Embedded trapped modes in water waves and acoustics

Observation of trapped light within the radiation continuum

“…4b). These evidences quantitatively verify that we have observed the predicted bound state of light.We have observed an optical state that remains perfectly confined even though there exist symmetry-compatible radiation modes in its close vicinity; this realizes the long sought-after idea 7 of trapping waves within the radiation continuum, without symmetry incompatibility [5][6][7][8][10][11][12][13][14][15][16] . The state has a high quality factor (implying low loss and large field enhancement), large area, and strong confinement near the surface, making it potentially useful for chemical/biological sensing, organic light emitting devices, and large-area laser applications.…”

“…Such a bound 1 state can exist stably in a general class of geometries where all of its radiation amplitudes vanish simultaneously due to destructive interference. This method to trap electromagnetic waves is also applicable to electronic 12 and mechanical waves 14,15 .The propagation of waves can be easily understood from the wave equation, but the localization of waves (creation of bound states) is more complex. Typically, wave localization can only be achieved when suitable outgoing waves either do not exist or are forbidden due to symmetry incompatibility.…”

“…Here we predict and experimentally demonstrate that light can be perfectly confined in a patterned dielectric slab, even though outgoing waves are allowed in the surrounding medium. Technically, this is an observation of an "embedded eigenvalue" 9 -namely a bound state in a continuum of radiation modes-that is not due to symmetry incompatibility [5][6][7][8][10][11][12][13][14][15][16] . Such a bound 1 state can exist stably in a general class of geometries where all of its radiation amplitudes vanish simultaneously due to destructive interference.…”

“…Such a bound 1 state can exist stably in a general class of geometries where all of its radiation amplitudes vanish simultaneously due to destructive interference. This method to trap electromagnetic waves is also applicable to electronic 12 and mechanical waves 14,15 .…”

“…Furthermore, the trapping is destroyed by any generic perturbation to the potential. More recently, other counterexamples have been proposed theoretically in quantum systems [11][12][13] , photonics 5-8 , acoustic and water waves 14,15 , and mathematics 16 ; the proposed systems in refs. 6 and 14 are most closely related to what is demonstrated here.…”