Introducing Metalenses Through Classical Optics and Huygens’ Principle

What is it about?

This paper offers a clear and accessible introduction to metalenses using the language of classical optics. Instead of starting from advanced nanophotonics or electromagnetic simulations, the study explains how metalenses work by connecting them to well-known concepts such as wavefronts, phase, and Huygens’ principle. A central result of the work is a new derivation of the generalized Snell’s law for metasurfaces. While this law had previously been obtained using Fermat’s principle of least time, this paper shows—step by step—how the same law can be derived directly from Huygens’ principle. This approach reveals the physical meaning of metasurfaces as engineered wavefront shapers, where abrupt phase changes at an interface control the direction of light propagation. By framing metalenses within classical optics, the article bridges traditional lens theory and modern flat optics, making the topic accessible to students, educators, and researchers entering the field.

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Photo by Nadine E on Unsplash

Photo by Nadine E on Unsplash

Why is it important?

Metalenses are often perceived as conceptually complex because they are introduced through advanced formalisms. This work lowers that barrier by showing that their fundamental behavior can be understood using classical wave optics. The derivation of Snell’s law for metasurfaces using Huygens’ principle is particularly important because it provides an intuitive and physically transparent explanation of how phase discontinuities bend light. This perspective complements earlier landmark results based on Fermat’s principle and strengthens the conceptual foundations of metasurface optics. The paper is especially valuable for education and interdisciplinary research, as it helps integrate metasurfaces into standard optics curricula and supports a deeper understanding of flat optical devices.

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