This rule, which is related directly to the Huygens’ principle is one of the key tools for analyzing the properties of optical beams. The propagation of a beam of light can be determined completely by its phase and amplitude profiles at a given two-dimensional surface. We focus primarily on flat optical devices, holography, and beam-shaping applications as these are the key ingredients needed for the development of a new generation of optical devices which could find widespread applications in photonics.

In this article, we review the recent developments, potential, and opportunities of metasurfaces applications. Such components can be easily realized using a single lithographic step and is highly suited for patterning a variety of substrates, including nonplanar and soft surfaces. In contrast to conventional optical components which rely on thickness variation to induce a phase profile, metasurfaces facilitate the realization of arbitrary phase distributions using large arrays with sub-wavelength and ultrathin (tens of nanometers) features. Be it a simple lens or a sophisticated holographic element, the functionality of such components is dictated by their spatial phase response. The ability to engineer and shape the phase profile of optical beams is in the heart of any optical element.

Ghost Light by E.J. Stevens