Hashimoto Mamoru, Ashida Koichiro, Yoshiki Keisuke, Araki Tsutomu
Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
Opt Lett. 2009 May 1;34(9):1423-5. doi: 10.1364/ol.34.001423.
We have studied the enhancement of second-harmonic generation (SHG) from self-assembled monolayers on Au surfaces excited by radially polarized beams. The electric field at the metal surface was enhanced by constructive interference between the incident and the reflected beams due to a longitudinal field, which is the field parallel to the optical axis, generated around the focus by the radially polarized beam. Since even-order nonlinear phenomena are surface sensitive, the combination of SHG and a radially polarized beam has the potential to be a powerful new imaging tool for characterization of metal surfaces. The SHG signal excited by the radially polarized beam was about 3 times higher than that excited by a linearly polarized beam; in addition, the SHG from a 7-(dimethylamino)-4-methylcoumarin-3-isothiocyanate monolayer was about 1.3 times higher than that from a bare Au substrate.
我们研究了径向偏振光束激发金表面自组装单分子层产生的二次谐波（SHG）增强情况。由于径向偏振光束在焦点周围产生的纵向场（即平行于光轴的场），入射光束与反射光束之间的相长干涉增强了金属表面的电场。由于偶数阶非线性现象对表面敏感，SHG与径向偏振光束的结合有可能成为一种强大的新型成像工具，用于表征金属表面。径向偏振光束激发的SHG信号比线性偏振光束激发的信号高约3倍；此外，7-（二甲基氨基）-4-甲基香豆素-3-异硫氰酸酯单分子层产生的SHG比裸金基底产生的SHG高约1.3倍。
