Structuring visible light with dielectric metasurfaces

In less than ten years, the research field of metasurfaces has exploded, with over a thousand papers every year. There are a number of factors contributing to such global success. One important aspect is that nano-fabrication technologies are evolving fast with, for example, materials depositions and lithography resolutions not available just a few years ago. Furthermore, even if most of the metasurface design and fabrication processes may be far from being scalable to large areas typical of consumer products, there is a major interest from large industrial players looking for small-footprint metasurfaces to be integrated in lightweight and wearable optical devices, e.g. for augmented and virtual reality. From this point of view, the possibility of integrating the optical components production in standard electronics manufacturing is also a crucial aspect. All of this progress and interest have also triggered the development of easy-to-use simulation software with built-in routines specific for metasurface design, further contributing to the metasurface success. Among all the possible factors though, the possibility of implementing unprecedented optical functions by means of metasurfaces is still the main motivation. This Topical Review does not discuss technical aspects of metasurfaces fabrication. It is instead devoted to highlight what has been realized in particular with dielectric metasurfaces for visible light, with special emphasis on the fewer situations where the metasurface approach may be the only solution to the problem. With no doubt of missing important contributions among the enormous related literature, this Topical Review also tries to include direct comparison to other standard approaches in optics, to possibly capture the broader interest of researchers that are not directly involved in the metasurfaces research field.