In this work, we present a thorough analysis on M-bonacci zone plates for ultrasound focusing applications. These planar lenses are capable of providing bifocal focusing profiles with equal intensity in both foci and become very appealing for a wide range of scenarios including medical and industrial applications. We show that in high-wavelength domains, such as acoustics or microwaves, the separation between both foci can be finely adjusted at the expense of slightly increasing the distortion of the focusing profile, and we introduce a design parameter to deal with this issue and simplify the design process of these lenses. Experimental measurements are in good agreement with numerical simulations and demonstrate the potential of M-bonacci lenses in ultrasound focusing applications.
Keywords: Fresnel zone plate; M-bonacci zone plate; acoustic focusing; acoustic lens.