Mode-Interference-Induced Chiral Exceptional Points in Momentum Space

Non-Hermitian metasurfaces with chiral exceptional points (EPs) in their scattering matrices have garnered significant attention due to their potential for optical polarization manipulation and wavefront control. However, existing approaches predominantly operate under normal incidence conditions, limiting their application in the manipulation of chiral EPs in momentum space. Here, the wavelength-fixed manipulation of the chiral EPs across a wide-range momentum space using a polyatomic metasurface is realized, which is attributed to the effective modulation of the collective interference of guided-mode resonances excited by oblique transverse magnetic (TM) and transverse electric (TE) illuminations. Further, both theoretical and experimental analyses are conducted to explore the potential applications of the proposed design in the wavevector- and spin-selective manipulation of reflection intensity and optical encryption. This work provides a straightforward method to realize and manipulate chiral EPs in momentum space at a fixed operational wavelength, paving the way for designing polarization-selective and wavevector-selective devices. Manipulation of chiral EPs in momentum space is realized based on a polyatomic metasurface by strategically modulating the collective interference of guided-mode resonances excited by oblique TM and TE illuminations. Its potential applications in the wavevector- and spin-selective manipulation of reflection intensity and optical encryption are experimentally demonstrated. image