Towards the performance limit of catenary meta-optics via field-driven optimization

Catenary optics enables metasurfaces with higher efficiency and wider bandwidth, and is highly anticipated in the imaging system, super-resolution lithography, and broadband absorbers. However, the periodic boundary approximation without considering aperiodic electromagnetic crosstalk poses challenges for catenary optical devices to reach their performance limits. Here, perfect control of both local geometric and propagation phases is realized through field-driven optimization, in which the field distribution is calculated under real boundary conditions. Different from other optimization methods requiring a mass of iterations, the proposed design method requires less than ten iterations to get the efficiency close to the optimal value. Based on the library of shape-optimized catenary structures, centimeter-scale devices can be designed in ten seconds, with the performance improved by ~15%. Furthermore, this method has the ability to extend catenary-like continuous structures to arbitrary polarization, including both linear and elliptical polarizations, which is difficult to achieve with traditional design methods. It provides a way for the development of catenary optics and serves as a potent tool for constructing high-performance optical devices.