We demonstrate bound states in the first TE and TM diffraction continua (BSC) in a linear periodic array of dielectric spheres in air above the light cone. We classify the BSCs according to the symmetry specified by the azimuthal number $m$, the Bloch wave vector $\beta$ directed along the array, and polarization. The most simple symmetry-protected TE and TM polarized BSCs have $m=0$ and $\beta =0$ and occur in a wide range of the radii of the spheres and dielectric constants. More complicated BSCs with $m\ne 0$ and $\beta =0$ exist only for a selected radius of the spheres at a fixed dielectric constant. We also find robust Bloch BSCs with $\beta \ne 0$ and $m=0$. We present also the BSCs embedded into two and three diffraction continua. We show that the BSCs can be easily detected by the collapse of the Fano resonance for scattering of electromagnetic plane waves by the array.

• Received 19 June 2015

DOI:https://doi.org/10.1103/PhysRevA.92.023816