Research On Electromagnetic Force And Torque Of Microwave And Light Wave

Electromagnetic force and electromagnetic torque is an important and fundamental issue in electrodynamics. Scientists have made intensive studies of the electromagnetic force and electromagnetic torque in the static fields or quasi-static fields during the second industrial revolution. The results have become the theoretical basics for many subjects such as electrical machinery, electrical appliances and electromagnetic measurement, etc. Nowadays the information society poses more innovation demands on the research of the problems about electromagnetic force and torque exerted by microwave and light wave. Supported partially by the Natural Science Foundation of China (NSFC) under Grant No. 50577029 and 50777023, this thesis investigates electromagnetic force and torque in microwave and light wave fields.The problem of electromagnetic force and torque of microwave and light wave is a new issue. There is no mature model available and the relevant studies were very few. A classification for the interaction force between microwave or light wave and medium is performed in this thesis. And the analysis of electromagnetic force exerted on basic types of medium was provided. This thesis sum up general conclusion, and proposes the conception of equivalent sources. All the problems about electromagnetic force can be analyzed by this method. It can explain all electromagnetic force experienced by all kinds of medium. There were two types' models which can produce time-average nonzero force in plane wave. One is free sources model and the other is bound sources model. After the charge wave and current wave were defined, the condition for nonzero electromagnetic force on those waves was deduced. A PN junction model is studied for its electromagnetic force. The synchronization condition is discussed theoretically. The electromagnetic force on conducting medium in evanescent fields is computed. The enhancement effect of force was revealed in this thesis.As the bound sources model, in view of existing fact that the optical pressure is very small, the way to enhance electromagnetic force by principle of localized fields is carried out in one-dimensional photonic crystal with defect. The in-detail-calculations of electromagnetic force in this structure demonstrated that the normal force on defect layer can be infinite theoretically. At the same time, tangential force can also increase. Only in oblique incidence and on the lossy medium the tangential force can exist.For electromagnetic torque, light-induced rotation is always the hot research topics. In that case, the angular momentum carried by light was used for spinning the objects. But the torque is really small. Only for micro-particles this torque is big enough to operate, and then the light-induce rotation for those particles has been investigated extensively. About large electromagnetic torque induced by the plane wave there were few reports. This thesis introduce anisotropic slab into one-dimensional photonic crystal with defect. Through the Berreman 4×4 matrix, the characteristics of fields in finite one dimensional photonic crystal with defect that is consisted of anisotropic medium are calculated. The thesis demonstrated that the anisotropic layer would be rotated by electromagnetic torque besides normal force. And the torque will not change by the rotation of the anisotropic layers. This can form twist model. If defect mode is evoked in that one-dimensional photonic crystal, the electromagnetic torque was enhanced. Compared with the torque experienced by an isolated anisotropic layer under the same light, the electromagnetic torque increased in the order of 12. Another advantage of this model is no losses theoretically.The research of the electromagnetic force and torque is expanded from low frequency to microwave and light wave in this thesis. Two types of model are to enhance the electromagnetic force and torque. The models of charge wave and current wave are defined. The studies in this thesis would enrich or supplement the theory analysis and calculations for electromagnetic force. And provide the basis for further revealing electromagnetic force in two-dimensional or three-dimensional photonic crystal with defect, and expand their more applications.