Wunderlich Sarina, Peschel Ulf
Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg, Germany.
Opt Express. 2013 Aug 12;21(16):18611-23. doi: 10.1364/OE.21.018611.
Second Harmonic Generation (SHG) is a widely used tool to study surfaces. Here we investigate SHG from spherical nanoparticles consisting of a dielectric core (radius 100 nm) and a metallic shell of variable thickness. Plasmonic resonances occur that depend on the thickness of the nanoshells and boost the intensity of the Second Harmonic (SH) signal. The origin of the resonances is studied for the fundamental harmonic and the second harmonic frequencies. Mie resonances at the fundamental harmonic frequency dominate resonant effects of the SH-signal at low shell thickness. Resonances excited by a dipole emitting at SH frequency close to the surface explain the enhancement of the SHG-process at a larger shell thickness. All resonances are caused by surface plasmon polaritons, which run on the surface of the spherical particle and are in resonance with the circumference of the sphere. Because their wavelength critically depends on the properties of the metallic layer SHG resonances of core-shell nanoparticles can be easily tuned by varying the thickness of the shell.
二次谐波产生（SHG）是一种广泛用于研究表面的工具。在此，我们研究了由介电核心（半径100纳米）和可变厚度金属壳组成的球形纳米颗粒的SHG。发生了等离子体共振，其取决于纳米壳的厚度并增强了二次谐波（SH）信号的强度。研究了基波和谐波频率下共振的起源。在低壳厚度下，基波频率处的米氏共振主导了SH信号的共振效应。在靠近表面的SH频率处由偶极子发射激发的共振解释了在较大壳厚度下SHG过程的增强。所有共振都是由表面等离子体激元引起的，它们在球形颗粒表面传播并与球的周长共振。由于它们的波长严格取决于金属层的性质，核壳纳米颗粒的SHG共振可以通过改变壳的厚度轻松调节。
