High-resolution imaging of ultrasonic fields through a multimode optical fiber

High-resolution ultrasound and photoacoustic imaging with flexible, lightweight probes is highly desirable for applications ranging from handheld clinical diagnostics to minimally invasive endoscopy and industrial inspection in confined environments. Piezoelectric transducer arrays, while widely used, face limitations in resolution, bandwidth, and scalability. To overcome these limitations, we present an approach that combines optical ultrasound detection using a Fabry-Pérot ultrasound sensor (FPUS) with light delivery through a single multimode optical fiber (MMF), utilizing wavefront shaping for beam control. This approach offers the capability to combine high-resolution imaging, a compact and flexible form factor, and software-defined reconfigurable array read-out. We present a prototype imaging system in which an FPUS is interrogated through a 200-µm-core-diameter MMF supporting ∼2000 spatial light modes, and use this system to map the ultrasound fields produced by known transducers. We demonstrate high-resolution, high-sensitivity ultrasonic field mapping, paving the way to a new class of versatile handheld imaging devices and endoscopes in medicine and industry.