Metasurfaces have attracted significant attention owing to their broad capability to achieve exotic electromagnetic responses, and their potential as optical devices for wavefront control. Wide ranging materials may be used to form metasurfaces including noble and non-noble metals, oxides, ceramics, phase change materials, and semiconductors, permitting versatile and reconfigurable properties ideal for applications. In particular, applications that affect the science and technology of light—i.e., photonics—are of interest and will continue to grow in importance as our society becomes more digitally connected, but yet environmentally conscious.
The fields of metasurfaces1,2 and gradient index metasurfaces3 have been explored for nearly 20 years and 15 years, respectively. In 2003, the properties of single layer metamaterials—originally termed metafilms—were theoretically explored, and the discrete assembly of scatterers was treated as a continuous distribution of electric and magnetic polarization densities.1 Single layer metamaterials were also experimentally explored, and in 2004 it was shown that an effective magnetic response could be obtained from split-ring resonators in the terahertz4 and infrared5 regimes. The concept of gradient index single layer metamaterials was experimentally demonstrated in 2006 at microwave frequencies, where a negative index focusing lens was shown.3 The term “metasurface” came to the fore in 2009, where researchers showed that a single functional layer of metamaterial could be used for novel waveguide structures.2 Indeed, the use of few-layer metasurfaces has demonstrated novel functionality including perfect absorption6 and linear polarization conversion and anomalous refraction.7
However, more recently there has been renewed interest in gradient index metasurface—particularly in the near infrared and optical wavelength regimes. Although structures, materials, and similar results were demonstrated in the late 1990s,8,9 there has none-the-less been some impressive results shown over the last decade.10–17 This special issue highlights the state-of-the-art in metasurface photonic devices including recent advances in theory, numerical simulation, fabrication methods, and spectroscopic characterization that are advancing the field. Original research articles are accompanied by invited tutorials and perspectives that offer deep physical insight and provide an exciting outlook on future research.
The “Metasurfaces for Photonic Devices” Special Topic in the Journal of Applied Physics offers an overview of the most active research areas currently under investigation in the broad field of metasurfaces while also highlighting their importance for photonic applications. In particular, featured topics show demonstration of photonic devices including absorbers, filters, holography, lenses, and achromatic lenses. These examples are carried out across a large portion of the electromagnetic spectrum ranging from microwave18,19 and terahertz20–24 frequencies to near infrared25,26 and optical27–30 wavelengths. Several works show a host of topics and exotic phenomena supported by metasurfaces including tailoring of dark modes through hybridization, generation of achromatic Airy beams, bound states in the continuum (BIC), tunable plasmonic response with liquid crystals, and parameter retrieval.
We are deeply indebted to the Journal of Applied Physics Lead Editors for the Special Topic, Professors Masayoshi Tonouchi and Jaime Gómez Rivas for their supportive and enthusiastic role. We also thank the wonderful staff of AIP Publishing for correspondence with invited authors, preparing the Call for Papers, and promoting the papers published in the collection.
