Float zone growth of rare-earth doped lutetium orthovanadate single crystals as new solid state laser materials

新型固态激光材料稀土掺杂原钒酸镥单晶的浮区生长

• 批准号: 15550169
• 负责人: HIGUCHI Mikio
• 金额: $ 2.5万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15550169/
• 关键词: Floating zone method; Lutetium orthovanadate; Single crystal; Solid state laser; Rare-earth doping; Laser-diode pumping; 固体レーザ材料

Neodymium-doped lutetium orthovanadate (Nd : LuVO_4) has larger absorption and emission cross sections as compared with conventional Nd-doped rare earth orthovanadates and is expected to be applied for laser-diode pumped solid state lasers. LuVO_4 is also expected to be a good host crystal for Tm and Yb, since the tonic radius of Lu^<3+> is comparable to those of Tm^<3+> and Yb^<3+>. In this study, the growth technique of rare-earth (Nd, Tm and Yb) doped LuVO_4 single crystals by the floating zone technique has been established and some spectroscopic properties as a laser material have been investigated.Each dopant was added with 0.5-4 at% with respect to Lu. Growth conditions were as follows : traveling rate of the molten zone was 20-40 mm/h ; rotation rate was 30-40 rpm ; direction was [110] and atmosphere was an oxygen flow Any as-grown crystal was colored in yellowish ocher, but the coloring was completely eliminated by annealing at 1000 ℃ for 20h in air. Polarizing microscopy proved that the grown crystals contained no macroscopic defects but growth striations were observed only in Nd-doped crystals. Effective segregation efficient was determined to be close to unity for Tm and Yb and about 0.5 for Nd. At this stage, single crystals 5 mm in diameter and 50 mm long have been grown reproducibly for Tm-and Yb-doping of up to 5 at% and Nd-doping of up to 1 at%.The absorption coefficient of Nd : LuVO_4 was 1.4 times as high as those of other rare-earth orthovanadates. The Nd : LuVO_4 (1 at%) single crystal exhibited excellent laser performance with 880 nm pumping ; that is, the slope efficiency was 73 % and the threshold was 7 mW. Although the laser oscillation experiments for Tm and Yb-doped crystals are underway, it is expected that those crystals also exhibit good laser performance on the basis of their excellent spectroscopic properties.

掺Nd3+的正钒酸锶(ND：LuVO4)与传统的掺稀土正钒酸锶相比，具有更大的吸收截面和发射截面，有望应用于激光二极管泵浦的固体激光器。LuVO_4也有望成为Tm和Yb的良好基质晶体，因为Lu^&lt；3+&gt；的声子半径与Tm^&lt；3+&gt；和Yb^&lt；3+&gt；相当。本研究建立了用浮区法生长稀土(Nd、Tm、Yb)掺杂的LuVO_4单晶的工艺，并研究了作为激光材料的一些光谱性质。生长条件为：熔区移动速度为20~40 mm/h，旋转速度为30~40rpm，晶向为[110]，气氛为氧气流动，生长的晶体呈微黄色，在空气中1000℃保温20h可完全消除。偏光显微镜证明生长的晶体不含宏观缺陷，但只在掺钕晶体中观察到生长条纹。Tm和Yb的有效偏析系数接近1，而ND的有效偏析系数约为0.5。在这个阶段，当Tm和Yb的掺杂量达到5at%，Nd的掺杂量达到1at%时，可以重复生长出直径5 mm，长50 mm的单晶，其吸收系数是其他稀土原钒酸盐的1.4倍。在880 nm的泵浦下，Nd：LuVO4(1at%)晶体表现出优良的激光性能，即斜率效率为73%，阈值为7 mW。虽然Tm和Yb掺杂晶体的激光振荡实验仍在进行中，但由于它们具有优异的光谱特性，人们期望它们也能表现出良好的激光性能。