Microbubble resonators combined with a digital optical frequency comb for high-precision air-coupled

• 作 者: JingshunPan BinZhang ZhengyongLiu JiaxinZhao YuanhuaFeng LeiWan ZhaohuiLi
• 机 构: KeyLaboratoryofOptoelectronicMaterialsandTechnologies,SchoolofElectricalandInformationTechnology,Sun
• 出 处: PhotonicsResearch
• 发表日期: 2020年8期

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 $4.4\mathrm{mPa}/\surd \mathrm{Hz}$ is achieved by combining a high-$Q$ ($～3\times {10}^7$) 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.