Thermoacoustic-reflected focusing lens based on acoustic Bessel-like beam with phase manipulation**Project supported by the National Natural Science Foundation of China (Grant Nos. 11774137 and 51779107), the Six-Talent Peaks Project in Jiangsu Province, China (Grant No. GDZB-019), the China Postdoctoral Science Foundation (Grant No. 2017M621643), the Natural Science Foundation of Jiangsu Higher Educational Institutions of China (Grant No. 18KJB140003), and the

Abstract

We report the realization of broadband reflected acoustic focusing lenses based on thermoacoustic phased arrays of Bessel-like beams, in which the units of phase manipulation are composed of three rigid insulated boundaries and a thermal insulation film in air with different temperatures. Based on these units, we realize a reflected focusing lens which can focus reflected acoustic energy on a line, and its fractional bandwidth can reach about 0.29. In addition, we discuss the influences of the base angle of Bessel-like beam, the number of basic unit, and the variation of unit temperature on focusing performances in details. Furthermore, the reflected focusing lens for the cylindrical acoustic wave based on the Bessel-like beam is also demonstrated. The proposed focusing lens has the advantages of a broad working bandwidth, large focus size, and high robustness, which may provide possibilities for the design and application of acoustic lenses.