单晶金片上表面等离极化激元的定量近场表征
Quantitative near-field characterization of surface plasmon polaritons on monocrystalline gold platelets
AI总结：
本文利用近场显微镜研究单晶金片上的表面等离极化激元，发现掠入射角能最佳分离探针激发的SPPs振幅与相位信号，并提出模型提取波长和传播长度，为可见光下极化激元的定量分析提供了新方法。
摘要：
表面等离极化激元（SPPs）的亚波长限制特性使其在传感、光产生和太阳能转换等各种应用中极具吸引力。与干涉检测相结合的近场显微镜能够可视化SPPs的振幅和相位。然而，由于多个激发通道之间干涉产生的复杂波模式，在反射配置下对它们进行完整的定量表征具有挑战性。在此，我们展示了在可见光谱范围内，大型单晶金片上SPPs的近场测量结果。我们系统地研究了激发光的入射角对由原子力显微镜探针激发的SPPs的影响。我们发现，相对于金片边缘的掠入射角，这些SPPs的振幅和相位信号能最好地与其他信号分离。此外，我们引入了一个简单模型来解释在SPP振幅和相位分布之间观察到的相移。利用该模型，通过在远离金片边缘处分离并拟合信号，提取了探针激发等离激元的波长和传播长度。我们的实验结果与使用金折射率值的理论模型高度一致。所提出的完整表征SPP复波矢的方法，有望实现对可见光波长下不同材料中出现的极化激元的定量分析。
英文摘要：
The subwavelength confinement of surface plasmon polaritons (SPPs) makes them attractive for various applications such as sensing, light generation and solar energy conversion. Near-field microscopy associated with interferometric detection allows to visualize both the amplitude and phase of SPPs. However, their full quantitative characterization in a reflection configuration is challenging due to complex wave patterns arising from the interference between several excitation channels. Here, we present near-field measurements of SPPs on large monocrystalline gold platelets in the visible spectral range. We study systematically the influence of the incident angle of the exciting light on the SPPs launched by an atomic force microscope tip. We find that the amplitude and phase signals of these SPPs are best disentangled from other signals at grazing incident angle relative to the edge of the gold platelet. Furthermore, we introduce a simple model to explain the phase shift observed between the SPP amplitude and phase profiles. Using this model, the wavelength and propagation length of the tip-launched plasmons are retrieved by isolating and fitting their signals far from the platelets edges. Our experimental results are in excellent agreement with theoretical models using gold refractive index values. The presented method to fully characterize the SPP complex wavevector could enable the quantitative analysis of polaritons occurring in different materials at visible wavelengths.
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