Here we review our journey from metallic nanostructures to dielectric and semiconductor metasurfaces. We show how to employ metal non-linearity to stimulate a strongly anisotropic nonlinear response by symmetry breaking, despite their high Ohmic losses. Furthermore, we show how an ultra-thin surface of subwavelength dielectric nanostructures, e.g. silicon with negligible losses and multipolar characteristics, can enable enhanced light matter interaction for efficient third harmonic generation and ultra-fast light modulation. However, the centrosymmetric structure of silicon and the lack of quadratic nonlinearity, guided us towards exploiting semiconductor nanostructures, particularly III-V semiconductors. Subsequently, we demonstrate dielectric realization of AlGaAs nanoantennas for an efficient second harmonic generation, allowing the control of both directionality and polarization of nonlinear emission. This is enabled through the fabricated high-quality AlGaAs nanostructures embedded in an optically transparent low-index material. Our results open novel applications in ultra-thin light sources, light switches and modulators, ultra-fast displays, night-vision and other nonlinear optical metadevices based on resonant nanoparticles.
Lei Xu, Mohsen Rahmani, Dragomir N. Neshev, and Yuri S. Kivshar, "Optical frequency conversion at the nanoscale: metallic, dielectric, and semiconductor nanostructures (Conference Presentation)," Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 1054018 (Presented at SPIE OPTO: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2281498.5751515773001.
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