Fourier-component engineering to control light diffraction beyond subwavelength limit

Abstract Resonant physical phenomena in planar photonic lattices, such as bound states the continuum (BICs) and Fano resonances with 100% diffraction efficiency, have garnered significant scientific interest recent years owing to their great ability manipulate electromagnetic waves. In conventional theory, a subwavelength period is considered prerequisite achieving highly efficient resonant phenomena. Indeed, most of previous studies, that treat anomalous resonance effects, utilize quasiguided Bloch modes at second stop bands open region. Higher (beyond second) beyond limit attracted little attention thus far. principle, are governed by superposition scattering processes, higher Fourier harmonic components periodic modulations lattice parameters. But only some dominant band edges Bragg conditions. Here, we present new principles light diffraction, enable identification causing multiple orders stopbands, show unwanted can be suppressed engineering components. Based on principles, novel Fourier-component-engineered (FCE) metasurfaces introduced analyzed. It demonstrated these FCE appropriately engineered spatial dielectric functions exhibit BICs even limit.