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Research On Laser-Diode End-Pumping High Repetition Rate Electro-Optical Q-switched Nd:GdVO4 Laser

Posted on:2012-02-25Degree:MasterType:Thesis
Country:ChinaCandidate:C WangFull Text:PDF
GTID:2218330362451201Subject:Physical Electronics
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Laser-diode end-pumped solid-state laser (DPSSL) is focused on for its merits of high efficiency, high beam quality, compact structure and so on. Q-switch technology is the key method to obtain pulsed laser, and is widely used in many industrial and military fields such as micro-mechanical machining, laser communication, lidar and so on. Electro-optical Q-switched technology is favorable to get high repetition rate, short pulse width and high peak power laser output, because of its advantages of high speed switching time, high on-off ability and high stablility. Nd:GdVO4 crystal has large absorption and emission cross-section, moderate fluorescence lifetime, high thermal conductivity as well as polarization- laser property, which make it an ideal laser medium under high repetition rate operation. Based on these, this thesis reports the properties of laser-diode end-pumped electro-optical Q-switched Nd:GdVO4 laser, including pulse-reflection mode (PRM) and pulse-transmission mode(PTM, cavity-dumped mode).Firstly, the thesis discusses the laser's mode matching and thermal effect of solid-state laser, which are the crucial ingredients of the laser's power, efficiency and beam quality. According to the relationship between continuous-wave laser power and mode maching, the best ratios of the oscillation mode's size and the pumping mode's size under different pumping powers are deduced. Based on the analysis of the laser's heat-producing mechanism, the thermal lensing effect is studied. Then the relationship between thermally induced diffraction losses and the pump power as well as the cavity mode size is analyzed. Lastly, this thesis studies the controlling and compensation measures for improving thermal effects.According to the rate equations for continous-wave pumped solid-state laser, significant parameters for Q-switched laser, such as pulse width, pulse energy and peak power are inferred. Besides, the optimum coupling reflectivity is also obtained. Under the direction of these theories, this dissertation realizes electro-optial Q-switched 1063 nm Nd:GdVO4 laser output in the experiment. The highest operation repetition rate can reach up to 100 kHz, and the pulse width is 20.2 ns, with a peak power of 3.1 kW. Meanwhile, the superiority of electro-optical Q-switched laser is verified quantitatively compared to acousto-optical Q-switched laser.Lastly, the numerical relationship between the pulse shape of the cavity-dumped laser and the switching time along with the cavity length is established. In the cavity-dumped experiments, a constant 5.5±0.2 ns pulse duration laser is obtained. And the highest repetition rate is 50 kHz, the corresponding peak power is 18.2 kW. In order to scaling the cavity-pumped laser performance, based on the controlling measures for thermal effects, 879 nm laser diode and GdVO4/Nd:GdVO4 composite crystal are employed in the cavity-pumped experiment. And a constant pulse width of 3.8±0.2 ns is realized. The maximum average output power of 13.3 W is realized at 80 kHz. At repetition rates of 10 kHz, 50 kHz and 100 kHz, the corresponding peak powers are 252.6 kW, 65.9 kW and 34.4 kW, respectively.
Keywords/Search Tags:DPSSL, Nd:GdVO4, electro-optical Q-switched, cavity-dumped
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