Generation of a tunable Bessel ultrasound field via laser induction and its imaging application

Bessel ultrasound fields theoretically offer a highly focused spot with infinite depth of focus, but practical aperture constraints limit their focal depth. Laser-induced ultrasound utilizes optical methods to extend focal depth and achieve highly focused points, offering a promising strategy for generating and modulating Bessel fields. Here, we propose a tunable ring-shaped optical beam to create and adjust Bessel ultrasound fields, enabling adaptability across varied applications. We integrate optical lenses, absorbing materials, and a single-element transducer into a compact probe for ultrasound imaging. By tuning the optical ring via lens movement, we achieved ultrasound imaging with a 9-30 mm depth range and 215 μm lateral resolution. Compared to traditional methods, this approach demonstrates superior imaging performance in phantom and <i>ex vivo</i> experiments. This study develops a tunable laser-induced Bessel ultrasound field and applies it to ultrasound imaging, showing great potential in biomedical imaging.