Nanostructured materials offer many advantages over bulk materials in nonlinear optical phenomena. For example, the subwavelength scale allows the neglect of phase-matching issues. The ability to control tight confinement and large resonant enhancement of electromagnetic fields also results in higher nonlinear frequency conversion efficiencies than bulk materials. Compared with plasmonic nanostructures, high-index dielectric nanostructures render larger mode volumes and show great promise for enhanced nonlinear optical processes. In this work, we present resonantly enhanced second-harmonic generation from L-shaped AlGaAs nanoantennas. By tuning the nanostructure thickness, arm length, and width, the overlap of resonances at fundamental and second-harmonic wavelengths can be achieved using any pump wavelength in a broad near-infrared spectral region. We predict SHG efficiency exceeding ${4} \times {{10}^{ - 3}}$ with a pump intensity of ${1}\;{{\rm GW/cm}^2}$ at two representative pump wavelengths of 1675 and 1800 nm. Our findings are valuable for applications involving all-dielectric nanoantennas, such as efficient sensing and single biomolecule tracking microscopy.

中文翻译：

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L形AlGaAs纳米天线增强了二次谐波的产生

纳米结构材料在非线性光学现象方面比块状材料具有许多优势。例如，亚波长范围允许忽略相位匹配问题。控制严格限制和大幅度增强电磁场的能力也导致了比块状材料更高的非线性频率转换效率。与等离激元纳米结构相比，高折射率介电纳米结构呈现更大的模式体积，并显示出增强非线性光学过程的巨大希望。在这项工作中，我们介绍了从L形AlGaAs纳米天线共振增强的二次谐波产生。通过调整纳米结构的厚度，臂长和宽度，使用宽泛的近红外光谱区域中的任何泵浦波长，都可以实现基波和二次谐波波长的谐振重叠。我们预计SHG效率将超过$ {4} \倍{{10} ^ {-3}} $，泵浦强度为$ {1} \; {{\ rm GW / cm} ^ 2} $，在两个代表泵浦波长1675和1800 nm 。我们的发现对于涉及全介电纳米天线的应用是有价值的，例如高效感测和单个生物分子跟踪显微镜。