Enhancing Antireflection Based on a Symmetry-Dependent Kerker Effect.

The significance of antireflection has persisted over time due to its numerous optical applications. To achieve broadband antireflection, multiple element-based designs using graded-index films or multiresonant nanostructures have been conventionally employed. In this work, we propose an additional degree of freedom in developing antireflection by manipulating the orientation angles of nanostructures to achieve the symmetry-dependent Kerker condition. Under the excitation of multipoles in higher-order resonances, which typically complicates the interference condition, the perfect Kerker condition is demonstrated without backward leakage of power at a wavelength significantly shorter than the excitation bandwidth of electric and magnetic dipoles. Such a condition can be directly linked to the symmetry of resonators and maximized by suppressing the near-field coupling and optimizing polarization-related spatial parities. We experimentally demonstrate the symmetry-dependent Kerker condition and polarization-independent antireflection at the midwave infrared range, which has attracted increasing attention in emerging imaging and sensing fields.