. It is an available measure to achieve short pulse width and high peak power by Q-switched DPSSL, which has wide applications in laser ranging, lidar, remote sensing, machining and so on. Nd:GdVO4 has been realized and used gradually due to its higher thermal conductivity, larger stimulated emission cross section and absorption cross section, moderate up-level lifetime and polarized output. What is more, it can retain a short pulse width and high peak power even at very high repetition rates.According to the classical four-level rate equation, laser output power and slope efficiency at threshold pumping and high power pumping are deduced, the influence of the distribution of pump light and oscillation light, also deduced the peak power, laser pulse energy and pulse width for the Q switch laser. At the condition of best matching pump wavelength and crystal absorbed wavelength, the optic-optic conversion efficiency of laser is increasing. At the same time, the influence of cavity length and output transmission on laser output power is researched. Under best matching, an output power of 7.3W at 1063nm, optic-optic efficiency of 50.3% and slope efficiency of 58.5% are obtained at the pump power of 14.5W by means of LD single-end pumped Nd: GdVO 4.The thermal lens focus of the crystal is measured by means of critical thermal stabilized cavity. The function of oscillated light spot in the middle of the crystal and pumped power is built according to thermal lens focus. Under the matching oscillated light spot and pumped light spot, the performance of fundamental mode output in plane-plane cavity, concave-plane cavity and convex-plane cavity, respectively, are simulated and analyzed. It is therefore conclude that mode matching can be improved by changing cavity length; the range of mode matching can be increased by decreasing the thermal effect of crystal; stability range of pump power can be increased and high fundamental mode output power can be obtained by means of compensation to thermal effect in convex-plane cavity. Acousto-optic Q-switching theory is introduced. The effects of cavity length, pumped power and output transmission on pulse width and peak power are analyzed at the repetition rate of 10 kHz ~100 kHz respectively. The influence of above three factors on pulse width and peak power is greater at 100 kHz than 10 kHz. LD single-end-pumped A-O Q-switched Nd: GdVO4 laser has been developed and the laser output of short pulse width at the repetition rate of 100 kHz is obtained. The results at the repetition rate of 100 kHz, pulse width of 19.6ns, average output power of 3.52W and peak power of 1.8kW, have been obtained respectively.