High Q-factor monolithic optical microresonators found numerous applications in classical and quantum optical signal processing, microwave photonics, ultraprecise sensing, as well as fundamental optical and physical sciences. However, due to the solid structure of these microresonators, attaining the free spectral range tunability of most of them, critical for several of these applications, was, so far, unfeasible. To address this problem, here we experimentally demonstrate that the side-coupling of coplanar bent optical fibres can induce a high Q-factor whispering gallery mode optical microresonator. By changing the curvature radius of fibres from the centimetre order to the millimetre order, we demonstrate fully mechanically reconfigurable optical microresonators with dimensions varying from the millimetre order to 100-micron order and free spectral range varying from a picometre to ten picometre order. The developed theory describes the formation of the discovered microresonators and their major properties in a reasonable agreement with the experimental data. The new microresonators may find applications in cavity QED, microresonator optomechanics, frequency comb generation with tuneable repetition rate, tuneable lasing, and tuneable processing and delay of optical pulses.

高品质因数单片光学微谐振器在经典和量子光学信号处理、微波光子学、超精密传感以及基础光学和物理科学领域有着广泛的应用。然而，由于这些微谐振器的固体结构，迄今为止，实现其中大多数应用的自由光谱范围可调性（对于其中一些应用至关重要）是不可行的。为了解决这个问题，我们在这里通过实验证明，共面弯曲光纤的侧面耦合可以诱导高 Q 因子回音壁模式光学微谐振器。通过将光纤的曲率半径从厘米级改变到毫米级，我们展示了完全机械可重构的光学微谐振器，其尺寸从毫米级到100微米级不等，自由光谱范围从皮米级到十皮米级不等。所发展的理论描述了所发现的微谐振器的形成及其主要特性，与实验数据合理一致。新的微谐振器可以在腔 QED、微谐振器光机械、具有可调谐重复率的频率梳生成、可调谐激光以及光脉冲的可调谐处理和延迟中找到应用。