Fast and sensitive air-coupled ultrasound detection is essential for many applications such as radar, ultrasound imaging, and defect detection. Here we present a novel approach based on a digital optical frequency comb (DOFC) technique combined with high-Q optical microbubble resonators (MBRs). DOFC enables precise spectroscopy on resonators that can trace the ultrasound pressure with its resonant frequency shift with femtometer resolution and sub-microsecond response time. The noise equivalent pressure of air-coupled ultrasound as low as 4.4 mPa/√Hz is achieved by combining a high-Q (∼3×107) MBR with the DOFC method. Moreover, it can observe multi-resonance peaks from multiple MBRs to directly monitor the precise spatial location of the ultrasonic source. This approach has a potential to be applied in 3D air-coupled photoacoustic and ultrasonic imaging.

中文翻译：

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用于高精度空气耦合超声检测器的微泡谐振器结合数字光频梳

快速而灵敏的空气耦合超声检测对于雷达、超声成像和缺陷检测等许多应用至关重要。在这里，我们提出了一种基于数字光频梳 (DOFC) 技术与高 Q 光学微泡谐振器 (MBR) 相结合的新方法。DOFC 能够在谐振器上实现精确的光谱分析，这些谐振器可以通过其谐振频移、飞米分辨率和亚微秒响应时间来追踪超声压力。通过将高 Q (∼3×107) MBR 与 DOFC 方法相结合，可实现低至 4.4 mPa/√Hz 的空气耦合超声的噪声等效压力。此外，它可以观察来自多个 MBR 的多共振峰，直接监测超声源的精确空间位置。