Design And Research Of Hybrid Surface Plasmonic Waveguides With Gain Medium

With the rapid development of integrated optics, surface plasmons have attracted considerable attention in the field of nano-photonic technology because of its unique properties and wide application prospects. Surface plasmons polaritons(SPPs) are electromagnetic surface waves tightly confined at the metal-dielectric interfaces which are formed by the interaction of the external electromagnetic field and the free electrons at the metal surface, exhibiting the characteristics of high localization and near-field enhancement. Plasmonic waveguides based on SPPs can break the diffraction limit that conventional dielectric waveguides cannot overcome to achieve subwavelength optical confinement and transmission, contributing to the miniaturization and high integration of photonic devices. In many types of plasmonic waveguides, hybrid plasmonic waveguides show the unique advantage that both strong optical confinement and low propagation loss can be achieved simultaneously. In this paper, by introducing the suitable optical gain medium into the hybrid plasmonic structure, we design two new types of hybrid plasmonic waveguides and investigate the properties of the proposed structures by using the finite element method, which provides a theoretical basis and design idea for the development of a new generation of nano-photonic integrated devices such as deep-subwavelength-scale plasmonic nanolasers.The main work of this paper is as follows:(1) Based on the development and application prospects of surface plasmons, the basic theories about surface plasmons and surface plasmonic waveguides are introduced,the characteristics and advantages of hybrid plasmonic waveguides are mainly analyzed,and the optical waveguide materials and the numerical calculation method — — Finite Element Method are described, providing some theoretical basis for the following design and investigation of novel waveguide structures.(2) We design a cylindrical nanowire based hybrid plasmonic waveguide with gain medium. We investigate the electric field distribution of the fundamental hybrid plasmonic mode and the effect of the geometric parameters on the modal properties by using thefinite element method at the visible light wavelength and calculate the gain threshold for plasmonic nanolaser applications. The results reveal that the structure can realize low-loss propagation at the deep subwavelength scale. By optimizing the geometric parameters of the structure, a minimal threshold is obtained while maintaining the capacity of ultra-deep subwavelength mode confinement. The proposed structure has lower threshold compared with the previous coupled nanowire pairs based hybrid plasmonic structure with the same geometric parameters.(3) A hybrid plasmonic waveguide with metal-semiconductor ribs is proposed. We numerically simulate the electric field distribution of the fundamental hybrid plasmonic mode at the infrared wavelength and analyze the dependence of the modal properties and the gain threshold on the geometric parameters by using the finite element method. The simulation results indicate that the structure enables ultra-deep subwavelength mode confinement with low propagation loss and low threshold. By optimizing the geometric parameters, the best properties are achieved for the proposed waveguide. Compared to the previously studied hybrid plasmonic waveguide with a metal plate on the top, tighter mode confinement and lower propagation loss are simultaneously achieved for the structure with the same geometric parameters. The designed structure can be used as a low-threshold nanolaser and has promising potential for applications in high-density photonic integrated systems and optoelectronic integrated circuits.