Abstract In this work, we show that unequal-arm two-beam interferometers, for example, single-pass Mach–Zehnder interferometer or double-pass Michelson interferometer, illuminated with coherent point source (spherical wave front) or coherent line source (cylindrical wave front), unambiguously determine the sign of the phase shift. Theoretical consideration shows that a pattern with finite diameters of interference fringes is asymmetric with respect to the sign of the optical path difference (OPD) or phase shift (PS). In a short arm of the interferometer, the light passing through the layer of medium, characterized by positive OPD (positive PS), leads to the decrease of the diameter of interference fringe. The layer of the medium with negative OPD increases the diameter of inference fringe. When placing an object in the long arm of the interferometer, the contrary situation is observed. For variants with a coherent linear source, the above results relate to the distances between strait fringes of the same order. Experiment demonstrates that the positive optical path length of a conventional material can be compensated in air by a layer of metamaterial with a negative optical path length located at a distance significantly longer than the wavelength of light.

中文翻译：

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用于表征具有负光程长度的亚波长层的两光束干涉测量法

摘要 在这项工作中，我们展示了不等臂双光束干涉仪，例如单程马赫-曾德尔干涉仪或双程迈克尔逊干涉仪，用相干点源（球面波前）或相干线源（圆柱波）照明。前），明确确定相移的符号。理论考虑表明，具有有限直径干涉条纹的图案关于光程差 (OPD) 或相移 (PS) 的符号是不对称的。在干涉仪的短臂中，光穿过介质层，其特征是正OPD（正PS），导致干涉条纹直径减小。具有负OPD的介质层增加了干涉条纹的直径。当将物体放在干涉仪的长臂中时，观察到相反的情况。对于具有相干线性源的变体，上述结果与同阶海峡条纹之间的距离有关。实验表明，传统材料的正光路长度可以在空气中通过一层具有负光路长度的超材料来补偿，该超材料位于明显长于光波长的距离处。