Chen Jiawei, Wang Kai, Long Hua, Hu Hongbo, Han Xiaobo, Wang Bing, Lu Peixiang
Opt Express. 2017 Jan 23;25(2):1296-1307. doi: 10.1364/OE.25.001296.
We systematically study the contribution of local-field distribution to second-harmonic generation (SHG) in cross-shaped Ag nanohole arrays, which is usually covered by resonance enhancement effect. By increasing one arm-length of the centrosymmetric cross-shaped Ag nanohole, the local-field distribution varies from centrosymmetric to non-centrosymmetric, while the localized surface plasmon resonance peak is red-shifted to the wavelength of the pumping laser accordingly. Both experimental and stimulated results indicate that the contribution of the asymmetric local-field distribution to SHG is quantitatively separated from a strong resonance enhancement effect. It shows that the pure effective second-order nonlinear susceptibility increases as the asymmetric degree of local-field distribution increases, and the largest effective second-order nonlinear susceptibility is ~2.5 times to that in a centrosymmetric local-field distribution. Our results provide evidence for optimizing the design of nonlinear plasmonic nanoantennas and metasurfaces.
我们系统地研究了局域场分布对十字形银纳米孔阵列中二次谐波产生（SHG）的贡献，该贡献通常被共振增强效应所掩盖。通过增加中心对称十字形银纳米孔的一个臂长，局域场分布从中心对称变为非中心对称，同时局域表面等离子体共振峰相应地红移到泵浦激光的波长。实验和模拟结果均表明，不对称局域场分布对SHG的贡献已从强烈的共振增强效应中定量分离出来。结果表明，纯有效二阶非线性极化率随局域场分布不对称程度的增加而增大，最大有效二阶非线性极化率约为中心对称局域场分布时的2.5倍。我们的结果为优化非线性等离子体纳米天线和超表面的设计提供了依据。
