Nonlinear Plasmonic Metasurfaces

Abstract

The nonlinear optical response of materials allows optical functionality not seen in linear devices, such as switching, wavelength conversion, and adaptive optics. Unfortunately, the nonlinear optical response is weak in naturally occurring materials, making many ultrafast information processing applications impractical from an efficiency point of view. Nonlinear plasmonic metasurfaces, as a subset of metamaterials, aim to provide a more efficient and functional nonlinear optical response by tailoring the configuration of nanostructures. Metasurfaces are compact, cascadable, and easy to fabricate with established planar technologies, and therefore deserve particular attention. In this review, advances in nonlinear plasmonic metasurfaces are presented, including theoretical approaches, design methodologies, and key demonstrations of functionality. The theoretical approach first considers the linear response of the plasmonic metal and then uses this to calculate the nonlinear scattering. Design methodologies are considered including limits on gap size enhancements, tunneling and charging effects, and thermal management. Key demonstrations such as efficiency in wavelength conversion, functional wavelength conversion, and switching are also reviewed. Finally, an outlook on the future development in this field of research is offered, aiming at efficient and ultrafast optical information processing.

Nonlinear plasmonic metasurfaces

“…41 Consequently, considerable efforts have been taken to demonstrate the usefulness of nonlinear metasurfaces. 12,41,43,56,74 Despite impressive amount of progress, nonlinear metasurfaces have not yet truly rivalled conventional materials. This is because several challenges still exist, such as relatively low material damage threshold levels, difficulties in fabricating 3D metamaterials and naturally the intrinsic losses of metals.…”

“…Before proceeding, we note that a recent review focusing on the design considerations of metasurfaces exists. 74 In general, two different approaches to understand nonlinear metasurfaces can be taken. First, most of the numerical approaches mentioned above can be extended to periodic structures by using the Floquet-Bloch theory, periodic Green's functions and/or appropriate boundary conditions.…”

“…Consequently, numerous investigations have been carried out during the past decade in order to understand and utilize nonlinear responses of plasmonic nanoparticles. 12,54,56,74 Despite steady progress, many challenges still remain raising a question of whether nonlinear plasmonic metamaterials could ever rival traditional nonlinear materials.…”

“…In addition, several reviews exist already on this topic with their emphasis on material aspects, fabrication, quantum effects and exotic nonlinear phenomena. 12,42,49,54,56,71,74 Therefore, here we exclude those considerations and instead focus on discussing principles of nonlinear optics, modelling aspects and SHG-emitting metasurfaces. We highlight problems associated with previous approaches and discuss how those could be alleviated by utilizing lattice and inter-particle effects, such as surface lattice resonances (SLRs).…”

Recent Progress in Active Optical Metasurfaces

“…A number of studies have been performed to explore a variety of fundamental phenomena of nonlinear metasurfaces, such as nonlinear generation selectivity, nonlinear phase and wavefront modulation, ultrafast response, etc. Given the importance and rapid development of nonlinear metasurfaces, a few review papers that are dedicated to different aspects of nonlinearity in metasurfaces have recently been published …”