Ultrasound detection and imaging technologies have been widely used in nondestructive and non-invasive testing applications in industry and medical areas. Ultrasonic transducers are key elements in these applications. In many advanced applications, such as high resolution medical imaging, requirements for novel ultrasonic transducers featuring wide bandwidth, high frequency and compact size are rising. Piezoelectric ultrasonic transducers, which are broadly used in various ultrasound applications nowadays, are being challenged by these requirements. In order to address these requirements, photoacoustic technology has been studied for years to overcome challenges brought by the most advanced ultrasound applications.;Photoacoustics, also called as optoacoustics, is a technology that generates acoustic signals through an optical approach. The energy from the optical radiation converts into the heat which causes the optical excited material to expand due to the thermal expansion phenomenon. Therefore, mechanical waves which are also acoustic waves are generated. The principle of the photoacoustic makes it an inherently wide bandwidth ultrasound generation method due to the development of the ultra fast laser. Taking advantage of the ultra fast laser, the ultrasound transducers based on the photoacoustic principle can potentially have wide bandwidth.;Another challenge brought by modem ultrasound detection applications, high spatial resolution, can be solved by optical fibers. Featuring a compact size (generally 125 gm in diameter), optical fibers are excellent carriers for miniature photoacoustic ultrasonic transducers. The spatial resolution can be enhanced due to the compact size of the optical fiber. Due to the compact size of the optical fiber and their wide bandwidth from the photoacoustic principle, an ultrasound transducer featuring wide bandwidth and high spatial resolution can be achieved.;The goal of this thesis is to develop a fiber optic photoacoustic ultrasound transducer that can generate and detect ultrasound signals simultaneously. This thesis will separate the study into several small projects and provide a detailed description of each project. Firstly, as a primary function and physical carrier, a fiber optic ultrasound receiver was fabricated and characterized. Secondly, two types of photoacoustic generation materials were synthesized and studied for the purpose of the photoacoustic generation efficiency enhancement. The generation efficiency was increased 3 orders of magnitude comparing to the thin aluminum film. Thirdly, fiber optic ultrasound generators were studied by applying both materials. Finally, the integration of the ultrasound generation and detection functions was realized by two configurations. This thesis firstly reported a fiber optic ultrasound transducer which integrates the ultrasound generation and detection functions on a single optical fiber. And the fiber optic ultrasound transducer can generate and detect ultrasound signals simultaneously. The study results of this thesis will benefit the material and the transducer community.
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