Investigation Of All-dielectric High-Q Resonant Structures Based On Coupled-mode Theory

High-Q resonant structures are widely utilized in sensing,narrow-band filtering and high-frequency modulation and other fields.By using the ultra-narrow spectral characteristics,it can be achieved for the detection of specific materials or elements by identifying the unique spectral components and filtering higher harmonics and other functions.However,the design of high-quality factor structure still suffers from the problems of large overall loss,large volume,and usability to realize the electrical adjustment.In this thesis,the traveling wave structure and the standing wave structure are studied,respectively.The existing problems of high-quality-factor resonant structure are discussed and solved with different ideas and forms of realization with the help of new principles,new ideas and new structures.A series of studies on the structures of traveling wave and standing wave and the theory of coupled mode theory are studied.For the standing wave,the coupling rule of one to three units are proposed.Physical models corresponding to different situations under different coupling conditions are studied to clarify the similarities and differences between them.The models proposed in this part are able to explain the physical concepts of all the following designs.As for the traveling wave,the principles of photonic crystal band gap and defect mode are analyzed,and the coupling effect between two transmission lines is studied.Based on the analysis of the physical model of the coupled structure of the standing wave and traveling wave,the theoretical foundation for the subsequent design is established.For the design of high-Q resonant structure based on the standing wave,to solve the problem of large loss of standing wave structure,a novel high-quality factor structure based on Aulter-Townes effect of coupled field is proposed.Firstly,the electromagnetic response characteristics of traditional metal-dielectric-metal structure and all-dielectric resonators are analyzed.The characteristics and effects of the resonant and coupling effects are explored,and the effect of the coupling effect is clarified.By analyzing a series of coupling models,a suitable structure for exciting Aulter-Townes effect is chosen.The coupling field is combined with the Aulter-Townes effect by changing the boundary conditions of the electromagnetic field.The structure is able to reduce the dielectric loss by the coupling field without changing existing advantages.That will provide new possibilities for the design of high-Q optical devices with a new method.On one hand,for the design of the high-Q resonant structure based on traveling wave,the idea of utilizing graphene sheets in one-dimensional photonic crystal structure is proposed.Electronically controlled one-dimensional photonic crystal structure is realized by using the characteristics of graphene with the change of bias voltage.By extracting the constitutive parameters of the graphene sheets and combining the transmission matrix of the metamaterial,a calculation method of graphene transport matrix is proposed.And the spectral characteristics of one-dimensional photonic crystals loaded with a certain number of layers of graphene sheets are deduced by this method.At the same time,by changing the electromagnetic and physical properties of the graphene,the red-shift/blue-shift properties of the whole structure are analyzed once the graphene properties are changed.The change of the defect mode of the photonic crystal structure is analyzed emphatically.Meanwhile,considering the mechanical effect produced by the defect mode,and using the Maxwell stress tensor surface integral,a theoretical model of an active terahertz electromagnetic force generator is proposed.By means of the graphene sheets,an electrical-controlled mechanics is realized.The effectiveness of the method is proved by numerical simulation.In addition,the coupling effect between two transmission lines based on 2-dimensional photonic crystals are also discussed,which is a beforehand research of the coupling between traveling wave structures and the standing wave structures.Finally,the Ph C is coupled with the coupled-mode theory.The Ph C structure is used to reduce the dimension of the prototype.Meanwhile,the quality factor is increased by the coupling mode,Which lays a foundation for the further application of the coupling mode effect.Overall,in this thesis,the design theory of a new high-Q resonant structure is studied from the two aspects of traveling wave structure and standing wave structure,respectively.Theoretical modeling and numerical simulation are utilized for verifying the efficiency of the proposed models.The problems of large overall loss,large volume,and usability to realize the electrical adjustment mentioned above have been solved with the novel structure based on Aulter-Townes effect.Moreover,the structure is simple and easy for optimizing,which is both suitable for theoretical analysis and fabrication.