Fiber-optic laser-ultrasound generation on a fiber side wall based on peanut-shape structure

Ultrasonic nondestructive testing plays a more and more important role in modern production and construction. In this paper, a novel ultrasonic energy transfer technique based on peanut shape structure is proposed and demonstrated. The ultrasonic device is able to effectively couple the laser energy in the fiber core to the cladding of the single-mode fiber (SMF) by using the micro machined fiber structure. The laser energy coupled to the cladding can be absorbed by the ultrasonic conversion material coated on the surface of the SMF. Due to the ultrasonic conversion material has high thermal elastic coefficient, it can produce mechanical expansion and contraction process after absorbing the laser, resulting in the generation of the ultrasonic signal. The ultrasonic transducer based on peanut shape taper only needs to be fused by SMF and fiber splicer. The proposed laser-ultrasonic transducer has many advantages, such as simple preparation, cost-effective, and high energy conversion efficiency. Such characteristics makes the proposed laser-ultrasonic transducer attractive for practical applications.