Air coupled acoustic aperiodic flat lens

A method of designing a broadband acoustic lens, the method comprising:

• generating a plurality of initial seed designs of the broadband acoustic lens, wherein each design of the plurality of initial seed designs includes:
• a plurality of concentric rings, wherein each concentric ring of the plurality of concentric rings has a ring width;
• a plurality of gaps, wherein each gap of the plurality of gaps has a spacing;
• the concentric rings being separated by a spacing corresponding to a gap of the plurality of gaps;
• the widths of the plurality of concentric rings and the spacings of the plurality of gaps being arranged such that the incident acoustic wave is focused to a spot within a sub-wavelength of the incident acoustic wave in air, and
• wherein the arrangement of the widths of the plurality of concentric rings and spacings of the plurality of gaps is aperiodic;
• selecting a design of the plurality of initial seed designs using a fitness function;
• generating a first parent design from the selected design;
• optimizing the first parent design to generate a second parent design by adjusting features of the first parent design selected from a group consisting of:
• number of rings of the plurality of concentric rings, widths of the rings of the plurality of concentric rings, spacings of the plurality of gaps, material properties of each ring of the plurality of concentric rings, and combinations thereof;
• mating the first and second parent designs to generate a plurality of offspring;
• evaluating each of the plurality of offspring to select a candidate solution;
• and
• in response to the candidate solution not meeting a stop criteria, setting the first parent as the candidate solution and repeating the optimizing, mating, and evaluating.