Consistency Evaluation on Preparation Methods of Optical Fiber Photoacoustic Probe

High consistency of optical fiber photoacoustic (PA) probe contributes to the favorable comparability and reliability of ultrasound testing for biomedical imaging and industrial nondestructive detection. Other than traditional dip coating method, direct spin coating or spin coating- transfer methods are used to fabricate miniature optical fiber PA probes whose endfaces are coated with carbon black/PDMS or nano-carbon powder/PDMS composite. Then the coefficient of variation (CV) is proposed to evaluate the consistency of the developed PA probes in terms of ultrasound pressure, energy conversion efficiency, average frequency and bandwidth. Ultrasound test in a water tank shows that the PA probe with 1% mass fraction of nano carbon powder mixed with PDMS via spin coating-transfer method exhibits a higher consistency with the CV values of 32.0%, 11.8%, 3.1 % and 11.7% corresponding to the aforementioned four consistency parameters. The presented evaluation scheme can also be extended for other types of PA probes using 2D photothermal materials.