A journey through bound states in the continuum in periodic optical structures

Bound states in the continuum(BIC)were first identified by von Neumann and Wigner[1]almost a century ago.At that time,they pointed out an intriguing phenomenon:a state could be bound by a special oscillating potential distribution,even when the state’s energy is higher than the maximum of the potential.According to the principles taught in elementary quantum mechanics,the energy of such a state should lie within the continuum spectrum.