Enhancement of pupil-masked wavelength-scale gas-filled flat acoustic lens based on anomaly apodization effect

Abstract

[EN] In this letter, the improvement in focus by the use of a pupil mask produced in an acoustic mesoscale cuboid particle ¿lled with CO2 is reported. Thereby, the result shows that the pupil mask increases the sound intensity and also increases the resolution (or a reduction of the full width at half maximum, FWHM) in focus compared to the non-masked one. These results are important because they con¿rm the effect of abnormal amplitude apodization for a one-wavelength dimension acoustic lens and demonstrate that it is possible to improve sound focusing of a cuboid gas-¿lled lens with one wavelength dimension. This is the smallest size of an acoustic lens ever considered in this type of literature, with side dimensions of the cube equal to one wavelength and a diameter to focus ratio of 2.5, the sound ampli¿cation in focus is 5.4 dB at 4125 Hz, with the resolution near to the diffraction limit.