摘要
1.5~1.7μm人眼安全波段激光在激光测距、激光雷达和光通信等领域具有重要应用。然而,现有的Er:YAG、Er:LuYO3等激光晶体受限于较小的发射截面或晶体尺寸,难以满足高功率、大型化激光器的需求。因此,开发兼具大尺寸和高发射截面的新型激光晶体已成为当前研究的热点。本工作采用冷坩埚法生长了稀土掺杂钇稳定氧化锆(YSZ)晶体,晶体呈<111>择优生长取向,单体直径和长度都超过150 mm(6英寸),是目前所知最大的YSZ单晶。研究了Er掺杂YSZ晶体的吸收、发射光谱。结果表明,在971 nm波长激发下,YSZ:Er晶体在1530 nm处表现出强发射峰,对应^(4)I_(13/2)→^(4)F_(15/2)跃迁;发射截面随Er^(3+)含量变化,Er^(3+)含量为1.60%(摩尔分数,下同)时为4.811×10^(-20)cm^(2);荧光寿命随着Er^(3+)含量增加逐渐减小,Er^(3+)含量为1.60%时荧光寿命为1.149 ms。通过掺杂离子和掺杂浓度的优化,YSZ:Er晶体有望成为一种潜在的激光晶体材料。
Introduction Lasers operating within a spectral range of 1.5-1.7μm are essential for eye-safe applications like laser ranging,lidar,and optical communications,etc..Nevertheless,conventional laser crystals such as Er:YAG and Er:LuYO3 have limitations in emission cross-sections or attainable crystal dimensions,thereby constraining their utilization in high-power,large-scale laser systems.To address these challenges,the development of novel laser crystals with substantial crystal sizes and high emission cross-sections is thus imperative.Yttria-stabilized zirconia(YSZ)doped with rare-earth ions emerges as a promising candidate due to its disordered crystalline structure that enables a broader wavelength tunability and a reduced thermal loading under resonant pumping conditions.Specifically,erbium(Er^(3+))doped YSZ crystals have a significant potential due to its intense emission at 1.5μm(^(4)I_(13/2)→^(4)F_(15/2) transition)for eye-safe laser.This study was to investigate the growth of large-scale Er^(3+)-doped YSZ crystals by a skull melting technique,and the optical and spectral properties were systematically investigated to explore a novel laser gain medium in the infra-red region.Methods Pure YSZ and Er^(3+)-doped YSZ crystals(i.e.,0.36%,1.60%and 2.54%in mole)were grown by a skull melting method(or a cold crucible technique),and a radio frequency(RF)generator was used to heat up the charges.A large-scale furnace with a diameter of approximately 150 cm was employed to accommodate the spontaneous nucleation.Graphite electrodes were used for initial arcing due to the poor conductivity of ZrO_(2) at<1200℃.At>1200℃,raw materials became an electric conductor to form the melting pool.The lowering mechanism started to work at a lowering rate of 2 mm/h,and the melt crystallized from the bottom to the top.After the growth,annealing process was performed to release the internal stresses.The phase and crystal structures of as-grown crystals were characterized by X-ray diffraction(XRD).The transmittance and absorption properties were analyzed by UV-Vis-NIR spectroscopy.The luminescence and decay curve were also systematically evaluated.Results and Discussion The results show that Large-sized YSZ and Er-doped YSZ crystals with the diameters and lengths of exceeding 150 mm(6 inches)are grown,representing the largest YSZ single crystals reported.The XRD patterns indicate the cubic structure with a preferred<111>preferred orientation.The lattice parameters increase slightly with Er^(3+)concentration,indicating the effective incorporation of Er^(3+)into the YSZ lattice.The transmission of exceeding 74%in the range of 400-1650 nm occurs for pure YSZ crystals,confirming relatively high crystalline qualities.The absorption spectra for Er-doped crystals show some characteristic peaks at 378,408,451,489,518,546,654,971,1460 nm and 1530 nm,corresponding to Er^(3+)transitions from the ground state ^(4)F_(15/2) to excited states such as 4G11/2 and 4F11/2.The most intense absorption band occurs at 971 nm,which is attributed to the ^(4)F_(15/2)→4F11/2 transition.Under 971 nm excitation,the emission spectra exhibit a dominant peak at 1530 nm for the ^(4)I_(13/2)→^(4)F_(15/2) transition,which is ideal for eye-safe lasers.The great emission intensity appears at an Er^(3+)mole concentration of 1.60%,with an emission cross-section of 4.811×10^(-20) cm^(2),which is significantly higher than that of Er:YAG(i.e.,0.6×10^(-20) cm^(2))and Er:LuYO3(i.e.,0.261×10^(-20) cm^(2)).Correspondingly,the decay time of YSZ:0.36,YSZ:1.60and YSZ:2.54 crystals is 1.836 ms,1.149 ms and 0.797 ms,respectively.Conclusions This study demonstrated the effective growth of large-scale(6-inch)YSZ and Er-doped YSZ crystals by a skull melting method.YSZ:Er crystals exhibited an intense emission at 1530 nm under 971 nm excitation.In particular,a high emission cross-section of 4.811×10^(-20) cm^(2) and suitable fluorescence lifetime of 1.149 ms appeared for Er^(3+)of 1.60%in mole.YSZ:Er crystals could be used as a highly promising gain medium for high-power,eye-safe lasers at 1.5μm due to the ultra-large crystal size and relatively large emission cross-section.
作者
陈宇轩
蒋新
申慧
田甜
蒋泽锋
徐家跃
CHEN Yuxuan;JIANG Xin;SHEN Hui;TIAN Tian;JIANG Zefeng;XU Jiayue(School of Materials Science and Engineering,Shanghai Institute of Technology,Shanghai 201418,China;Guangxi Guilin Jiaxing Crystal Gem Co.,Ltd,Guilin 542501,China;Sicuan Chengdu Xinxing Crystal Gemstone Co.,Ltd,Chengdu 610000,China)
出处
《硅酸盐学报》
北大核心
2025年第12期3476-3483,共8页
Journal of The Chinese Ceramic Society
基金
国家自然科学基金(51572175)。
关键词
钇稳定立方氧化锆
冷坩埚法
晶体生长
激光晶体
yttria-stabilized zirconia
skull melting method
crystal growth
laser crystal
