Elastic bound state in the continuum with perfect mode conversion

The partial or complete confinement of waves in an open system is omnipresent nature and wave-based materials technology. Here, we theoretically analyze experimentally observe the formation a trapped mode with perfect conversion (TMPC) between flexural longitudinal waves, by achieving quasi-bound state continuum (BIC) elastic wave system. latter allows quasi-BIC semi-infinite background plate when Fano resonance hybridizes balances their radiative decay rates. We demonstrate that Fabry-P\'erot realized simultaneously, TMPC formed BIC approaches infinite quality factor. Furthermore, show can be tuned continuously to through critical frequency conversion, which offers possibility arbitrarily high Our reported concept physical mechanism new routes achieve tunable factor systems.