Temporal Refraction in an Acoustic Phononic Lattice

Area of Science:

• Acoustics
• Condensed Matter Physics
• Materials Science

Background:

• Phononic lattices control acoustic wave propagation.
• Temporal boundaries introduce dynamic changes to material properties.
• Understanding wave behavior at dynamic interfaces is crucial for novel acoustic devices.

Purpose of the Study:

• To experimentally demonstrate temporal refraction of acoustic waves in a phononic lattice.
• To investigate frequency translation and wavelength preservation of acoustic signals at temporal boundaries.
• To establish phononic analogs of classical Snell and Fresnel relationships for temporal interfaces.

Main Methods:

• Utilizing a phononic lattice with a step change in grounding stiffness to create a temporal boundary.
• Inducing a discontinuous change in acoustic group velocity across the temporal boundary.
• Analyzing the frequency and wavelength of transmitted acoustic signals.

Main Results:

• First experimental evidence of temporal refraction for acoustic waves.
• Observed frequency translation of incident signals with constant wavelength.
• Established phononic analogs of Snell and Fresnel laws for temporal boundaries.

Conclusions:

• Temporal refraction of acoustic waves is experimentally achievable in phononic lattices.
• The demonstrated phenomenon allows for precise control over acoustic signal frequencies.
• This work paves the way for designing advanced acoustic metamaterials with tunable slow sound properties.