Study On The Direct Detection Of Circular Polarization Using Surface Plasmon Resonance

Polarized light can be decomposed into right-handed circular polarization and left-handed circular polarization. It also can be decomposed into circular polarization and linear polarization. In many applications such as the radar target recognition, we need to detect the circular polarization from the polarized light. At this moment, surface plasmon resonance provides a new way for direct detection of circular polarization. Incident light irradiates at the interface of metal and medium and forms a kind of evanescent wave, namely the surface plasmon. The specific metal structure can interact with incident light forming local resonance correspondingly. This resonace is not only related to the shape and size of metal structure, it is also influenced by material of metal and dielectric. The metal spiral structure can respond to circular polarization light. The performance of this spiral structure is decided by the efficiency of surface plasmons, the crosstalk between units and different responce between circular polarization light and linear polarization light. This paper mainly include the following works:Firstly, this paper studies on the efficiency of surface plasmon excitation. By simulation we analyze the excitation characteristics of the metal-metal structure and metal-medium-metal structure. To reduce the crosstalk betweenthe units, we use two metal-medium-metal modules with different size (i.e. different phase of resonance) to make the surface plasmon to be excited only in one direction.In order to detect directly circular polarization, we use a left-handed screw structure and a right-handed spiral structure as a detection unit. Due to the spiral structure on the right hand shows left circularly polarized light response and no response to left-handed circularly polarized light, the right spiral structure is just the reverse. If the incident light is linear polarized light, the spiral structure of the response at the same situation. Therefore, we only need to test the net difference between the two structures'response in one detection unit. Base upon the optimization of the efficiency and sigle direction of excitation, the detection contrast of incident circularly polarized and linear polarized light can reach more than 20 times.