![]() ![]() However, it is only recently that reflection phase is obtained over a wide range in the optical wavelengths using a simple Fabry Perot (FP) interference technique, and a cross-polarization method. The reflection phase of a metasurface can be obtained using standard interference method for single or discrete wavelength(s). Thus, it is highly desirable to characterize chiral metasurfaces, especially metallic based metasurfaces, by probing the surface properties like reflection or more sensitively the reflection phase. Moreover, current metasurfaces are mostly metallic based. This size dependence could reduce its sensitivity for highly absorptive materials, e.g. However, as CD probes the bulk properties of the chiral materials, the CD signal thus depends on the sample size. Chiral property is conventionally characterized, other than the polarization rotation, by the circular dichroism (CD) defined as the difference in the absorption/transmission of different circularly polarized, left- and right-handed, incident light. This drawback is circumvented by the use of micro/nanometer-thick chiral metasurfaces in which large optical activities (polarization rotation and circular dichroism) are possible, ,, ,, ,, ,, ,, ,, ,, ,. Optical devices made of natural chiral materials have weak optical activities and thus they are usually very bulky in order to achieve noticeable chiral effects. On the contrary, chiral materials exhibit novel optical activities such that the handedness of incident light can be modified or transformed. Ordinary materials are not sensitive to the handedness of incident light and thus they are labeled as achiral. Recent review articles on metasurfaces summarize well the fundamentals and potential applications of metasurfaces, ,. ![]() due to its simplicity in fabrication and large-scale production, and thus has drawn much interest recently. On the other hand, two-dimensional (2D) metasurface, being a subset of metamaterials, has high potential for device applications such as beam deflectors, , metalenses, optical vortex plates, , cloaking surfaces, metaholograms, , etc. Due to the advances in nanotechnologies, metamaterials can now be fabricated to achieve the above properties towards optical frequencies. Novel properties such as negative refraction, , superlens, and cloaking that are not feasible using natural materials can be realized because of the structural effects of metamaterials. ![]() Metamaterials are man-made structures with sizes much smaller than the wavelengths of interest. Our results demonstrate the potential applications of circular phase-dichroism in sensing and metasurface characterizations. The measured circular phase-dichroism is also crosschecked by conventional CD measurement of the transmitted light and by full-wave simulations. As a demonstration, we measure the reflection phase from planar chiral sawtooth metasurface for circularly polarized light in the visible range using a simple Fabry Perot interference technique. Here, we introduce a new approach termed as circular phase-dichroism that is based on the surface properties and is defined as the difference of the reflection phase for different circularly polarized incident lights in characterizing chiral media. Thus, CD probes the bulk properties of chiral media. The ability of chiral media to differentiate circularly polarized light is conventionally characterized by circular dichroism (CD) which is based on the difference in the absorption of the incident light for different polarizations. ![]()
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