Study Of Optical Transmission And Field Localization In Hybrid Plasmonic Waveguide Structure

Nano-optical waveguide is one of the most important components in ultrahigh integrated photonic devices. So far, various kinds of nano-optical waveguides have been proposed including dielectric waveguide, photonic crystal waveguide and plasmonic waveguide. Moreover, the optical nano-cavity can be realized by introducing the structure defects in the nano-optical waveguide. The optical nano-cavity is not only important to a lot of study areas such as the enhancement of light-metter interaction, the nano laser and so on but also one of the basic components of the integrated optical circuits. The main disadvantages in current nano-cavities are complicated structure, large size, difficult in fabricating and large mode volume etc. On the basis of these problems in nanocavity, we have designed a kind of hybrid plasmonic(HP) waveguide possessing small mode volume, high quality factor and easy to fabricate on the platform of the silicon on insulator(SOI) in this thesis. We have further optimized its size and studied its properties as a sensor.We have derived the dispersion relation of the one dimensional HP waveguide by combining the transfer matrix method and the Maxwell equations. Using the Finite Element Method(FEM) we have analyzed how the field distributions and the propagating length of the optical filed in the waveguide change as the size of the structure and the dielectric constant of the materials. The obtained results establish the foundation for the designing of the nano-cavity based on the HP waveguide in next step.On the basis of the properties of the optical fields in the HP waveguide,we have achieved the defect state by introducing the structure defect in the waveguide. The propagating characteristics and the field localization of a two dimensional model have been investigated by using the software COMSOL Multiphysics. To obtain the smallest mode volume, we have optimized the geometric parameters of the waveguide to find its corresponding optimum size.Then we have extended the HP waveguide to a three dimensional structure and further studied how the size of the defect, the material and the number of the periods affect the propagating characteristics of the optical waves in the waveguide. Taking advantages of the deep sub-wavelength confinement and the low loss of the HP waveguide, we have designed a nano-cavity whose mode volume and the Purcell factor are 0.005 mm3 and 3750 respectively. We have numerically studied the propagating properties of the optical wave when changing the refractive index of the dielectric layer and inserting a small metallic strip at the position of the defect. It is found that the HP waveguide has both the high Purcell factor and the fine sensing characteristics.The results shown in this thesis are useful in optimization design of the plasmonic waveguide and may find their applications in ultrahigh integrated optical circuits.