Background: Metamaterials (MMs) are smartly engineered structures with rationally designed, nanostructured building blocks that allow us to build devices with distinct responses to light, acoustic waves, and heat flows that are not attainable with naturally available materials. Advances: The latest developments have shown that optical metasurfaces comprising a class of optical MMs with a reduced dimensionality can exhibit exceptional abilities for controlling the flow of light; achieve the anomalously large photonic density of states; and, similar to their bulk analog, provide superresolution imaging. Such a planar photonics technology is expected to facilitate new physics and enhanced functionality for devices that are distinctly different from those observed in their three-dimensional MM counterparts. As a result, this technology will enable new applications in imaging, sensing, data storage, quantum information processing, and light harvesting. Outlook: The recent progress in optical metasurfaces can address the major issues hampering the full-scale development of MM technology, such as high loss, cost-ineffective fabrication, and challenging integration. The studies of new, low-loss, tunable plasmonic materials—such as transparent conducting oxides and intermetallics—that can be used as building blocks for metasurfaces will complement the exploration of smart designs and advanced switching capabilities. This progress in metasurface design and realization will lead to novel functionalities and improved performance and may result in the development of new types of ultrathin metasurface designs with unparalleled properties, including increased operational bandwidths and reduced losses. These new designs would also be compatible with planar, low-cost manufacturing. In turn, these advances will lead to ultrathin devices with unprecedented functionalities, ranging from dynamic spatial light modulation to pulse shaping and from subwavelength imaging or sensing to novel quantum optics devices.

Plasmonics is a research area merging the fields of optics and nanoelectronics by confining light with relatively large free‐space wavelength to the nanometer scale ‐ thereby enabling a family of novel devices. Current plasmonic devices at telecommunication and optical frequencies face significant challenges due to losses encountered in the constituent plasmonic materials. These large losses seriously limit the practicality of these metals for many novel applications. This paper provides an overview of alternative plasmonic materials along with motivation for each material choice and important aspects of fabrication. A comparative study of various materials including metals, metal alloys and heavily doped semiconductors is presented. The performance of each material is evaluated based on quality factors defined for each class of plasmonic devices. Most importantly, this paper outlines an approach for realizing optimal plasmonic material properties for specific frequencies and applications, thereby providing a reference for those searching for better plasmonic materials.

A plasmonic antenna array is used to control the propagation of a light beam across an interface.

New materials are being developed that meet the requirements for nanoscale photonics.