From Event: SPIE Nanoscience + Engineering, 2018
Second harmonic generation is one of the fundamental nonlinear optical processes that is at the heart of communication and sensing applications. Due to the underlying crystal symmetry, second harmonic generation in noble metal-nanostructures is dominated by metal/dielectric interfaces with only weak (magneto-dipole and quadrupolar) contributions coming from the bulk of the metal inclusions. Here we demonstrate that, in metamaterials, nonlinear contributions from individual plasmonic inclusions can add up together, resulting in the bulk nonlinear polarization. The resulting nonlinear response can be described in terms of volumetric second harmonic polarizability that relates unit-cell averaged nonlinear polarization to a product of unit-cell averaged fundamental fields. The amplitude of this effective nonlinear polarizability is comparable to that of common nonlinear crystals.
In order to analyze nonlinear response of the plasmonic nanowire arrays we compare experimental results to numerical solutions of Maxwell equations where second harmonic response is calculated using nonlinear hydrodynamic model. Numerical solutions of Maxwell equations are also used to analyze the spatial and spectral distributions of fundamental and nonlinear fields across the composites and, in the end, to guide and validate the development of analytical description of effective second harmonic polarizability. The developed analytical description of the second harmonic generation in plasmonic composites opens new avenues for engineering of nonlinear response.
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Viktor A. Podolskiy, Brian Wells, Anton Yu Bykov, Giuseppe Marino, Mazhar Nasir, and Anatoly Zayats, "Structural second order nonlinearity in metamaterials (Conference Presentation)," Proc. SPIE 10719, Metamaterials, Metadevices, and Metasystems 2018, 107191O (Presented at SPIE Nanoscience + Engineering: August 22, 2018; Published: 17 September 2018); https://doi.org/10.1117/12.2319665.5836031875001.