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Ld End-pumped Yvo <sub> 4 </ Sub> / Nd: The Yvo <sub> 4 </ Sub> And Nd: Y <sub> 0.8 </ Sub> Lu, <sub> 0.2 </ Sub> Vo <the Sub > 4 </ Sub> Crystal Q-switched Laser Characteristics

Posted on:2011-03-21Degree:MasterType:Thesis
Country:ChinaCandidate:S G LiFull Text:PDF
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Diode-pumped solid-state pulse lasers with short pulse width and high peak power, which have many merits such as high conversion efficiency, compactness, high stability and long lifetime, have been found in a wide variety of applications in the fields of industry, military, medical treatment and scientific researches. Therefore, developing techniques for Q-switching or mode-locking in diode-pumped lasers has been burgeoning as a new exploration to get compact pulsed lasers for scientific researchers. In the present dissertation, we discussed the technologies of continuous wave operation of fundamental generation, as well as active and passive Q-switching laser properties in diode-end-pumped YVO4/Nd: YVO4 and Nd: Y0.8Lu0.2VO4 solid-state lasers. The central contents have been summed up as below:1. Review of the history and development of all solid state lasers, and the main approaches and new improvements of Q-switching pulse lasers nowadays are summarized. The optical properties of new Nd-doped mixed vanadate crystal Nd: Y0.8Lu0.2VO4 are simply introduced and compared with other isomorphism.2. The thermal effect of laser material and some measures to restrain effectively the thermal lens effect are also introduced. It is demonstrated experimentally that the laser of composite crystal can obviously recede the grads of temperature inside of laser crystal and relieve effectively the lens effect because of end-facet deformation,resulting in higher output power.3. A diode-end-pumped acousto-optic (AO) Q-switched YVO4/Nd:YVO4 composite crystal laser emitting at 1064 nm is demonstrated in our experiment with a comparative simple cavity, and the composite crystal laser can generate short pulse duration and high peak power by optimum design. The shortest pulse width of 9.5 ns and the maximum average output power of 10.12 W are obtained at the repetition rate of 90 kHz, corresponding to an optical conversion efficiency of 37.5 %. A 4.2-ns pulse with 2.9-mJ pulse energy and 691.4-kW peak power has been achieved under 20 W incident pump power at 1 kHz for the output coupler at the transmission of 50%. 4. We investigate the laser properties of a novel mixed Nd: Y0.8Lu0.2VO4 crystal in the present experiment. The expression for diode-pumped solid-state laser characteristics is reached. The thermal effect of Nd: Y0.8Lu0.2VO4 with different parameters for cavity length and output coupler's transmission is explored.5. We present for the first time a diode end-pumped acousto-optic (AO) Q-switched Nd: Y0.8Lu0.2VO4 crystal laser emitting at 1064 nm with a comparative simple planar-planar cavity. In order to prevent thermally induced fracturing from the new crystal, the maximum pump power is kept below 14 W in both continuous and Q-switching operation. The maximum continuous wave (CW) power of 5.61 W is achieved at the incident pump power of 13.07 W, resulting in optical to optical conversion efficiency of 43%. For Q-switching operation, at the incident pump power of 13.07 W, the shortest pulse width is 11 ns at the 1 kHz repetition rate and the output transmission of 50%, the maximum average output power is 4.23 W at 100 kHz and 20% transmission, and the measured highest peak power is 225.45 kW at 1 kHz and the transmission of 50% for the output coupler.6. Employing a set of output couplers to optimize the laser performance, a diode end-pumped passively Q-switched Nd: Y0.8Lu0.2VO4 laser with Cr4+: YAG crystal is first demonstrated in our experiment. The maximum continuous wave (CW) output power of 5.59 W is obtained at the incident pump power of 13.07 W with the output transmission T=20%, resulting in an optical-to-optical efficiency of 42.7%. For Q-switching operation, the measured pulse duration of 8.5 ns and the pulse energy of 45.24μJ are respectively obtained for the output transmission of 50% when the Cr4+: YAG crystal with an initial transmission (T0) of 60% is used.
Keywords/Search Tags:All-solid-state laser, YVO4/Nd: YVO4, Nd: Y0.8Lu0.2VO4, continuous wave operation, AO Q-switching, passive Q-switching, semiconductor saturable absorber, Cr4+: YAG
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