Canfield Brian K, Husu Hannu, Laukkanen Janne, Bai Benfeng, Kuittinen Markku, Turunen Jari, Kauranen Martti
Institute of Physics, Optics Laboratory, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland.
Nano Lett. 2007 May;7(5):1251-5. doi: 10.1021/nl0701253. Epub 2007 Mar 31.
We demonstrate that second-harmonic generation (SHG) from arrays of non-centrosymmetric T-shaped gold nanodimers with a nanogap arises from asymmetry in the local fundamental field distribution and is not related strictly to nanogap size. Calculations show that the local field contains orthogonal polarization components not present in the exciting field, which yield the dominant SHG response. The strongest SHG responses occur through the local surface susceptibility of the particles for a fundamental field distributed asymmetrically at the particle perimeters. Weak responses result from more symmetric distributions despite high field enhancement in the nanogap. Nearly constant field enhancement persists for relatively large nanogap sizes.
我们证明，具有纳米间隙的非中心对称T形金纳米二聚体阵列产生的二次谐波产生（SHG）源于局部基波场分布的不对称性，并不严格取决于纳米间隙的大小。计算表明，局部场包含激发场中不存在的正交偏振分量，这些分量产生了主要的SHG响应。对于在颗粒周边不对称分布的基波场，最强的SHG响应是通过颗粒的局部表面极化率产生的。尽管纳米间隙中场增强很高，但由于分布更对称，响应较弱。对于相对较大的纳米间隙尺寸，场增强几乎保持恒定。
