不同Li/Nb比Mg:In:Fe:LiNbO3晶体的光折变性能研究

采用提拉法生长了不同Li/Nb比(Li/Nb=0.85,0.94,1.05,1.20,1.38)的Mg:In:Fe:LiNbO3(LN)单晶.测试了Mg:In:Fe:LN晶体的红外透射光谱,紫外吸收光谱,抗光致散射能力,响应时间和指数增益系数.实验结果显示:Li/Nb=0.85晶体的OH-吸收峰在3481cm-1附近, Li/Nb=0.94、1.05、1.20的晶体的OH-吸收峰在3505cm-1附近,而Li/Nb=1.38晶体的OH-吸收峰有三个,分别在3466cm-1、3481cm-1和3518cm-1附近.随着Li/Nb比的增大,晶体的紫外吸收边发生紫移,抗光致散射能力增强,响应速度加快,指数增益系数增大.结果表明:Li/Nb=1.38的晶体是性能最为优良的光折变晶体材料.     

钐掺杂钨酸铅晶体的生长

为了用提拉法生长出质量优良的衫掺杂钨酸铅晶体,通过理论分析,实践论证,确定了生长晶体的工艺参数.温度梯度采用较成熟工艺,讨论晶体的生长速度和旋转速度.晶体生长速度为2 ～5mm/h;晶体旋转速度为35 ～50r/min;以45℃/h的速度降至室温,同时保持30r/min的旋转速度.得到了不同浓度衫掺杂的表观透明,无碎裂淡粉红色的钨酸铅晶体,且目前得到晶体的最大尺寸为φ25mm×40 mm.     

Study on the Growth and Photorefractive Properties of In：Fe：Cu：LiNbO3 Crystals

Fe(0.2 mol%):Cu(0.04 mol%):LiNbO3 crystals with different doping concentration of In3+ (0, 1.0, 2.0, 3.0mol%) were grown by Czochralski method, and then oxidized and reduced. The infrared transmittance spectra of crystals were measured to investigate the location of doping ion and its threshold concentration. The photorefractive properties of the crystals were tested by two beam coupling experiment. The results showed that the threshold concentration of In ions is 2.0～ 3.0 mol% and In ions take the place of NbL 4i+ to form ( In L2i+) before reaching its threshold concentration, and then the location of normal Nb ions. In the (2.0 mol%):Fe:Cu:LiNbO3 crystal with the oxidation treatment having the highest diffraction efficiency (η = 45.8%), the photo-damage resistance threshold value R of In(3.0 mol%):Fe:Cu:LiNbO3 was 3.67×104 W/cm2 which was two orders of magnitude higher than that of Fe:Cu:LiNbO3 crystal (4.30×102 W/cm2). And the photo-damage resistance ability was enhanced by oxidized treatment. The In(2.0～3.0 mol%):Fe:Cu:LiNbO3 crystals with oxidized treatment have the best photorefractive properties.