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Nd: Luvo <sub> 4 </ Sub> Crystal Performance And Ld End-pumped Microchip Lasers

Posted on:2006-12-25Degree:MasterType:Thesis
Country:ChinaCandidate:L L MaFull Text:PDF
GTID:2208360155966633Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Diode-Pumped Solid-State Laser (DPSSL) have been widely applied in many fields such as medical treament, military, industry, scientific reseaches and so on, due to the advantage of high efficieny, good beam quality, high stability, simple structure, and compactness. The exploration of new laser material is one of the most important part of the reseaches and development of all solid-state lasers. orthovanadates, one of the most excellent laser meterials applied now,such as Nd:YVO4 and Nd:GdVO4 which have particular luminescence properties give rise to much better laser efficiencies when they are pumped by diode lasers than does Nd:YAG.Nd: LuVO4 ,a new laser crystsal, the substitution of lutetium ions (Lu3+) for yttrium (Y3+) or Gadolinium (Gd3+) as constitutive ions in the host materials has already proved to be beneficial .Nd-doped lutetium vanadate single crystals grown by Czochralski method,compared with Nd:YVO4 and Nd:GdVO4 crystal, Nd: LuVO4 offers many advantages such as a broader absorption bandwidth, a larger stimulated emission cross it is more suitable for use as the gainmedium of. a diode laser-pumped solid -state laser.Nd: LuVO4 belong to point group 4/mmm (D4h,) and space group D4h19-I4I/amd. It was grown by the cooperate of Japanese and Muscovite scientists in 1996. C. Maunier grew Nd: LuVO4 by using the flux technique in 2002 ,and perform the laser outout at 1065nm .Our team grew high quality Nd: LuVO4 crystal by Czochralski method, and report on cw and actively Q-switched laser performance achieved under high-power diode pumping. 12.55W of cw output power was obtained with 25W of pump power, giving an optical conversion efficiency of 50.2 % .In actively Q-switched operation ,the average output power reached5.42W with 18W of pump power under crystal, giving an optical conversion efficiency of 30.1 % .This dissertation has made systematic reseaches on the laser properties of Nd: LuVO4 laser crystals in low-power DPSSL, andmade comparision with Nd: GdVO4 crystals.Then GaAs crystals have been used in Q-switched laser experiences,in order to develop new DPSSL devices. The main contents are as follows:1. The main properties ,advantages, applications and developments of DPSSL were introduced briefly.Several typical solid-stated laser materials were summarized. Some important orthovanadate crystals was also introduced.2. The structure and general properties of both Nd:LuVC>4 and Nd:GdVC>4 crystals were introduced briefly. A comparision was also made between two kinds of crystals. Many properties of Nd:LuVO4 crystal, as well as its structure, are smilar to those of Nd:GdVO4 crystal. The difference are that absorption bandwidth and stimulated emission cross section of Nd:LuVO4 crystal are broader and larger than those of Nd:GdVO4 crystal, the thermal conductivity of Nd:LuVC>4 crystal is lower than that of Nd:GdVO4 crystal and higher than that of Nd:YVO4 crystal. So it can proved that Nd:LuVC>4 crystal is an excellent laser meterial.The fluorescence and polarized absorption spectra of Nd:LuVO4 crystal at room temperature were respectively.Compare with those of Nd:GdVC>4 crystal ,both of them have similar anisotropic absorption, absorption and emission peak wavelengths and relative intensity.3. Using synchrotron radiation X-ray topography and chemical etching method, the growth defects in Nd:LuVO4 crystal was investigated. The results of the observations and discussion of growth defects and formations mechanisms in Nd:LuVC>4 crystal was discussed in the dissertation. The main defects were dislocations, sub-grain boundaries, step faceting, inclusions, color centers, and scattering. Sub-grainboundaries is the most important extended defects in crystals. It maybe derives from seed, crystal growth and crystal processing (cutting and polishing). It is essential prerequisites to control the dislocation generation for the application of crystals for technical devices. In order to avoid or decrease these defects, we take some corresponding steps according to the analysis of the defects formation mechanism.4. To determine the structure of Nd:LuVC>4 crystal, the Raman spectra with different configurations was studied. The similar of three orthovanadates stucture by comparing with Raman spectra of Nd:YVO4 and Nd:GdV(>4 crystals was analyzed.5. Based on space-dependent rate equation analysis, the output characteristics of DPSSL were theoretically analyzed, the analytical expressions of the output power, threshold pump power and slope efficiency were derived respectively. The optimum laser crystal length and output coupler were also analyzed based on the expressions,and discussed the criteria for the mode size of microchip.6. We report on cw and passive GaAs Q-switched laser performance achieved with Nd:LuVC>4 and Nd:GdVO4 crystal under low-power diode pumping. The measured output power of Nd:LuV04 vs. the pumping power under different Nd3+ concentrations, different length and different output coupler respectively was investigated, and compared with those of Nd:GdVO4 crystals. The experiments shoe that the highest output power of Nd:LuVO4 is 923mW at 1065nm was obtained at the pump power of 2W with an optical conversion efficiency of 52%.In passive Q-switched operation, the average output power of Nd:LuVO4 reached 0.426W at a pulse repetition frequency (PRF) of 100 kHz with 2 W of pump power incident upon the Nd:LuVC>4 crystal, giving an optical conversion efficiency of 21.3%. The pulse energy and peak power reached 4.3jaJ and 23.2W, the pulse duration was 180ns. the average output power of Nd:GdVO4 reached 0.248W at a pulse repetitionfrequency (PRF) of 100 kHz with 2 W of pump power incident upon the Nd:LuVO4 crystal, giving an optical conversion efficiency of 12.4%. The pulse energy and peak power reached 2.14pJ and 9.1W, the pulse duration was260ns.
Keywords/Search Tags:Nd-doped lutetium vanadate, end-pump, microchip, cw laser, passive Q-switched
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