Metallic nanostructures have offered not only the exciting opportunity to manipulate light waves in unconventional manners, but also the exciting potential to create customized nonlinear media with tailored high-order effects. Two particularly compelling directions of current interests are active plasmonics, where the optical properties can be purposely manipulated by external stimuli, and nonlinear plasmonics, which enable intensity-dependent frequency conversion of light. By exploring the interaction of these two directions, we leverage the electrical and optical functions simultaneously supported in nanostructured metals and demonstrate electrically-controlled nonlinear processes from plasmonic metamaterials. We show that a variety of nonlinear optical phenomena, including the wave mixing and the optical rectification, can be purposely modulated by applied voltage signals. In addition, electrically-induced and voltage-controlled nonlinear effects facilitate us to demonstrate the backward phase matching in a negative index material, a long standing prediction in nonlinear metamaterials. Other results to be covered in this talk include photon-drag effect in plasmonic metamaterials and ion-assisted nonlinear effects from plasmonic crystals in electrolytes. Our results reveal a grand opportunity to exploit plasmonic metamaterials as self-contained, dynamic electrooptic systems with intrinsically embedded electrical functions and optical nonlinearities for signal generation, information processing, and biochemical sensing.
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S. Lan, L. Kang, D. T. Schoen, S. P. Rodrigues, Y. Cui, M. L. Brongersma, and W. Cai, Nature Materials, 14, 807 (2015).
S. Lan, S. P. Rodrigues, Y. Cui, L. Kang, and W. Cai, Nano Letters, 16, 5074 (2016).