The Study And Design Of Spin-wave Focusing Device Based On Optical Principles

The study of spin waves is a hot research area in spintronics.Spin waves have broad application prospects in information storage and processing.Efficient spin wave front regulation is the key foundation for information processing using spin waves.Spin waves are similar to light waves and have wave characteristics,and other similar physical laws;for example,spin wave refraction at the interface can be described by the extended Snell's law of refraction.The focus of wavefront is an important research content in wavefront regulation,which has a wide range of applications in device processing and imaging.In the visible light band,the lens can be used to focus the light wave well.According to the theory of diffraction,the focal plane of the focusing device is considered to be the spatial spectrum surface(or two-dimensional Fourier transform),and then the concept of spatial filtering is introduced to develop into information optics Branch.In view of the fact that focusing devices in the visible light band have been widely studied,according to the consistency of the wave research methods,the design scheme of the focusing device in the optical band can also be well used in the focusing device of the spin wave.In this paper,the design schemes of Fresnel zone plate,Fresnel lens,Maxwell fisheye lens and anamorphic Luneburg lens in optics are introduced into spin wave.And through the simulation of micro-magnetic software to study the characteristics of its spin wave focusing.The main contents are as follows:The first part studies the spin wave focusing device based on excitation source phase adjustment,which mainly includes spin wave Fresnel zone plate and spin wave Fresnel lens.Both of these lenses are designed with the initial phase of the excitation source to match the phase distribution of the Fresnel zone plate or Fresnel lens in optics,and the focusing effect on the spin wave is studied.The simulation results show that the two devices have obvious focusing effect on the spin wave.By setting different phase distributions,the focal length can be adjusted,and the simulation results are basically consistent with the theoretically designed focal length changes.In addition,the focusing characteristics of the spin wave Fresnel lens can also be dynamically adjusted by applying an external magnetic field.The simulation results also show that the spin wave Fresnel zone lens can achieve the dual focus of the spin wave.The second part studies the spin wave lens based on the graded refractive index distribution,which mainly includes the spin wave fisheye lens and the anamorphic spin wave Luneburg lens.By setting concentric circles with different refractive indexes(saturation magnetization)on the ferromagnetic film,the gradient distribution characteristics of the refractive index were successfully constructed.The simulation results show that both types of lenses can effectively focus the spin wave.With the spin-wave fisheye lens,the focal point characteristics can be changed by changing the parameter refractive index n,distribution constant a,and applied magnetic field.For the anamorphic spin wave Luneburg lens,this paper mainly chooses the bifocal Luneburg lens.Numerical simulation shows that the anamorphic spin wave Luneburg lens can achieve the designed bifocal focusing function.The research of this kind of spin wave focusing device provides new research content and direction for spin wave regulation,and also provides new ideas for the design of spin wave focusing device.