Achromatic multi-level diffractive lenses and related applications

Achromatic multilevel diffractive lenses (AMDLs) represent a breakthrough in flat optics by overcoming chromatic aberration with practical manufacturability. This review examines their evolution from concepts to state-of-the-art devices (2016–2025), analyzing design methods, fabrication, limitations, and applications. We trace the development from zone plates to free-form AMDLs, highlighting the shift from analytical to computational design. The review explores inverse optimization algorithms like direct binary search and global optimization for achieving broadband achromatic performance. Manufacturing advances are categorized, from lithography for centimeter-scale devices to emerging techniques such as 3D printing and laser direct writing. Theoretical analysis establishes fundamental trade-offs between lens diameter, numerical aperture, bandwidth, and efficiency. We compare AMDLs with achromatic metalenses to outline the advantages and trade-offs of each paradigm. Furthermore, we examine the integration of artificial intelligence in AMDL design, from correction algorithms to end-to-end optimization. This synergy of computational optics, advanced manufacturing, and machine learning enables compact, high-performance optical systems for consumer electronics, scientific instrumentation, and photonic technologies, providing engineers with key insights and future research directions.