Silica optical microspheres often exhibit ultra-high quality factors, yet their group velocity dispersion, which is crucial for nonlinear optics applications, can only be coarsely tuned. We experimentally demonstrate that group-velocity dispersion of a silica microsphere can be engineered by coating it with conformal nanometric layers of alumina yet preserving its ultra-high optical quality factors (∼10⁷) at telecom wavelengths. Using the atomic layer deposition technique for the dielectric coating, which ensures nm-level thickness control, we not only achieve a fine dispersion tailoring but also maintain a low surface roughness and material absorption to ensure a low optical loss. Numerical simulations supporting our experimental results show that the alumina layer thickness is a promising technique for precise tuning of group-velocity dispersion. As an application, we demonstrate the generation of Kerr optical frequency combs, showing that the alumina coatings can also sustain the high optical intensities necessary for nonlinear optical phenomena.

中文翻译：

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用于超高Q微谐振器中分散管理的氧化铝涂层

二氧化硅光学微球通常表现出超高质量的因子，但是它们的群速度色散对于非线性光学应用至关重要，只能粗调。我们通过实验证明，可以通过在二氧化硅微球上涂覆保形纳米层氧化铝，同时保留其超高光学品质因数（〜10 ⁷）在电信波长下。使用用于介电涂层的原子层沉积技术确保纳米级的厚度控制，我们不仅实现了精细的色散调整，而且还保持了较低的表面粗糙度和材料吸收率，从而确保了较低的光学损耗。支持我们的实验结果的数值模拟表明，氧化铝层的厚度是一种用于精确调整群速度色散的有前途的技术。作为应用，我们演示了Kerr光学频率梳的产生，表明氧化铝涂层还可以维持非线性光学现象所需的高光学强度。