Research On Propagation Properties Of Nanoresonators Coupled Metal-waveguide Structures Based On Plasmon-induced Transmission Effect

Surface plasmon polaritons(SPPs),which are the type of transverse electromagnetic waves,propagate along the interface between metal and dielectric material.SPPs have attracted tremendous attention for breaking the diffraction limitation.The design and application of photonic devices based on SPPs is currently one of research hotspot at home and abroad.By using the finite element method(FEM),some coupled sub-length waveguide nano-structures based on plasmon-induced transparency and absoption effect were designed.The main research works of this thesis are listed as follows:Firstly,the propagating characteristics of SPPs in the structure composed of the metal-insulator-mental waveguides and side-coupled rectangle resonator were investigated and the law of the transmission dips shifting with structure parameter changed was found out.The mechanism of formation and evolution of plasmon-induced transparency(PIT)in two side-coupled rectangle resonators structure was analyzed.The PIT effect can be divided into two categories according to two different physical pictures.In one picture,PIT is achieved by a well-defined phase coupling that can be established between detuned resonances.In the other picture,PIT arises from the normal-mode splitting of a low-Q(radiative)resonance induced by its coupling with a high-Q(dark)resonance.Then,three and four side-coupled rectangle resonators structures were proposed.The tunable PIT phenomenon in proposed PIT structures at visible light and communication band is investigated.The simulation results showed that for three rectangle resonators structure,not only can we manipulate each single PIT window,but also the double PIT windows simultaneously by adjusting only one of the geometrical parameters of them;for four rectangle resonators structure,by changing the widths,the lengths and the refractive index of three cavities synchronously,we would realize treble PIT peaks and induce an off-to-on PIT optical response.Secondly,the transmission characteristics of a structure composed of the MIM waveguides and single ring resonator at vi,sible light and communication band were studied.The influence of the radius or the refractive index of the ring on the transmission spectrum was investigated.The structure composed of the MIM waveguides and dual-ring resonators was proposed and the propagating characteristics of SPPs in the structure were investigated.The simulation results showed that an off-to-on plasmon-induced adsoption(PIA)response could be achieved by varying the separate between two rings,the radius or the refractive index of the rings.And what's more,the transmission characteristics of a structure composed of the MIM plasmonic waveguide and two concentric nanorings were investigated.Outer and inner nanorings work respectively as bright and dark resonators,so the extreme destructive interference between two resonators gives rise to the distinct PIA effect in the second mode.Finally,the structure consists of dual side-coupled circular ring resonators and two waveguides with a baffle was proposed.When the baffle changed from the transparent medium to the noble metal,PIA-to-PIT effect was obtained.When the baffle is silver and its length is 20nm,for the two shunt-wound rings system,an on-to-off PIA optical response could be achieved by adjusting the radius or the refractive index of the lower ring.For the series-wound rings system and the concentric rings system,it is difficult to achieve the on-to-off PIA optical response by adjusting the structural parameters of these two systems although there are PIA windows in the transmission spectra.Proposed structures may play a new platform for developing slow-and fast-light techniques and find important applications in nano-integrated optical circuits for optical switching and storage,highly performance filter.