基于散射SNOM的超分辨成像光场的检测方法研究

Super resolution imaging light filed is the near field light that highly localized around the surface of super resolution imaging device. It can only exist on the surface of the devices, and decay extreme fast as it go outs of the surface. Highly localized properties of the light field lead to hard detection by conventional optical lens. There exist two methods of near field light detection at present, one is via photoresist exposure process, and the other is via conventional SNOM technique. But both two approach can`t make the accurate detection of near field light available. We will use scattering SNOM to investigate the light distribution on the image plane of the super resolution imaging device. The basic principle of the interaction between probe tip and near filed light will be comprehensively studied. The influence of probe tip`s morphology and properties on the detection of the near field via the tip`s perturbation to evanescent wave and the suppression of the background light noise are going to be investigated to obtain the accurate near field light intensity, phase change and polarization. The near field light distribution and metal film surface properties of the exact position will be detected in-situ and synchronously using scattering SNOM. The correlation between metal film surface properties and image quality of the device will be comprehensively studied.

超分辨成像光场是指局域在超分辨成像器件表面的倏逝波光场信息，它只能够存在于器件的表面，离开表面以后强度迅速衰减，导致传统的成像检测方法无法使用。目前，倏逝波成像光场的检测一般采用光刻胶记录的方法或利用开孔式扫描近场光学显微镜探测的方法。前者受到激发波长、曝光等因素影响，导致光场检测准确性、稳定性降低，后者则主要受到光学分辨力极限和低光传输效率的制约。本项目基于散射式扫描近场光学显微镜Scattering-SNOM(Scattering-Scanning Near-field Optical Microscopy)研究超分辨成像光场的强度分布、相位变换以及偏振性质等参数的表征分析方法，建立一种能够直接对超分辨成像光场进行检测的新方法。通过研究近场探测散射源与倏逝场相互作用机理，分析散射源对倏逝场本身造成的扭变程度，探究近场光学信号的有效提取和准确识别，为超分辨成像器件的研究提供有效表征方法。

超分辨成像光场总是局域在器件表面，离开表面后光场迅速衰减，传统光学方法很难直接检测这种倏逝光场。本项目基于散射式扫描近场光学显微镜（Scattering-SNOM），研究了一种能够直接对倏逝光场性质进行检测的方法。首先设计了基于等离子体的亚波长平板聚焦透镜结构，并且使用有限元方法分析了平板透镜的狭缝周期、狭缝填充介质对聚焦效果的影响规律。同时，还讨论了入射光偏振态与聚焦效果间的关联，发现TM偏振光入射，并且平板透镜填充SiO2后可获得良好的聚焦效果。通过优化设计，获得了一组聚焦效果较好时的平板透镜结构参数，并利用相应的微纳加工手段加工了等离子体平板透镜样品。为了更好地讨论填充介质对相位调控的影响，设计加工了杨氏双缝结构并采用传统光学成像方法进行了相位偏移探测，发现填充介质确实能有效地进行相位偏移调控，并且实验结果与理论设计基本符合，这为等离子体平板透镜的聚焦能力提供了可行性保证。接下来，利用Scattering-SNOM对等离子体平板透镜样品进行表征，采用Two-Pass扫描方式测量了等离子体平板透镜的聚焦效果，并与计算的聚焦结果进行对比，发现测量的聚焦焦斑与理论计算的大致一致，这表明本项目提出的基于Scattering-SNOM的近场测量方法是有效的。虽然聚焦焦斑的实验测量值与理论计算值存在一定差异，但在容忍范围之内。本项目提出的方法有望广泛应用于近场测量领域中。