La Tai Anh, Ülgen Okan, Shnaiderman Rami, Ntziachristos Vasilis
Institute of Biological and Medical Imaging, Helmholtz Zentrum München, Neuherberg, Germany.
Chair of Biological Imaging at the Central Institute for Translational Cancer Research (TranslaTUM), School of Medicine and Health, Technical University of Munich, Munich, Germany.
Nat Commun. 2024 Aug 30;15(1):7521. doi: 10.1038/s41467-024-51497-1.
Fiber-based interferometers receive significant interest as they lead to miniaturization of optoacoustic and ultrasound detectors without the quadratic loss of sensitivity common to piezoelectric elements. Nevertheless, in contrast to piezoelectric crystals, current fiber-based ultrasound detectors operate with narrow ultrasound bandwidth which limits the application range and spatial resolution achieved in imaging implementations. We port the concept of silicon waveguide etalon detection to optical fibers using a sub-acoustic reflection terminator to a Bragg grating embedded etalon resonator (EER), uniquely implementing direct and forward-looking access to incoming ultrasound waves. Precise fabrication of the terminator is achieved by continuously recording the EER spectrum during polishing and fitting the spectra to a theoretically calculated spectrum for the selected thickness. Characterization of the EER inventive design reveals a small aperture (10.1 µm) and an ultra-wide bandwidth (160 MHz) that outperforms other fiber resonators and enables an active detection area and overall form factor that is smaller by more than an order of magnitude over designs based on piezoelectric transducers. We discuss how the EER paves the way for the most adept fiber-based miniaturized sound detection today, circumventing the limitations of currently available designs.
基于光纤的干涉仪备受关注，因为它们能够实现光声和超声探测器的小型化，且不会出现压电元件常见的灵敏度二次损失。然而，与压电晶体不同的是，当前基于光纤的超声探测器在窄超声带宽下工作，这限制了成像应用中的应用范围和空间分辨率。我们将硅波导标准具检测的概念移植到光纤中，使用亚声反射终端连接到布拉格光栅嵌入式标准具谐振器（EER），独特地实现了对入射超声波的直接和前瞻性访问。通过在抛光过程中连续记录EER光谱并将光谱拟合到所选厚度的理论计算光谱，实现了终端的精确制造。对EER创新设计的表征显示，其具有小孔径（10.1 µm）和超宽带宽（160 MHz），优于其他光纤谐振器，并且与基于压电换能器的设计相比，其有效检测面积和整体外形尺寸小一个多数量级。我们讨论了EER如何为当今最先进的基于光纤的小型化声音检测铺平道路，规避了现有设计的局限性。
