Time reversed wave propagation experiments in chaotic micro-structured cavities

Area of Science:

• Solid-state physics
• Acoustics
• Materials science

Background:

• Elastic wave propagation in solids is fundamental to many physical phenomena.
• Micro-patterned structures can significantly alter wave behavior through scattering and dispersion.
• Time reversal and reciprocity are key symmetries in wave physics.

Purpose of the Study:

• To experimentally investigate elastic wave propagation in strongly scattering, micro-patterned silicon cavities.
• To analyze the impact of chaotic boundaries and laser-machined hole patterns on wave behavior.
• To examine the persistence of time reversal and reciprocity symmetry in such complex systems.

Main Methods:

• Fabrication of thin silicon wafers with micro-patterned holes using laser machining.
• Experimental study of elastic wave propagation, inducing multiple scattering.
• Analysis of time reversal signal quality as a function of time interval and signal position.
• Investigation of time dilatation effects on re-emitted elastic waves.

Main Results:

• Chaotic behavior and multiple scattering were induced by irregular boundaries and hole patterns.
• Phononic band-like dispersion properties were observed with regular hole patterns.
• Time reversal and reciprocity symmetry were found to be robust, persisting despite mode mixing, anisotropy, and dissipation.
• Systematic data on time-reversal signal quality and time dilatation effects were presented.

Conclusions:

• Micro-patterned silicon wafers serve as effective systems for studying complex elastic wave phenomena.
• The inherent symmetries of elastic waves are remarkably resilient in strongly scattering and anisotropic solid-state cavities.
• This research provides insights into the fundamental physics of wave propagation in disordered media.