Multipoint Laser-Ultrasonic Excitation Transducer Using Multimode Fiber

Abstract

Opto-acoustic excitation is a promising alternative to conventional electro-acoustic methods, with significant potential in non-destructive testing and medical imaging. We propose and demonstrate a multipoint laser-ultrasonic excitation transducer system in this study, which is formed by fusing a multimode fiber segment with single-mode fibers at both ends. Both theoretical simulations and experimental results indicate a close correlation between the coupling coefficient of a transducer and the length of the multimode fiber. The transducer structure is easy to manufacture, and a four-point energy-balanced ultrasound excitation transducer system has been achieved in a simple and cost-effective manner, by connecting transducers with different coupling coefficients in increasing order. Furthermore, this type of optical fiber ultrasonic transducer exhibits an elevated energy conversion efficiency, relatively high SNR and a flat spectrum, and can effectively address the limitations of traditional piezoelectric ceramics, such as susceptibility to electromagnetic interference, narrow frequency response range, complex installation and connection processes, and a relatively large size. It is expected to have a significant impact on structural health monitoring for buildings and deep tissue imaging in biomedical applications.

Keywords: Fiber-optic, photoacoustic imaging, structural health-monitoring, Ultrasonic Transducer