Study On The Principle Of Optical Circular Polarizer With Metallic Helical Metamaterials And Its Optimal Design

With the development of modern society, as an important polarizing component of optical field, the circular polarizer is required increasing performance. Traditional methods to obtain circular polarization have narrow bandwidth and are difficult to integrate. So it is important to optimize the design of circular polarizers.In 2009, the German J. K. Gansel et al first obtained the circularly polarized light with the electromagnetic metal spiral metamaterial. However, their study of circular polarizer is limited to the single spiral structure. We know that the structure of metallic helical circular polarizers has a great influence on its working performance. Therefore in order to gain circular polarizer with more excellent performance through the optimization of structural design of metal spiral circular polarizer. This paper has studied the following three parts:Firstly, we studied and analyzed the working principle of metallic helical circular polarizer. The interaction between metallic helical wire grid and the electromagnetic wave is very complicated. Based on helical antenna theory, we obtained the principle of selecting circular polarization to the metallic helical circular polarizer, through analyzing the excitation and the response process of metallic helical spiral grid. In addition, we provided the qualitative analysis of the reasons that metallic helical circular polarizer has wideband frequency response.And then, we studied the relationship between the structural parameters of metallic helical spiral grid and the working performance of circular polarizer. Using numerical simulation method, respectively we changed helix diameter, number of turns, helix pitch, spacing of constructed unit and the diameter of the helix to find their difference in the operating bandwidth and average extinction ratio of the device. At the same time, we summed up the change in the relationship between them.Finally, we proposed some other metallic helical structures as the optimization of circular polarizer. The optimization design of the helical circular polarizers includes metal N helical structure and tapered spiral metal structure. On the basis of the studies on the working principle and structural parameters, we proposed a circular polarizer with metallic N helix structure. We studied the optical performance of metallic double, three, four-helix structure. Their optical performances are different. However, compared to the single-helix metallic circular polarizer, their working performances, such as the operating bandwidth and average extinction ratio, have improve within a certain range. In addition, we also proposed a tapered helix metamaterials as improved circular polarizers. This structure is obtained by gradually decreasing the radius of metallic helix. The circular polarizers with tapered helix metamaterials extend the operating bandwidth and improve average extinction ratio of device.This paper studies the relationship between circular polarizer and the structure parameters of metal spiral, which provides guidance and direction for the optimization of metallic helix circular polarizer. In addition, metallic N-helix circular polarizer and tapered metallic helix circular polarizer improve the performance of device.