Electromagnetic Transverse Spin In Homogeneous Media

The spin angular momenta is an intrinsic property of electromagnetic fields,which can be used to control the propagation of electromagnetic waves,and hence can be widely applied in designing the microwave RF front-end,various photonic devices,and etc.Compared to the conventional longitudinal spins,the transversely spinning electromagnetic fields indicates the possibility of manipulating the on-chip propagation of EM waves,through those manmade structures which are commonly limited in the 2D plane that the chip lies in.Unfortunately,wave propagation with transversely spinning features used to be observed in confined systems,such as Surface plasmons polaritons,optical diffraction and imaging.It is obvious that these transverse spinning states can hardly be hold without those external confinements,which limits the study and potential applications in practical scenarios.It would be interesting and meaningful if the transversely spinning states can be stimulated in bulk media without any external confinement,so the potential applications can be further extended.In this thesis,by solving the Maxwell's equations with two typical constitutive relations,the transversely spinning states of electromagnetic fields are theoretically derived.In detail,theoretical analysis of bulk states in anisotropic media(or Gyrotropic media)and bianisotropic media(or artificial Metamaterials)are exhibited to possess transversely spinning feature,which makes up the basic interpretation of bulk states transverse spins in optics.The main content of this thesis contains:1?By consulting the characteristics of transversely spinning Surface plasmons polaritons,a mathematical mapping of transverse spin is established between evanescent waves and the bulk states in homogenous medium.Followingly,the main frame of the media's(which supports transverse spins in its interior)constitutive relations is obtained by the global symmetry analysis.As well,by solving source free Maxwell's equations,and the bulk's eigen-states are proven to show transversely spinning characteristics,for both the homogeneous bianisotropic media(or artificial Metamaterials)and the anisotropic media(or Gyrotropic media)cases.2?An artificial bianisotropic media block was constructed using the unbalanced split resonant ring(USRR,a particular metamaterial losing rotational symmetry).By analyzing the dispersion relations and propagation behavior of TM polarized modes,the link between magneto-electric coupling and the bulk's electromagnetic insulating effect is exhibited.Detailed analysis reveals that although the bianisotropic medium obeys the time reversal symmetry(so it is always topologically trivial),the spinning of EM fields can support optical insulating.In case two bulks with opposite spinning behaviors are placed together,the spinless edge states can be excited on the interface.Under the condition of zero refractive index,the propagation of the edge states can overcome structural scattering and nearly unidirectional transmission can be observed.3?The source free Maxwell's equation in Gyrotropic medium is fully solved,and the propagation behavior of electromagnetic waves in such kind medium is discussed.The inner relationship between the transversely spinning feature and the bulk media's cutting off characteristics are successfully established.It is demonstrated that the power flow of the transversely spinning waves is severely disturbed by the transversely spinning behavior.With broken time reversal symmetry,the wave propagation inside the Gyrotropic medium exhibit transversely spinning with stable spin angular momenta,regardless of the direction of the wave vector.Hence,it is evident that such a media can behave similar to the topological insulators in optics,and the bulk-edge correspondence is reasonably indicated.With computer-based simulations,we show the successful excitation of edge states,as well as the unidirectional propagation of EM waves.