Marques Dylan M, Sheppard Oliver, Zhang Edward Z, Munro Peter R T, Guggenheim James A
Appl Opt. 2025 Apr 1;64(10):2366-2373. doi: 10.1364/AO.548048.
Fabry-Perot (FP) ultrasound sensors are a class of optical ultrasound sensors used in photoacoustic tomography (PAT) and other applications. Conventionally, an FP ultrasound sensor comprises an ultrasonically compressible planar microcavity, locally interrogated by a focused Gaussian beam. One way to increase the sensitivity could be to replace this beam with a Bessel beam. The rationale is twofold. First, as a Bessel beam's wavefront better matches the modes of the planar microcavity, this could increase the -factor, leading to higher sensitivity. Second, as a Bessel beam provides a focused spatial structure-a central core surrounded by concentric rings-it might retain the ability to locally interrogate the sensor. To explore this idea, we developed an experimental system featuring a custom FP ultrasound sensor interrogated by a Bessel beam and evaluated its on-axis sensitivity, directivity, and image resolution when performing PAT. For comparison, we measured the same characteristics using a conventional focused Gaussian beam with a spot size similar to the core of the Bessel beam. As anticipated, the Bessel beam provided a higher ultrasonic on-axis sensitivity. However, the directivity and spatial resolution were degraded, suggesting that the Bessel beam yielded a larger acoustic element. We conclude that it is feasible to increase the sensitivity of an FP ultrasound sensor using a Bessel beam. Further work is required to establish whether differently designed Bessel beams could concurrently offer a smaller acoustic element.
法布里-珀罗（FP）超声传感器是一类用于光声断层扫描（PAT）及其他应用的光学超声传感器。传统上，FP超声传感器包括一个可超声压缩的平面微腔，由聚焦高斯光束进行局部探测。提高灵敏度的一种方法可能是用贝塞尔光束取代该光束。其理由有两方面。首先，由于贝塞尔光束的波前与平面微腔的模式更好匹配，这可能会增加品质因数，从而提高灵敏度。其次，由于贝塞尔光束提供了一种聚焦的空间结构——一个被同心环包围的中心核心——它可能保留局部探测传感器的能力。为了探究这一想法，我们开发了一个实验系统，该系统具有一个由贝塞尔光束探测的定制FP超声传感器，并在执行PAT时评估了其轴向灵敏度、方向性和图像分辨率。为作比较，我们使用光斑尺寸与贝塞尔光束核心相似的传统聚焦高斯光束测量了相同的特性。正如预期的那样，贝塞尔光束提供了更高的超声轴向灵敏度。然而，方向性和空间分辨率有所下降，这表明贝塞尔光束产生了一个更大的声学元件。我们得出结论，使用贝塞尔光束提高FP超声传感器的灵敏度是可行的。需要进一步开展工作来确定不同设计的贝塞尔光束是否能同时提供一个更小的声学元件。
