Křápek V, Koh A L, Břínek L, Hrtoň M, Tomanec O, Kalousek R, Maier S A, Šikola T
Opt Express. 2015 May 4;23(9):11855-67. doi: 10.1364/OE.23.011855.
We present a study of the optical properties of gold crescent-shaped antennas by means of electron energy loss spectroscopy. These structures exhibit particularly large field enhancement near their sharp features, support two non-degenerate dipolar (i.e., optically active) localised surface plasmon resonances, and are widely tunable by a choice of their shape and dimensions. Depending on the volume and shape, we resolved up to four plasmon resonances in metallic structures under study in the energy range of 0.8 - 2.4 eV: two dipolar and quadrupolar mode and a multimodal assembly. The boundary-element-method calculations reproduced the observed spectra and helped to identify the character of the resonances. The two lowest modes are of particular importance owing to their dipolar nature. Remarkably, they are both concentrated near the tips of the crescent, spectrally well resolved and their energies can be tuned between 0.8 - 1.5 eV and 1.2 - 2.0 eV, respectively. As the lower spectral range covers the telecommunication wavelengths 1.30 and 1.55 μm, we envisage the possible use of such nanostructures in infrared communication technology.
我们通过电子能量损失谱对金新月形天线的光学特性进行了研究。这些结构在其尖锐特征附近表现出特别大的场增强，支持两种非简并偶极（即光学活性）局域表面等离子体共振，并且通过选择其形状和尺寸可实现广泛的调谐。根据体积和形状，我们在0.8 - 2.4 eV能量范围内解析出了所研究金属结构中多达四种等离子体共振：两种偶极模式和四极模式以及一种多模式组合。边界元法计算重现了观察到的光谱，并有助于确定共振的特性。由于其偶极性质，两个最低模式尤为重要。值得注意的是，它们都集中在新月形的尖端附近，光谱分辨率良好，其能量可分别在0.8 - 1.5 eV和1.2 - 2.0 eV之间调谐。由于较低的光谱范围覆盖了电信波长1.30和1.55μm，我们设想这种纳米结构在红外通信技术中的可能应用。
