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With Co ~ (2 +): Of Lamgal <sub> 11 </ Sub> O <sub> 19 </ Sub> Crystal As A Saturable Absorber Body 1.34m Passively Q-switched Laser

Posted on:2008-05-17Degree:MasterType:Thesis
Country:ChinaCandidate:P LiFull Text:PDF
GTID:2208360212493277Subject:Optical Engineering
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The laser of nearby 1.34μm wavelength is identical with the low dispersive and low loss wavelength of silicon optical fibers. Therefore, it coincides with the transmission window of silicon optical fibers and the frequency-doubling of these lasers supplies an effective way to generate red lasers, so there are widespread application fields for the lasers operating nearby 1.34μm in laser medicine, optical fiber communication, optical sensing locating and the pump source of medial infrared optical parametric oscillation. The laser pulses with short pulse duration and high peak power can be generated in the laser systems of robust, compact structure and low cost by using passive Q-switching technology. These passively Q-switched lasers have many important applications in the fields of time-of-fiight range finding, radar detection, remote sensing, laser machining, etc. The Co2+:LaMgAl11O19 crystal (abbreviation Co:LMA) can be used as saturable absorber in the lasers with output wavelength ranging from 1.3μm to 1.6μm, because it possesses good mechanical properties, high chemical stability and large ground state absorption (GSA) cross-section.In this paper, using Co:LMA as the saturable absorber and Xenon flash-lamp as the pump source, the passive Q-switching of 1.34μm wavelength lasers of the Nd:GdVO4 and the different Gd/Y Nd:YxGd1-xVO4 crystals is realized, and the performance of the output pulses is investigated. Based by the theory of passive Q-switching, the ground-state and excited-state absorption cross-section of two different Co:LMA crystals are measured. The contents of this dissertation can be outlined as follows:1,The development of all-solid-state laser and the passive Q-switching technology, the comparison of several kinds of laser crystal properties and the properties of the Q-switch Co2+:LaMgAl11O19 crystal are introduced.2,Considered the spatial distributions of intracavity photon density, the population inversion density of the gain medium and the ground state and excited state population densities of the saturable absorber, the rate equations and their solutions for passively Q-switched lasers are introduced. The saturable absorption properties of Co:LMA are investigated by experiments, and the 1.34μm ground-state and excited-state absorption cross-sections of Co:LMA are calculated.3,Nd:GdVO4 crystal has attracted a great deal of attentions as a laser crystal for its advantages. In this paper, we have demonstrated the static output performance of a flash-lamp-pumped a-growth Nd:GdVO4 laser operating at 1.34μm with the output mirrors of different transmissions, and the optimum output coupler transmission has also been discussed. The passive Q-switching at 1.34μm with Co:LMA as saturable absorber is realized by focusing in a plano-concave laser cavity. By the theoretical analysis, we can get that the distributions of the oscillating Gauss beams in the resonator vary with the variation of the cavity length. So theαfactor which denote whether the passive absorber can rapidly saturate or bleach into a high transmission state varies with it. Therefore, we can get the single output pulses with larger energy. With the cavity length of 16.3 cm and pump energy of 19.8J, the single-pulse output energy, pulse width and peak power are obtained to be 4mJ, 80ns and 5×104W, respectively. The experimental results agree with the theoretical analysis.4,There are relatively few papers about the relatively new Nd:YxGd1-xVO4 laser crystal in domestic and overseas magazines. In this dissertation, by using the different Gd/Y Nd:YxGd1-xVO4 mixed crystals as the laser crystal and Co:LMA as the Q-switch, the static and dynamic 1.34μm laser output performance pumped by Xenon flash-lamp is investigated with different transmissions of output couplers. When the second threshold condition of passive Q-switching is satisfied, with the cavity length of 245mm and pump energy of 24.2J, the single-pulse output energy, pulse width and peak power are obtained to be 3.5mJ, 45ns and 77.8kW, respectively.By the theoretical and experimental research, we have a better understanding for the Q-switched material: Co:LMA crystal. These supply us useful contributions for getting the laser pulses with shorter pulse duration and larger peak power by designing the optimum resonator structure, and there are some instructional significance and application values for medial and high power 1.34μm passively Q-switched all-solid-state laser.
Keywords/Search Tags:Passive Q-switching, Co2+:LaMgAl11O19 crystal, 1.34μm, flash-lamp pump
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