Broadband evolution of phononic-crystal-waveguide eigenstates in real- and k-spaces

Area of Science:

• Acoustics
• Condensed Matter Physics
• Materials Science

Background:

• Phononic band-gap structures offer advanced control and guiding of sound waves.
• Phononic crystals with defect rows effectively guide acoustic waves, primarily studied in the frequency domain.
• Frequency-domain analysis omits crucial information about acoustic field phase and eigenstate coupling.

Purpose of the Study:

• To investigate wave field evolution in phononic crystal waveguides beyond the limitations of frequency-domain analysis.
• To reveal the dynamics of eigenstate-energy redistribution and coupling in acoustic waveguides.
• To introduce and demonstrate the utility of k-t space analysis in phononics.

Main Methods:

• Implementation of an ultrafast technique to probe wave field dynamics.
• Analysis of acoustic wave propagation in straight and L-shaped phononic crystal surface-phonon waveguides.
• Utilizing both real-space and k-space (wavevector-time space) in two spatial dimensions.

Main Results:

• Direct observation of wave field evolution in phononic crystal waveguides.
• Detailed revelation of eigenstate-energy redistribution processes.
• Demonstration of coupling between different frequency-degenerate eigenstates.

Conclusions:

• The k-t space approach provides a comprehensive understanding of acoustic wave behavior in phononic waveguides, complementing traditional frequency-domain methods.
• This technique unveils previously hidden dynamics of energy transfer and state coupling.
• The methodology holds potential for characterizing acoustic metamaterials and other advanced acoustic systems.