We present a general method for designing XUV aperiodic multilayer mirrors that can mimic a given target spectrum, specifically, the spectral transmission of an XUV optical system. The method is based on minimizing a merit function and using fidelity parameters that quantify the matching of the multilayer reflectivity spectrum with that of the target spectrum. To assess the feasibility of fabricating such a system, we show how to reduce the layer-to-layer thickness variations throughout the aperiodic layer stack. We demonstrate the design method using an example of an EUV optical system composed of 12 identical Mo/Si multilayer mirrors having a reflectivity peak at 13.5 nm. We found that the target spectrum can be mimicked with high fidelity either with a single reflection at an aperiodic multilayer mirror combined with standard absorbing filters or, if required, with two subsequent reflections at a mimic mirror. These examples demonstrate the applicability for metrology at XUV sources, including spectrally proper source imaging. Because our approach is of general applicability, the process can be used to mimic any other narrowband, single-peaked target spectrum in the XUV region.

中文翻译：

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反射型非周期性多层滤光片，用于XUV光源的计量。

我们提出了一种设计XUV非周期性多层反射镜的通用方法，该方法可以模仿给定的目标光谱，特别是XUV光学系统的光谱透射率。该方法基于最小化优值函数并使用保真度参数来量化多层反射率光谱与目标光谱的匹配度。为了评估制造这种系统的可行性，我们展示了如何减少整个非周期性层堆的层间厚度变化。我们使用一个由12个相同的Mo / Si多层反射镜组成的EUV光学系统示例演示设计方法，该反射镜在13.5 nm处具有反射率峰值。我们发现目标光谱可以通过高保真度模拟，或者在非周期性多层反射镜上与标准吸收滤光片组合使用一次反射，或者在需要时在模拟反射镜上进行两次后续反射。这些示例说明了在XUV光源（包括光谱正确的光源成像）上进行计量的适用性。由于我们的方法具有普遍适用性，因此该过程可用于模拟XUV区域中的任何其他窄带单峰目标光谱。