Improvement of focused ultrasonic beam generated by laser phased array: Theoretical analysis

摘要

To improve the focused ultrasonic beam induced by laser phased array (LPA), the superiority of an improved LPA distribution with conjunction of geometric attenuation and directivity functions of the stimulated ultrasonic beams are investigated theoretically instead of only considering the directivity function. Numerical simulations for the generation of focused longitudinal waves in the thermoelastic regime were implemented to reveal the advantages of the improved LPA design. It is shown that the amplitude of the focused beam increased by 42.1%, and the rise time reduced by 25.0%, as well as spatial sizes narrowed by 50.6% and 41.9% in longitudinal and transverse directions, respectively. In addition, the thermal expansion superposition caused by adjacent laser pulses, which deteriorates the focusing features of the focused beam, should be avoided by setting proper spacing of LPA. Published under license by AIP Publishing.