Depressed-index buried and surface channel waveguides (type III) are produced in a bulk 3.5 at.% Tm3+:CALGO crystal by femtosecond direct-laser-writing at kHz repetition rate. The waveguides are characterized by confocal microscopy and µ-Raman spectroscopy. Under in-band-pumping at 1679 nm (3H6 → 3F4 transition) by a Raman fiber laser, the buried channel waveguide laser with a circular cladding (diameter: 60 µm) generated a continuous-wave output power of 0.81 W at 1866-1947 nm with a slope efficiency of 71.2% (versus the absorbed pump power) and showed a laser threshold of 200 mW. The waveguide propagation losses were as low as 0.3 ± 0.2 dB/cm. The laser performance under in-band pumping was superior compared pumping at ∼800 nm (3H6 → 3H4 transition), i.e., the convetional pump wavelength. Vibronic laser emission from the WG laser above 2 µm is also achieved. The low-loss behavior, the broadband emission properties and good power scaling capabilities indicate the suitability of Tm3+:CALGO waveguides for mode-locked laser operation at ∼2 µm.

中文翻译：

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Tm：CALGO中的超快激光内接波导激光器，带有下折射率包层。

通过飞秒直接激光写入，以kHz重复频率，在体积为3.5 at。％的Tm3 +：CALGO晶体中生产了折射率降低的埋入式和表面沟道波导（III型）。波导的特征在于共聚焦显微镜和拉曼光谱。在拉曼光纤激光器在1679 nm的带内泵浦（3H6→3F4跃迁）下，带有圆形包层（直径：60 µm）的掩埋通道波导激光器在1866-1947年产生了0.81 W的连续波输出功率效率为71.2％（相对于吸收的泵浦功率）的光通量为100 nm，激光阈值为200 mW。波导传播损耗低至0.3±0.2 dB / cm。带内泵浦下的激光性能优于在〜800 nm（3H6→3H4跃迁）即对流泵浦波长下的泵浦性能。还可以实现WG激光器发出的2微米以上的振动激光。低损耗性能，宽带发射特性和良好的功率缩放能力表明Tm3 +：CALGO波导适用于约2 µm的锁模激光工作。