Frequency-selective omni-directional scattering of light by weakly disordered periodic planar arrays of dielectric particles.

We show that disorder-induced interaction between guided modes and a flat band of low-Q radiating modes in planar arrays of dielectric particles can lead to frequency-selective omni-directional scattering of light. This phenomenon is numerically observed in planar arrays consisting of periodically arranged dielectric particles with small randomness in particle sizes. The flat band of low-Q radiating modes originates from coupling of Mie resonances of individual particles. The small structural randomness enables coupling between the guided modes and the radiating modes with overlapping spectral ranges. Through interaction with the flat band of low-Q radiating modes, the guided modes can be effectively excited by far-field sources from any direction, and make key contribution to the frequency-selective omni-directional scattering. The frequency-selective omni-directional scattering has many potential applications such as display and sensing.