Frequency-doubling effect in acoustic reflection by a nonlinear, architected rotating-square metasurface

Area of Science:

• Acoustics
• Materials Science
• Metamaterials

Background:

• Linear metamaterials offer wave control via dispersion engineering.
• Managing nonlinearities in dynamic elastic systems presents significant challenges.
• New strategies are needed for modeling and designing nonlinear wave behavior.

Purpose of the Study:

• To propose a nonlinear elastic metasurface design for controlling acoustic wave reflection.
• To demonstrate the capability of converting fundamental wave energy into second harmonic waves.

Main Methods:

• Design of a metasurface using rotating squares and deformable ligaments.
• Application of the harmonic balance method for theoretical analysis.
• Confirmation of theoretical results via time-domain simulations.

Main Results:

• Achieved efficient conversion of fundamental wave energy to second harmonic waves (conversion coefficient ~0.8).
• Demonstrated a low reflection coefficient (<0.05) at the incoming fundamental frequency.
• Validated theoretical predictions with numerical simulations.

Conclusions:

• The proposed nonlinear acoustic metasurface effectively controls acoustic wave reflection.
• The design enables significant nonlinear wave tailoring and amplitude-dependent wave manipulation.
• This approach can be extended to a broader range of architected structures for advanced metasurface applications.