One-dimensional photonic bound states in the continuum

In 1985 Fridriech and Wintgen proposed a mechanism for bound states in the continuum based on full destructive interference of two resonances which can be easily applied to the two- and three-dimensional wave systems. Here we explicitly show that this mechanism can be realized in one-dimensional quantum potential well, owing to destructive interference of electron paths with different spin in tilted magnetic field. Due to one-by-one correspondence between the spin of the electron and the polarization state of light, we have found numerous bound states in the continuum in the one-dimensional photonic system and experimentally confirmed them. The experimental set-up consists of the one-dimensional photonic crystal conjugated with a liquid-crystalline anisotropic defect layer and covered by metal film. Bound states in the continuum have recently found application to sensing, lasing and optoelectronics, but have not been realised in 1D. Here, destructive interference of electron spin in a tilted magnetic field is shown to give rise to bound states in the continuum of a 1D layered photonic crystal.