Adjoint-based optimization of quadratic metalenses for wide field-of-view applications

Abstract

The design method of a metalens significantly impacts its actual performance. Conventional design approaches, such as the phase-matching approach, often fail to achieve the desired performance in metalenses with rapid phase changes due to mismatches between the actual and intended phase outputs of the meta-atoms. In this work, we employ an adjoint-based design method combined with level-set functions to partially address this issue. We present the design of a one-dimensional metalens with a quadratic-phase profile for wide-field-of-view applications. Our simulations show that the optimized design extends the FOV while maintaining focusing efficiency, compared to the conventional design with the same geometric numerical aperture of 0.9. This adjoint-based method provides an effective approach to improving the performance of wide-field-of-view metalenses and other metasurfaces with rapid phase changes, building upon the phase-matching framework.