Disordered crystals are being presently developed to enlarge the fluorescence bandwidth of trivalent lanthanides incorporated for generation of ultrashort (femtosecond) laser pulses in mode-locked oscillators and amplifiers, but crystal disorder induces a reduction of thermal conductivity which hampers the uniform crystal cooling after growth, leading to internal stresses. This is particularly remarkable when using the Laser Floating Zone (LFZ) growth technique; thus so far laser operation has been obtained only for LFZ-grown crystals with high thermal conductivity (κ ≥ 10 W m⁻¹ °C⁻¹) but without disorder, i.e. YAG, Y₂O₃ or REVO₄. To overcome this limitation we present the LFZ growth of (Lu_0.351Gd_0.630Yb_0.019)₂SiO₅ and (Lu_0.307Gd_0.612Nd_0.081)₂SiO₅ refractory (melting point ≈ 1950 °C) oxyorthosilicate single-crystal rods with dimensions suitable for high power diode laser pumping, despite these crystals having medium/low thermal conductivity, κ < 4 W m⁻¹ °C⁻¹. Rods with ≈10 mm length and ≈1.75 mm diameter were grown in air under a CO₂ laser at 10 mm h⁻¹. X-ray diffraction analyses confirm the monoclinic C2/c structure of the obtained crystals. For the chosen ≈0.3Lu/0.7Gd ratio some of the crystals are transparent and free of macro-defects. The continuous wave laser performance of Yb³⁺ and Nd³⁺ incorporated ions is demonstrated under Ti-sapphire laser pumping in an astigmatism compensated Z-shaped optical cavity. The laser performance of these LFZ oxyorthosilicates is found to be comparable to that reported in Czochralski (Cz) grown crystals. The faster pulling rate (almost one order of magnitude larger for LFZ than for Cz), the high crystal composition purity, and the absence of crucible or atmosphere control make the LFZ technique a low cost alternative for the present needs of diode laser pumped mode-locked medium/high power laser oscillators.

中文翻译：

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掺Yb或Nd掺杂（Lu0.3Gd0.7）2SiO5氧正硅酸盐单晶棒的激光浮区生长

目前正在开发无序晶体，以扩大掺入三价镧系元素的荧光带宽，以在锁模振荡器和放大器中产生超短（飞秒）激光脉冲，但是晶体紊乱会导致热导率下降，从而阻碍生长后均匀的晶体冷却，导致内在压力。当使用激光浮动区（LFZ）生长技术时，这一点尤其明显。到目前为止，仅对具有高导热率（κ≥10 W m ^-1 °C ^-1）且无扰动的LFZ生长晶体（即YAG，Y ₂ O ₃或REVO ₄）获得了激光操作。为了克服这一限制，我们提出了（Lu _0.351 Gd _0.630 Yb _0.019）₂ SiO ₅和（Lu _0.307 Gd _0.612 Nd _0.081）₂ SiO ₅耐火材料（熔点≈1950°C）的正硅酸单晶棒的LFZ生长。尽管这些晶体具有中等/低导热率，但对于高功率二极管激光泵浦来说，κ <4 W m ^-1 °C ^-1。在空气中，在10 mm h ^-1的CO ₂激光下，生长出长约≈10mm且直径约≈1.75mm的棒。X射线衍射分析证实了所获得晶体的单斜C 2 / c结构。对于所选的≈0.3Lu/ 0.7Gd的比率，某些晶体是透明的，没有宏观缺陷。Yb ³⁺和Nd ³⁺的连续波激光性能在钛-蓝宝石激光泵浦下，在像散补偿的Z形光学腔中展示了结合的离子。发现这些LFZ羟基原硅酸盐的激光性能与Czochralski（Cz）生长晶体中报道的激光性能相当。更快的提拉速度（LFZ的拉速比Cz高近一个数量级），高的晶体组成纯度以及缺乏坩埚或气氛控制功能，使得LFZ技术成为当前二极管激光泵浦模式需求的低成本替代方案-锁定的中/高功率激光振荡器。