Inverse design in flat optics

Due to the sub-wavelength resolution, compact size, and ease of integration, flat optics has emerged as a pivotal player for applications in diffractive metalens, structured-light generation, holograms, nonlocal metasurfaces, etc. In the design of flat optics devices, the traditional forward design method demonstrates insurmountable limitations while inverse design has developed into an indispensable approach to focus designers only on high-level optical functionalities while handing over the task of finding conforming structures to machines. Here, we outline a cross-section of main advances of inverse design in flat optics: moving from basic theories and algorithms to further developments and diversified applications.