Interrogation of Fabry-Pérot ultrasound sensors with Bessel beams

Fabry-Perot etalon-based ultrasound detectors are typically interrogated with a focused Gaussian beam in order to achieve a desired acoustic element size. However, tightly focused Gaussian beams lead to beam †walk-off' within the etalon cavity which reduces sensitivity. In previous work, the planar geometry of the Fabry-Perot etalon has been replaced by a curved geometry matched to the interrogation beam geometry, thus preventing walk-off. In this work we instead propose using propagation invariant Bessel beams, thus matching the beam geometry to that of the planar etalon geometry, to reduce beam walk-off and increase sensitivity. Increased sensitivity may extend the imaging depth of Fabry-Perot ultrasound detection systems and may thus enable photoacoustic imaging to access a range of deep tissue imaging applications.