Gürdal Emre, Horneber Anke, Shaqqura Nadim, Meixner Alfred J, Kern Dieter P, Zhang Dai, Fleischer Monika
Institute for Applied Physics and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
Institute of Physical and Theoretical Chemistry and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany.
J Chem Phys. 2020 Mar 14;152(10):104711. doi: 10.1063/1.5139893.
In second harmonic generation (SHG), the energy of two incoming photons, e.g., from a femtosecond laser, can be combined in one outgoing photon of twice the energy, e.g., by means of a nonlinear crystal. The SHG efficiency, however, is limited. In this work, the harvested signal is maximized by composing a hybrid system consisting of a nonlinear crystal with a dense coverage of plasmonic nanostructures separated by narrow gaps. The method of self-assembled diblock-copolymer-based micellar lithography with subsequent electroless deposition is employed to cover the whole surface of a lithium niobate (LiNbO) crystal. The interaction of plasmonic nanostructures with light leads to a strong electric near-field in the adjacent crystal. This near-field is harnessed to enhance the near-surface SHG signal from the nonlinear crystal. At the plasmon resonance of the gold nanoparticles, a pronounced enhancement of about 60-fold SHG is observed compared to the bare crystal within the confocal volume of a laser spot.
在二次谐波产生（SHG）中，例如来自飞秒激光器的两个入射光子的能量可以通过非线性晶体等方式组合成一个能量翻倍的出射光子。然而，SHG效率是有限的。在这项工作中，通过构建一个由具有密集覆盖的等离激元纳米结构且被窄间隙隔开的非线性晶体组成的混合系统，使采集到的信号最大化。采用基于自组装双嵌段共聚物的胶束光刻法并随后进行化学镀来覆盖铌酸锂（LiNbO）晶体的整个表面。等离激元纳米结构与光的相互作用会在相邻晶体中产生强烈的近场电场。利用这个近场来增强非线性晶体的近表面SHG信号。在金纳米粒子的等离激元共振处，与激光光斑共焦体积内的裸晶体相比，观察到SHG有明显约60倍的增强。
