## 4 Conclusions  
We demonstrate a new approach for retrieving the effective optical properties of the structured strips of a metamaterial grating. The simulations are performed for an effective grating, implying uniform anisotropic material, using the well-known RCW technique, which is modified to allow magnetic behavior and anisotropy. Notably this expands the relevance of the model to capturing properties for inclined illumination by capturing the anisotropy of the properties of the strips in contrast to the validity at normal incidence only of the effective layer model. Coupling experimental measurements of samples with inclined illumination in addition to normal incidence to a scattering software tool (MIST) allows us to model both inclined and normal incidence illumination and capture relevant diffracted orders. Providing the proper set of complex permittivity and permeability functions, a successful fit to the experimental data will occur. This retrieval method allows for capturing behavior in nonzero diffraction orders. Indeed, the diffraction features observed in the experiment and simulations in Figure 5 at 450 nm have been excluded from the retrieval results in Figure 11 due to the applied approach. Thus our method provides a more broadly relevant effective property extraction for use in applications of magnetic gratings. The coupling of experimental methods to the MIST package is additionally useful in that, once the optical parameters are obtained, one may probe the system via the same simulation environment in other ways to realize applications, such as waveguide-based biosensing, and to optimize grating performance by examining configuration changes. We believe a similar scheme can be useful for two-dimensional gratings [23], i.e., the so-called \"fishnet\" nanostructure, to obtain their effective unit parameters.  
**Acknowledgments:** [PERSON] acknowledges support of this work by Russian Ministry of Education and Science grant RFMEFIS8117X0026.  
**Author Contributions:** [PERSON], [PERSON] and [PERSON] conceived and designed the experiments; [PERSON], [PERSON], [PERSON] and [PERSON] performed experiments; [PERSON] extended the RCW theory to include magnetic susceptibility, as described in Appendix A, [PERSON] and [PERSON] performed numerical simulations. All authors contributed to overall data analysis and scientific discussions. [PERSON], [PERSON],  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **Advantages** & **Disadvantages** & **Limitations** \\ \hline \multirow{3}{*}{Effective Layer} & Well-known method; & \multirow{2}{*}{\
\begin{tabular}{c} Cannot be accurately \\ used for oblique \\ incidence \\ \end{tabular} } & Affected by diffraction, \\  & normal-incidence & & only wavelengths longer \\ \hline \multirow{3}{*}{Effective Strip} & Accounts for diffraction; & \multirow{3}{*}{
\begin{tabular}{c} May require additional \\ experimental setup \\ \end{tabular} } & Long wavelength \\  & & & approximation \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison between effective layer and strip methods for parameter retrieval.  
[PERSON], [PERSON] and [PERSON] wrote the manuscript with contributions from all authors. [PERSON] supervises the project.  
The authors declare no conflicts of interest.