Optical fibers play a key role in many different fields of science and technology. In particular, fibers with a diameter of several micrometers are intensively used in photonics. For these applications, it is often important to precisely know and control the fiber radius. Here we describe a technique to determine the radius profile of an optical microstructure with ultrahigh precision from a single optical image. Using a basic microscopy setup, we demonstrate our method by measuring the axial radius variation along a 30-$\mu \mathrm{m}$-diameter silica fiber with precision less than 0.3 Å. The axial resolution is tens of micrometers, and the measurement range is more than 0.5 mm. Our method relies on imaging the fiber’s whispering-gallery modes in which the speed of light propagating along the fiber axis is strongly reduced. Imaging those whispering-gallery modes, we infer the local radius variations of the optical microstructure with ultrahigh precision. Because of the performance and simplicity of implementation, we are convinced that our scheme has high potential for precision metrology and optical sensing.

中文翻译：

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具有亚埃级精度的微纤维半径变化的慢光增强光学成像

光纤在科学和技术的许多不同领域中起着关键作用。特别地，直径为几微米的纤维被广泛用于光子学中。对于这些应用，精确了解和控制光纤半径通常很重要。在这里，我们描述了一种从单个光学图像以超高精度确定光学微结构的半径轮廓的技术。使用基本的显微镜设置，我们通过测量沿30-$\mu \mathrm{米}$直径小于0.3Å的石英纤维。轴向分辨率为数十微米，测量范围大于0.5毫米。我们的方法依赖于对光纤的回音壁模式进行成像，在这种模式下，沿光纤轴传播的光速会大大降低。成像那些耳语的画廊模式，我们以超高精度推断光学微结构的局部半径变化。由于执行的性能和简单性，我们相信我们的方案在精密计量和光学传感方面具有很高的潜力。