Theoretical and Numerical Investigation of Material-Driven Polymer GRIN Lens Optimization Design

This paper presents a systematic investigation into the design and performance of layered polymer gradient refractive index (GRIN) lenses. A material-driven optimization algorithm is proposed, which uses physical volume fractions of the constituent polymers to parameterize the refractive index distribution. By integrating effective medium theory with Sellmeier-based dispersion data, the algorithm ensures that the gradients remain within physically realizable material limits while better aligning with actual refractive index profiles. First, refractive index distribution models for first-order radial GRIN lenses and linear spherical radial GRIN lenses were derived based on material properties, establishing manufacturable lens parameterization expressions. Subsequently, simulation software was employed to model and compare a first-order GRIN doublet, a cemented doublet, a linear spherical radial GRIN lens, and a first-order GRIN aspheric lens. Numerical results demonstrate that the proposed GRIN structures exhibit superior performance in both monochromatic aberration suppression and chromatic control, particularly under large aperture conditions. For a lens system with a 50 mm focal length and a 25 mm entrance pupil diameter, the spherically symmetric GRIN lens achieves diffraction-limited chromatic performance, with its secondary spectrum reduced by over 70% compared to conventional cemented doublets. Furthermore, the first-order GRIN doublet maintains the smallest RMS spot size across multiple fields of view and exhibits the most stable aberration growth rate as the aperture increases. These results validate the feasibility of the material-driven GRIN modeling approach and provide theoretical support for high-performance, short-focal-length optical systems.