Circular phase-dichroism (CPD) has been suggested for the characterization of chiral metasurfaces in supplementing the conventional circular dichroism (CD). Conventional CD probes the bulk properties while the CPD, reported recently in 2D chiral metasurfaces using an air–gap Fabry–Perot setup, is based on the surface properties. Here we propose and demonstrate a robust birefringent interference approach to obtain the CPD by replacing the air–gap with a uniaxial birefringent material in which interference is realized by the difference in the refractive indexes for the ordinary and extraordinary components of the material. We measure the transmission phases of metasurfaces fabricated on birefringent sapphire substrates and obtain clear CPDs for chiral metasurfaces but vanishing for achiral metasurfaces. Importantly, our approach can be applied to metasurfaces fabricated on nonbirefringent substrates by add-on birefringent materials. We confirm our results by a Jones matrix method using data obtained from full-wave simulations, and good agreements with experiments are obtained.

中文翻译：

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利用双折射干涉的手性元表面的圆相二色性

在补充常规的圆二色性（CD）中，已经提出了圆相二色性（CPD）来表征手性元表面。常规的CD探测了整体性质，而最近使用气隙法布里-珀罗装置在2D手性超表面上报道的CPD是基于表面性质的。在这里，我们提出并演示了一种稳健的双折射干涉方法，该方法通过用单轴双折射材料代替气隙来获得CPD，在该单轴双折射材料中，干涉是通过该材料的常规和非常规组分的折射率差异实现的。我们测量在双折射蓝宝石衬底上制造的超颖表面的透射相，并获得用于手性超颖表面的清晰CPD，但对于非手性超颖表面则消失。重要的，我们的方法可以应用于通过添加双折射材料在非双折射基板上制造的超颖表面。我们使用从全波模拟获得的数据通过琼斯矩阵方法确认了我们的结果，并与实验取得了良好的一致性。