| The law of reflection of light is the most fundamental optical phenomenon of light.It points out the relationship between the incident and reflected rays,and also explains how light propagates at the interface of different materials.With further research,it is found that the reflected beam at the interface will have a certain shift with the incident beam,where the shift along the incident direction is called transverse Goos-H?nchen（GH）shift and the shift perpendicular to the incident direction is called lateral Imbert Fedorov（IF）shift.The beam shift is essentially a result of the angular momentum transformation and conservation of the beam spin angular momentum and orbital angular momentum during the reflection-transmission process.Natural dielectric hyperbolic crystals have unique and excellent optical properties,which not only promote the development of surface optics,near-field optics and nano-optics,but also are an ideal material system for exploring new surface optics and electromagnetic properties and an important model for theoretical studies.In recent years,there has been great interest in the spatial shift of the incident beam interacting with the surface of the medium,especially in hyperbolic materials to study their properties.Compared with natural uniaxial hyperbolic materials,natural biaxial hyperbolic materials possess in-plane various anisotropies and have a large local effect on the spin angular momentum and orbital angular momentum of the beam,which are rarely studied and are the focus of this paper.The following is the main research content.1.Based on the classical electromagnetic theory and the transmission matrix（TMM）method,the transmission matrices of the reflected and incident beams on the surface of a natural biaxial hyperbolic material thin film structure under different polarization beam incidence are calculated,and the stable phase method is applied to calculate the transverse GH shift and longitudinal IF shift on the surface of the structure with a crystal as an example.The reflectance of the reflected beam from the surface is calculated for different structural parameters.The results show that the shift maximum of 4.2λ0 is reached at a frequency of 955.1 cm-1,when the reflectivity reaches 0.4.The IF shift on the surface of the structure also varies with the thickness of the film,peaking at the boundary of the hyperbolic frequency interval at about 2.4λ0.2.Based on the angular spectrum theory,the spatial shift of the reflected beam from the surface of the thin film/semi-infinite h BN crystal structure is calculated by applying the TMM method.It is found that the GH shift of the new structure is greatly enhanced up to 86λ0.The GH shift also exhibits an optical F-P resonance with increasing film thickness.These results provide a new way for the modulation of the beam shift,thus offering the possibility of developing novel nano-optical devices. |
