The enhancement of the photoacoustic generation efficiency based on fiber optic ultrasound phased array

This paper presents the design, fabrication, and characterization of a new fiber optic ultrasound phased array generator. This novel ultrasound phased array generator is based on photoacoustic (PA) and phased array principle for biomedical ultrasound imaging applications. The gold nanocomposite, which was used as a photoacoustic material to generate the ultrasound signal, was coated on the tip of optical fibers. Four fiber optic ultrasound generation elements with different fiber lengths (1, 5, 9, 13 m or 1, 5, 5, 1 m) were used to build the ultrasound phased array generator. The time delay of the acoustic signal between each generation element was introduced due to the difference in optical fiber length. A hydrophone was used as the acoustic signal receiver for this ultrasound phased array generator. In this paper, two tests conducted and their results were reported. The first test was the steering angle test, and the second was the focus test. In the steering angle test, the steering angle was 9.5 degrees, which matched with the theoretical result when the time delay between each optical fiber was 0.02 mu s. Moreover, in the focus test, it has been demonstrated that the reported ultrasound phased array generator was capable of focusing the ultrasound with the focal length of 1.2 mm. Due to the focusing, the efficiency of the PA generation was 6.5 times higher than the single fiber structure. This fiber optic ultrasound phased array generator is the first step of a continuous study which will result in a novel fiber optic ultrasound probe for ultrasonic imaging applications. (C) 2019 Elsevier Ltd. All rights reserved.