Theory Study On Surface Plasmon-induced Transparency And Slow Light Effect In MIM Waveguides

With the diversified development requirements of optical communication deivces, Surface plasmon polaritons(SPPs) has attracted the extensive attention these years due to its strong localization and transmissivity characteristics. SPPs is a kind of electromagnetic wave formed by the interaction between external photons and free electrons, which propagates along the surface of metal and strongly bonded to the metal and dielectric interface. It breaks the limits of diffraction and makes it possible to manipulate light field in subwavelength scale. Based on the theory of SPPs, a kind of typical structure, metal-insulator-metal(MIM) has been studied.The main research work includes the following aspects:1. A kind of MIM waveguide with multiple coupled-metal-cavities(CMC) is designed based on SPPs theory. The dispersive relation of SPPs modes in the CMC with different number is studied by mode solver of COMSOL Multiphysics simulations. The mode distribution of MIM waveguide with different number is given. When the adjacent two modes become close enough, plasmon-induced-transparencies(PIT) will be induced by destructive interference. We conclude the relationship between the number of CMC and PIT window. Based on early work, a kind of multichannel add-drop coupler is designed which can be applied into multichannel wavelength division multiplexer.2. The filter characteristic of the MIM waveguide with two detuned square ring resonators is studied. The two detuned resonances are established by two square ring resonators with different lengths. PIT can be explained by a well-defined phase coupling. Through the method of finite element, we find that for third order detuned resonances, there is one PIT; for second-order detuned resonances, there are one, two, or three PIT, depending on the detuning degree between the two square ring resonators. Electromagnetic simulation is carried out to calculate the PIT transmission spectrum and electromagnetic field distribution. The proposed configurations may find significant applications in wavelength division demultiplexing systems and sensors devices.3. Transmission characteristics and transmission line model of MIM waveguide with a stub modified by cuts is proposed. Conducted by finite element method, the three resonance wavelengths between 750 nm to 1800 nm are studied. The results show that the wavelengths of transmission dip vary with the position of the cuts and form the zigzag lines. A Transmission line model is also presented, and compared with simulation result to verify its validity. The differences is caused by the additional phase from reflection of stub. The physical mechanism under the evolution of the transmission-dip wavelengths is discussed by examining magnetic and electric field distributions. Set MIM waveguide with detuned stubs modified by cuts and its dutuned degree can be adjusted by placed the cuts on different positions. With the increasement of detuned degree of two stubs, the PIT window becomes larger and causes a red shift. We also set the corresponding transmission line model of this detuned stubs MIM waveguide. Compared with the simulation result, the validity of model is proved.