Kataja Mikko, Pourjamal Sara, van Dijken Sebastiaan
Opt Express. 2016 Feb 22;24(4):3562-71. doi: 10.1364/OE.24.003562.
Subwavelength metallic particles support plasmon resonances that allow extreme confinement of light down to the nanoscale. Irradiation with left- and right hand circularly polarized light results in the excitation of circular plasmon modes with opposite helicity. The Lorenz force lifts the degeneracy of the two modes in magnetic nanoparticles. Consequently, the confinement and frequency of localized surface plasmon resonances can be tuned by an external magnetic field. In this paper, we experimentally demonstrate this effect for nickel nanoparticles using magnetic circular dichroism (MCD). Besides, we show that non-local surface lattice resonances in periodic arrays of the same nanoparticles significantly enhance the MCD signal. A numerical model based on the modified long wavelength approximation is used to reproduce the main features in the experimental spectra and provide design rules for large MCD effects in sensing applications.
亚波长金属颗粒支持等离子体共振，这种共振能将光极度限制到纳米尺度。用左旋和右旋圆偏振光照射会激发具有相反螺旋度的圆等离子体模式。洛伦兹力消除了磁性纳米颗粒中这两种模式的简并性。因此，局部表面等离子体共振的限制和频率可以通过外部磁场进行调节。在本文中，我们使用磁圆二色性（MCD）实验证明了镍纳米颗粒的这种效应。此外，我们表明相同纳米颗粒的周期性阵列中的非局部表面晶格共振会显著增强MCD信号。基于修正长波长近似的数值模型用于重现实验光谱中的主要特征，并为传感应用中的大MCD效应提供设计规则。
