Arbitrary Wavefront Manipulation in Real Space and Momentum Space Based on Elliptical Structures

ABSTRACT

Leveraging elliptical structures with strong spatial continuity and anisotropy—while preserving real space arbitrary wavefront manipulation via the Pancharatnam–Berry (PB) phase—we generalize the manipulation to momentum space by exploiting the localized dipole momentum embedded in bound states in the continuum (BIC), thereby enhancing the flexibility of information transmission across the dual spaces for micro–nano devices and boosting information capacity. The proposed scheme utilizes the rotation characteristics of anisotropic elliptical structures to precisely modulate the polarization phase distribution in real space. In momentum space, defect perturbations are introduced to construct an independent geometric phase gradient, thereby flexibly tailoring the wavefront profiles of vertically emitting modes. Numerical results demonstrate that the designed unit cell exhibits excellent resonance stability and favorable linear phase modulation performance. The cross–polarization transmission efficiency in real space is approximately 25% at all orientation angles. The Q factor in momentum space can exceed 4000. Continuous phase modulation ranging from 0 to 2 can be realized in both spaces, with nearly zero crosstalk. Multifunctional integrated outputs such as beam deflection and focusing can be flexibly achieved in the near–infrared communication band.