Experimental Observation of Optical Bound States in the Continuum

Abstract

We present the experimental observation of bound states in the continuum. Our experiments are carried out in an optical waveguide array structure, where the bound state (guided mode) is decoupled from the continuum by virtue of symmetry only. We demonstrate that breaking the symmetry of the system couples this special bound state to continuum states, leading to radiative losses. These experiments demonstrate ideas initially proposed by von Neumann and Wigner in 1929 and offer new possibilities for integrated optical elements and analogous realizations with cold atoms and optical trapping of particles.

Bloch surface eigenstates within the radiation continuum

“…Thus, theoretical explorations to discover simpler, easily realizable, and more robust systems that can contain embedded eigenvalues are of great interest. Embedded eigenvalues have also been explored in Maxwell's equations [17][18][19][20][21][22][23][24][25][26][27][28][29] and in the acoustic and water wave equations. [30][31][32][33][34][35][36][37][38] One occasion is when the spectrum of the problem can be separated by space group symmetry and when an oddsymmetry bound state lies in the continuum spectrum of the even states.…”

“…[30][31][32][33][34][35][36][37][38] One occasion is when the spectrum of the problem can be separated by space group symmetry and when an oddsymmetry bound state lies in the continuum spectrum of the even states. [17][18][19][20][21][22][23][30][31][32][33][34] Embedded states that do not rely on symmetry separability have received much attention, [10][11][12][13][14][15][16][24][25][26][27][28][29][35][36][37][38] but have never been experimentally verified, primarily because they are fragile to perturbations. In this work, we identify theoretically a new realization of an embedded eigenvalue in a PhC system that does not rely on symmetry, yet should be easily realizable.…”

Tamm–Hubbard surface states in the continuum

“…Bound states in the continuum (BIC) have been generally regarded as fragile states occurring in a few special systems with tailored potential [15,16,17,18], generally decaying into resonance states by small perturbations [19] and thus of low physical relevance. In the simplest case, BIC can arise from destructive quantum interference of the decay channels to the continuum [20,21,22,23], for example by virtue of a simple symmetry constraint [24]. Surface BIC of this kind in a tight-binding lattice model have been suggested, for example, in Ref.…”

Trapping of light with angular orbital momentum above the light cone

“…Such localized solutions of the Maxwell equations are known as the bound states in the continuum (BSC) and were first reported by von Neumann and Wigner [24]. The BSCs are of immense interest in optics thanks to experimental opportunity to confine light despite that outgoing waves are allowed in the surrounding medium [22,25,26,27,28,29]. A periodic infinite array of dielectric spheres illuminated by a plane wave (blue arrow).…”