Research On Optical Transmission In Micro-nano Periodic Structures

Surface plasmons (SPs) are waves that propagate along the surface of a conductor. By altering the structure of a metal’s surface, the properties of surface plasmons include the dispersion relation, modes and the coupling effect and so on can be tailored. In this paper, using the Finite-Difference Time Domain method (FDTD), we study the basic physical properties of surface plasmon resonance in metallic nanostructures.Our main work is listed below:1. We study the transmission properties of a Z-shaped metallic slit array with bars by using the2D-FDTD method. It is found that the bar adjusts surface resonance peak and FP resonance peak easily. When the width of the bar changes, all peaks red-shift and increase. These behaviors can be explained by F-P cavity theory. The variation of bar length causes the coupled mode’s red shift while FP resonance peak keeps the same. The bar’s variation helps us prove the FP-SPP mode theory. Most importantly, obvious dip emerges when the bar deviates from central line and gradually close to above slit’s edge. These behaviors can be attributed to the phase resonance. The bar’s slight variation leads to tremendous change of transmission; this may be useful for making optical switch or filter.2. The structures are made up by tip-coupled pattern, back-coupled pattern and tip-back-coupled pattern. The transmission spectra of tip-coupled pattern and back-coupled pattern are alike, Fano resonance and EIT-like window can be observed in these two patterns. Especially, back-coupled pattern exhibits a striking result. The transmission spectrum of tip-back-coupled pattern exhibits quadruple Fano resonance. What’more, similar behaviors appear in these three structures by changing coupling length.3. Compare the difference of transmission spectra between C-shaped split-ring resonator (SRR) and U-shaped resonator (SRR). Effects of oriention and coupled length on transmission are discussed. We find that transmission spectra are not the same in different orientations and that only dipole resonance red-shift drastically. Different properties that result from different combination patterns can be used to make photonic devices.