提出了一种可同时达到高对比度和高反射率的对称金属包覆结构。由于导波层的厚度是亚毫米量级，使该结构可容纳一系列共振模。利用四层波导菲涅耳公式，详细分析了耦合金属层的厚度对耦合效率的影响，给出了反射光达到最大对比度时耦合金属层厚度的最优值，并从物理的角度解释了这种现象产生的原因是对称金属包覆结构中的辐射损耗和本征损耗共同作用的结果。实验测量了对称金属包覆结构中反射光的干涉效应。结果表明，对称金属包覆结构可以大大增强反射光的干涉条纹中明、暗光线的对比度，同时光入射到对称金属包覆结构中的耦合效率可接近100%。这将有助于研究高对比度高反射率薄膜和基于对称金属包覆结构的传感器。

A double metal-cladding structure which can achieve high contrast approaching unity and high-reflectivity is proposed. This double metal-cladding structure with sub-millimeter scale can accommodate a series of resonant modes. Using the Fresnel reflection formula of the four layers, the relationship between coupling efficiency and thickness of upper metal layer is analyzed and the optimum value of thickness of upper metal layer can also be obtained. It is also found that such optimum value is closely related to the intrinsic and radiative damping. The interference fringes of reflected beam and coupling efficiency on double metal-cladding structure were observed experimentally. Experimental results showed that high contrast approaching unity can be observed from interference fringes and coupling efficiency can reach nearly 100% on double metal-cladding structure. It is useful for the investigation of high contrast high reflectivity films and the sensors based on double metal-cladding structure.