Optical metamaterial for polarization control

We present the design, characterization, and modeling of a specific optical metamaterial, and employ it to manipulate the light polarizations at optical frequencies. Experimental results reveal that the maximum polarization conversion efficiency, i.e., the energy portion converted from $s$ to $p$ polarization after reflection, can be as high as 96% at the wavelength of $\sim 685\text{nm}$. Simulations and analytical results, which are in reasonable agreements with the experimental results, reveal that the underlying physics are governed by the particular electric and magnetic resonances in the optical metamaterial.

Figure 1

(Color online) (a) Side-view geometry of the optical metamaterial studied in this paper. (b) Top-view SEM picture of a part of the experimental sample. (c) Scheme of the experimental setup. Here, BS denotes beam splitter, CH confocal hole, LP linear polarizer, OL objective lens, and SM spectrometer. (d) The coordinate system adopted in this paper.

Figure 2

(Color online) Relative reflectivity as functions of wavelength for normally incident waves with polarizations $\vec{E}\parallel \widehat{x}$ (solid symbols) and $\vec{E}\parallel \widehat{y}$ (open symbols), obtained by (a) measurements and (b) FDTD simulations. (c) Reflection phase difference $\Delta {\phi }_{yx}$ as a function of wavelength calculated by the FDTD simulations.

Figure 3

(Color online) (a) Measured polarization-conserved relative reflectivity (${\left|r_{ss}\right|}^2$, solid symbols) and polarization-converted relative reflectivity (${\left|r_{sp}\right|}^2$, open symbols) as functions of wavelength. (b) The calculated PCR as a function of wavelength using the experimental data. (c) The PCR spectra as functions of wavelength obtained by numerical simulations and theoretical analysis.

Figure 4

(Color online) Retrieved effective parameters of the metamaterial, (a) ${\tilde{\epsilon }}_x$, (b) ${\tilde{\epsilon }}_y$, (c) ${\tilde{\mu }}_y$, and (d) ${\tilde{\mu }}_x$, as functions of wavelength; Optical parameters (e) ${\tilde{\epsilon }}_x$, (f) ${\tilde{\epsilon }}_y$, (g) ${\tilde{\mu }}_y$, and (h) ${\tilde{\mu }}_x$ as functions of wavelength, calculated with formulas (3).

Figure 5

(Color online) (a) The PCR spectrum as a function of wavelength obtained by theoretical analysis. (b) Real and imaginary parts of $Z_x{Z}_y$ as functions of wavelength.