Design And Study Of Surface Plasmonic Superstructure For Circular Polarization Analyzer

In environment such as fog and mist with strong scattering, image resolutions can be enhanced by detecting the Stokes parameters that represents optical polarization state. Distinguishing left-handed circular polarization(LCP) state from right-handed circular polarization(RCP) state is one of the most difficult techniques in optical polarization state detection. Resolutions of polarized light imaging are mainly depend on how small the sensors can be. Recently, researchers are using techniques such as manipulating the transportation of Surface Plasmon Polaritons(SPP), Spin-Hall effect of Light and chiral metamaterials to develop circular polarization analyzers. This dissertation studies the electromagnetic responses of split-spiral rings, PbSi2-multiplane superstructure and three-dimensional(3D) chiral-superstructures, which are on the basis of the studies by former researchers.The near field transmission spectra of the designed split-spiral rings are calculated using finite element method(FEM). The circular dichroism of the split-spiral ring is observed. The extinction ratio of LCP and RCP is higher than 15 at the wavelength around 850 nm when the number of the rings is 4. Finally, the designed structure is fabricated using techniques of vacuum coating and Focused Ion Beam(FIB).The permittivity of PbSi2 at the wavelength in [1300, 2600]nm is quite similar to Au at the wavelength in [550,850]nm. The far-field transmission spectra of the proposed PbSi2-multiplane superstructure are obtained using Finite Difference Time Domain(FDTD) technique. Circular dichroism is observed at the wavelength in [1600, 2600]nm, which can further be developed as semiconductor integrated circular polarization analyzers.Two new types of 3D chiral superstructures are designed according to the principle of electromagnetic induced transparency(EIT). Similarly, the transmission spectra of LCP and RCP are calculated using FDTD. Due to the coupling between bright and dark mode, EIT-like spectra are observed around the frequency of the single spiral resonances. After transmitting from these two structures, according to the calculation of electric field in the time domain, the time delay between the incident LCP and RCP Gaussian pulses are observed to be 8.3ns and 4.9ns respectively. Finally, the support structures are fabricated using the cutting edge techniques of 3D printing, which are assembled with twisted Ag wires using UV curing adhesives.