Broadband Reflective Elastic Mode Conversion Enabled by a Single Row of Inclined Long-Slits

TL;DR

This paper demonstrates that a simple structure with inclined long-slits can achieve broadband conversion of elastic waves from longitudinal to transverse modes with high efficiency, leveraging intrinsic deformation modes.

Contribution

It introduces a minimal, robust design using a single row of inclined slits for broadband elastic wave mode conversion, a significant advance over complex existing methods.

Findings

Conversion rate exceeds 0.8 across 0.27 to 0.74 normalized frequency range

Achieves 93.1% relative bandwidth for mode conversion

Design is robust against geometric variations

Abstract

Broadband longitudinal-to-transverse mode conversion under normal incidence remains difficult to achieve, especially with structurally simple designs. Numerical simulations show that a single periodic row of inclined long-slits near a free surface enables high-efficiency broadband conversion, where the conversion rate exceeds 0.8 across a normalized-frequency range of 0.27 to 0.74, corresponding to a 93.1% relative bandwidth. The broadband response originates from two intrinsic deformation modes of the mass blocks between adjacent inclined slits: a rotational mode and a quadrupole mode. The spectral overlap of these two modes sustains a continuous high-efficiency band. The effect is robust against geometric variations, demonstrating that geometric asymmetry alone offers a minimal yet effective route to broadband elastic-wave mode conversion.