Resonant scattering of acoustic wave: multipole theory, acoustic radiation force and torque

   You are invited to attend a Seminar on Wednesday, October 22 2025, at 14:00

  Classroom Building, Room 011

Resonant scattering of acoustic wave: multipole theory, acoustic radiation force and torque

Prof. Mihail Petrov

Assoc. Prof., ITMO University

 Abstract

This seminar presents an overview of resonant scattering and manipulation of acoustic waves through the lens of optical physics and nanophotonics. Drawing direct analogies between sound and light, we begin with the fundamental equations of acoustic wave propagation, highlighting their correspondence to electromagnetic theory and the concepts of impedance, polarizability, and radiation pressure.

We then examine a range of acoustic resonators and meta-atoms—including Helmholtz cavities, coiled structures, and coupled non-Hermitian systems—showing how their symmetry and resonance properties parallel those of optical resonators and plasmonic nanostructures. Building on this foundation, the multipole theory of acoustic scattering is developed to describe the acoustic analogues of electric and magnetic dipoles, higher-order multipoles, and Willis coupling, providing insight into tailored scattering and high-Q resonant effects.

Finally, we explore acoustic radiation forces and torques from an optical-force perspective, illustrating how concepts from optical tweezers and light–matter interaction translate to structured acoustic fields. Throughout the seminar, emphasis is placed on the shared physical principles that bridge acoustics and photonics, offering a unified view of wave–matter interactions and guiding the design of next-generation acoustic metamaterials.

Contents:

• Intro: basic theory and the key equations
• Acoustic resonators: symmetry of resonators; Helmholtz resonators; coiled metaatoms; coupling of resonators and non-Hermitian effects; 
• Multipolar theory of scattering: acoustic polarizability, Willis coupling, high-Q effects
• Acoustic radiation force and torque from optical forces perspective