Fourier Acoustical Tweezers: Synthesizing Arbitrary Radiation Force Using Nonmonochromatic Waves on Discrete-Frequency Basis

Existing acoustical tweezers (ATs) modulate source geometries to achieve monochromatic focusing, the wide frequency space allowed by sources is neglected. Here an analogous approach is proposed to synthesize AT fields in temporal frequency instead of wave vector. The base element is a standing wave, its counterpart in beam ATs is the field of a pitch. After field periodization, radiation-force theory is extended to nonmonochromatic waves having arbitrary in-period force based on discrete-frequency Fourier analysis. Fourier acoustical tweezers (FATs) achieve a minimal spacing of $\ensuremath{\lambda}/4$ for independent trapping. System complexity is reduced to two sources per dimension.