The circular polarizers were mostly made of meta-atom based chiral metamaterials (CMMs). Here we propose an ultra-thin metallic grating based circular polarizer, which can convert any polarization into circular polarization. The circular polarizer consists of two layers: an ultra-thin metallic grating embedded in the substrate and a silicon grating on the substrate surface. The ultra-thin metallic grating, which is thinner than the skin depth and was shown to hold anomalous resonant reflection for transverse magnetic (TM) wave, functions as a quarter-wave plate. We show that the ultra-thin metallic grating based quarter-wave plate can transmit circular polarized wave when the incident linear polarized wave is oriented properly. The silicon grating acts as a linear polarizer which restricts the polarization of the light that reaches the metallic grating. Unlike some of the CMMs, our structure is independent of the incident polarization state. Moreover, the fabrication of our circular polarizer is easier than other double-layer-CMMs, in which the relative position between the two layers must be precisely controlled. Our structure can find its application integrated photonic devices.
Surface plasmons have been widely investigated in many fields due to the unique property. ATR (attenuated totalreflection)
is the common method to excite surface plasmons. We derive the Fano-type analysis to present the
reflection spectrum of ATR configuration derived from the three-layer Fresnel reflection equation, which are
asymmetric curves resulted from interference between direct reflectance and surface plasmons leaky radiation. In the
fitting progress, we obtain the relationship between surface plasmons leaky radiation and metal thickness. When the
metal thickness is greater than 25nm, surface plasmons leaky radiation rate is less than 0.07. We also compare the ATR
and grating coupler excitement mechanism, which provide a reference to evaluate their application.
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