Effects of Coherent versus Incoherent Illumination and Imaging Setup on Experimental Measurements of Scattering Amplitudes in Metamaterials,ACS Photonics

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Effects of Coherent versus Incoherent Illumination and Imaging Setup on Experimental Measurements of Scattering Amplitudes in Metamaterials
ACS Photonics ( IF 6.5 ) Pub Date : 2021-06-01 , DOI: 10.1021/acsphotonics.1c00599
Sotiris Droulias ₁ , Costas M. Soukoulis _{1,

2} , Thomas Koschny ₂

Affiliation

The characterization of metamaterials typically depends on the determination of scattering parameters like transmittance and reflectance, and comparison with numerical models. While, numerically, coherent plane wave scattering amplitudes for infinite perfectly periodic samples are readily accessible, experimental measurements necessarily involve scattering of possibly incoherent optical probes with finite-size illumination spots on finite sample surfaces that need to serve as a proxy for the true plane wave scattering amplitudes. In some situations, but not always, this difference can lead to substantially different observed scattering spectra. Here, we investigate and analyze the observable effects on the measured scattering spectra originating from coherent versus incoherent optical probes, finite illumination spot size, magnifying imaging systems, as well as beam shaping optical elements. We discuss the relation of all the above to the wave vector content of the illumination and the sample’s spatial dispersion properties, and we show that they can result in qualitatively significant deviations of observed scattering spectra from true plane wave scattering, which needs to be taken into account to really understand experiments and allow a faithful comparison with simulations.

中文翻译：

相干与非相干照明和成像装置对超材料散射幅度实验测量的影响

超材料的表征通常取决于散射参数（如透射率和反射率）的确定，以及与数值模型的比较。虽然在数值上，无限完美周期性样品的相干平面波散射幅度很容易获得，但实验测量必然涉及可能不相干的光学探针的散射，有限样品表面上的有限尺寸照明点需要作为真实平面波的代理散射幅度。在某些情况下，但并非总是如此，这种差异会导致观察到的散射光谱大不相同。在这里，我们研究和分析了对来自相干与非相干光学探头、有限照明光斑尺寸、放大成像系统，以及光束整形光学元件。我们讨论了上述所有与照明的波矢量内容和样品的空间色散特性之间的关系，并且我们表明它们会导致观察到的散射光谱与真正的平面波散射在质量上存在显着偏差，这需要考虑帐户以真正理解实验并允许与模拟进行忠实比较。

更新日期：2021-06-17

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