| Ultrasound detection and imaging technologies are widely used in non-destructive testing (NDT) and medical diagnostic applications. In most applications, the ultrasound generators are required to possess broadband, compact size, and high efficiency. As an attractive alternative to the traditional piezoelectric ultrasound generators, fiber-optic ultrasound generators based on photoacoustic principle are promising to overcome challenges brought by those ultrasound applications.;The basic idea of the photoacoustic generation is to convert pulsed-optical irradiation energy into heat which then generates acoustic waves by thermal expansion. This working mechanism makes it an inherently broadband ultrasound generation method due to the development of the ultra-fast laser. In addition, as compact waveguides (typically 125 mum in diameter), optical fibers are excellent carriers for miniaturized photoacoustic ultrasound generators. What is more, the mixture of nanostructures and polymer has been found to be an efficient photoabsorptive material. Therefore, the successful completion of this dissertation provides guidelines to design and fabricate photoacoustic generators with broadband, compact size, and high efficiency.;The photoabsorptive layer coated on the fiber endface plays an important role in converting the laser energy into heat and exciting the acoustic wave. The selection of the photoabsorptive materials and the optimization of the structure dimension are keys for achieving high energy-conversion efficiency. Periodic metallic nanostructures are promising energy-absorption materials due to their high concentration and the capability of optical energy absorption at plasmon resonance frequency.;In this dissertation, numerical simulations including finite element analysis (FEA) and finite integral technique (FIT) are efficient ways to provide practical clues for the design and fabrication of the fiber-optic ultrasound generator. The focused ion beam (FIB) can be used as a promising nano-scale milling tool on the fiber endface for fabrication of the periodic metallic nanostructures. The fabricated fiber-optic devices are demonstrated to generate ultrasound. All the results and future works are discussed. This research could open up a new avenue for research on highly efficient all optical fiber ultrasound transducers. |
