Nonlinear Metasurfaces for Optical Applications

Metasurfaces have seen dramatic progress in broad band and large area systems recently and advances toward real applications are accelerating. While linear properties of metasurfaces are increasingly entering the engineering space, applications of nonlinear metasurface properties are emerging. Detecting optical signals in the mid and long wave infrared, and the generation, detection and conversion of single photons for quantum information applications are significant to a range of Air Force technologies and drive the research to increase performance and functionality. We explore how nonlinear properties of metasurfaces can be engineered for quantum information applications. We show that nonlinear multipolar interference allows both a non-reciprocal and unidirectional nonlinear generation from nanoelements, with the direction of nonlinear generation preserved with respect to a fixed laboratory coordinate system when reversing the direction of the fundamental field. This arises due to the existence of common (electric or magnetic) pathways inducing the electric and magnetic Mie resonances via a nonlinear interaction, such that switching the phase of one (electric or magnetic) of the vectors of the fundamental field can change simultaneously the phase of all (electric and magnetic) nonlinearly generated multipoles. These effects arise due to the nonlinear response of the component materials and we are actively pursuing novel materials systems and growth procedures to produce structures with controlled response. In order to develop such systems, precise control of structural dimensions at nanometric length scales is needed as well as plasmonic materials which are more resilient to nonlinear excitation intensities. A focus of our work is to explore novel materials systems that combine the functionality needed for nonlinear plasmonic metasurfaces and dynamic optical systems. This system is a useful example of where the engineering of materials response through structure to achieve desired optical properties can enable new potential technologies.