Second-order nonlinear mixing processes involving a leaky guided acoustic wave.

Area of Science:

• Acoustics
• Nonlinear Wave Phenomena
• Solid Mechanics

Background:

• Nonlinear acoustic wave mixing is crucial for advanced wave manipulation.
• Quantifying nonlinear acoustic processes requires accurate parameters like the acoustic nonlinearity parameter (ANP).

Purpose of the Study:

• To analyze quasi-phasematched mixing of acoustic waves using second-order nonlinearity.
• To develop and compare two approximate methods for estimating the ANP in guided wave systems.

Main Methods:

• Perturbation theory to derive a stationary solution for the displacement field.
• Resonant state expansion to express the ANP as an overlap integral.
• Application of finite element calculations for validation.

Main Results:

• Two distinct methods for ANP estimation were proposed and analyzed.
• Both methods showed good agreement for localized leaky output waves.
• The first method was successfully applied to nonlinear mixing of edge waves in elastic plates.

Conclusions:

• The developed methods provide accurate estimations of the acoustic nonlinearity parameter.
• These findings are applicable to understanding and designing nonlinear acoustic devices.
• The study validates the utility of perturbation theory and resonant state expansion in nonlinear acoustics.