Abstract
Here, we present blueprints for three types of ultra-thin beam splitters based on versatile fishnet metamaterial structures at the 1.55 μ m optical communication wavelength. The thicknesses of the designed polarizing beam splitter and partially polarizing beam splitter are 1/26 of the free-space wavelength, while the thickness of the non-polarizing beam splitter is 1/13 of the free-space wavelength. Numerical simulations show that, compared to other miniaturization approaches including popular dielectric metasurfaces, metal-based metamaterial approach can provide much thinner beam splitters with reasonable performance. Such beam splitters can enable miniaturization of conventional and advanced quantum photonic systems towards higher density, scalability, and functionality.
Highlights
A beam splitter is an important optical component used to split a beam of incident light at a desired ratio into two separate beams
The beam splitters can be typically classified into three kinds according to the input and output polarizations: polarizing beam splitter (PBS), partially polarizing beam splitter (PPBS)
non-polarizing beam splitter (NPBS) based on phase gradient dielectric metasurfaces was theoretically proposed at visible and near-infrared spectra with TiO2 nanopillars on a glass substrate and LiNbO3 nanocylinders on a fused quartz substrate [1,2], and experimentally realized with a 1-bit coding scheme [3] and tested with variable splitting ratios and broadband response [4] at THz frequencies using Si pillars on a Si substrate fabricated by combined photolithography and deep reactive ion etching
Summary
A beam splitter is an important optical component used to split a beam of incident light at a desired ratio into two separate beams. We present three types of ultra-thin beam splitters under different geometries of fishnet metamaterial structures (see Figure 1). These beam splitters are all designed to operate at the 1.55 μm wavelength, relevant to optical communication systems, where the absorption of glass material used in fiber is small. The reflectance and transmittance for the TE-polarized and TM-polarized light can be controlled in anisotropic fishnet metamaterial structures by changing primarily the wire widths and the periods along different directions as well as metal layer thickness. The filling ratio, the impedance mismatch and resultant reflectance and transmittance for different polarizations, can be controlled by the periods and metal layer thickness in the fishnet structure. In the regions close to the resonance frequency, the bulk skin depth technique in [27,28] can be useful in improving the efficiency
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