Frequency distillation with dispersive reflector for multitone ultrasound perception

Frequency separation plays a key role in both information science and device applications such as sensors, filters, and multiplexers. However, rather than the readily-available optical spectral separation benefiting from the intrinsic dispersion of natural materials, frequency separation in acoustics is challenging due to the negligible dispersion in natural materials over a wide frequency range, yet it is imperative for acoustic signal processing and biomedical science. Here, we numerically design and experimentally realize the frequency separation and perception for underwater multitone ultrasound or dubbed frequency distillation in our work. It is achieved by a dispersive reflector, which spatially splits the ultrasound waves of different frequencies superimposed in the incident beam into different reflection directions. The precise frequency distillation with strong robustness is validated by the evidence of high distilled accuracy rate (over 95%), highly distinguishable spectral resolution (within 5%), and broad effective frequency range (over 0.85 octaves), even in the presence of defects or alterations in the configuration. Moreover, compared to the previous spectral separation devices based on rainbow trapping where the sound is localized inside the specific positions of the structure, our scheme allows the distilled wave propagating outside, which facilitates the post-processing of signals. These pronounced properties of the underwater ultrasound dispersive reflector for frequency distillation and perception are promising for the integrated and chip-scale devices in acoustic communication, signal processing, and biomedical sensing and imaging.