Esteban R, Vogelgesang R, Kern K
Max Planck Institute für Festkörperforschung, 70569 Stuttgart, Germany.
Opt Express. 2009 Feb 16;17(4):2518-29. doi: 10.1364/oe.17.002518.
We simulate apertureless near-field optical imaging and obtain phase and amplitude scans of structured substrates for elastic scattering. The solution of the three-dimensional Maxwell equations does not involve approximations and we include large tips and substrates, strong interaction, interferometric detection and demodulation at higher harmonics. Such modeling represents a significant step towards quantitative simulations and offers the attractive possibility to study the individual influence of each relevant experimental parameter. We typically obtain highly localized signatures of the interaction of the tip with gold inclusions, superposed on a slowly varying background signal. The relative importance of both contributions and the achievable lateral resolution are strongly dependent on the geometry and scanning conditions. The simulations show sensitivity mostly to the first nanometers of the sample and underline the importance of scanning near the sample and being careful with mechanical anharmonicities on the tip oscillation. They also help to determine the influence of oscillation amplitude and demodulation harmonic.
我们模拟了无孔径近场光学成像，并获得了用于弹性散射的结构化衬底的相位和幅度扫描结果。三维麦克斯韦方程组的求解不涉及近似，并且我们考虑了大尺寸的探针和衬底、强相互作用、干涉检测以及高次谐波的解调。这种建模朝着定量模拟迈出了重要一步，并为研究每个相关实验参数的单独影响提供了诱人的可能性。我们通常会获得探针与金内含物相互作用的高度局域化特征，叠加在缓慢变化的背景信号上。这两种贡献的相对重要性以及可实现的横向分辨率强烈依赖于几何形状和扫描条件。模拟结果表明，其灵敏度主要集中在样品的最初几纳米，并强调了在样品附近扫描以及小心探针振荡的机械非谐性的重要性。它们还有助于确定振荡幅度和解调谐波的影响。
