Let's imagine a hypothetical scenario where two individuals are gripping a rope, each holding one end. Person A proceeds to shake the rope in an up-and-down motion, thus generating a propagating wave that travels towards person B. Now, if person C, positioned between person A and B, engages in a comparable frequency of waving motion as that of the rope's wave, could the wave be redirected back to person A rather than reaching person B? Initially, this situation appears implausible, as person C does not physically interact with the rope held by person A and B, seemingly defying the possibility of achieving a 100% wave reflection similar to that observed in a perfect mirror. Nonetheless, this phenomenon finds explanation within the domain of physics and is known as the "bound state in the continuum (BIC)."
The study of BIC has encompassed diverse disciplines including quantum mechanics, optics, semi-conductors, and nano-optics. Utilizing this phenomenon facilitates the confinement of light particles, or photons, preventing their forward propagation. Moreover, BIC holds promise for the development of highly sensitive sensors. Previous research into BIC has predominantly focused on microscale and nanoscale contexts while investigations using visible structures to explain this phenomenon have been absent.
Recently, a research team led by Professor Junsuk Rho from the Department of Mechanical Engineering and the Department of Chemical Engineering and PhD candidates Dongwoo Lee, Jeonghoon Park, and Seokwoo Kim from the Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH) successfully demonstrated bound states in the continuum through the utilization of an acoustoelastic coupling structure for the first time. The research findings have been published in Extreme Mechanics Letters, one of the world's most influential journals in the field of mechanics.
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