Research Of Beam Manipulation Using Metamaterials

Metamaterials are artificial electromagnetic materials which can achieve specific permittivityεand permeabilityμas desired. They have many extraordinary properties and unprecedented applications, and gradually becomes an international hotspot. Compared with conventional materials, a greater advantage of the metamaterials is that we can design materials by the need of devices, which provide more convenience for manipulating electromagnetic fields and designing optical devices.In this paper, we modulate beams using metamaterials based on transformation optics. The specific work we carry out is as follows:First, we study the modulation of the beamwidth using metamaterials. A scheme of obtaining a line beam from a beam with finite width is proposed based on transformation optics, and the constitutive tensors of metamaterials are obtained. And the good performance of the beam modulation is verified through full-wave numerical simulations based on the finite element method. Such electromagnetic wave-manipulating devices provide alternative ways either to expand or to compress the electromagnetic beamwidth, or to focus or collimate gaussian beams, and the line beam with very high energy density in the beam center will find applications in enhancing nonlinear optical effects or other areas. The devices we propose will also be applied to optical elements or other potential electromagnetic devices.Second, we manipulate the phase of the beams and obtain the optical orbital angular momentum. The beams with orbital angular momentum may be valuable in particle manipulation and quantum communication. To generate orbital angular momentum, we need to achieve the helical phase of beams. Therefore, according to the transformation optics, we get the constitutive tensors of metamaterials. By these analytical results, we implement the full-wave simulations based on the finite element method, and the results show that the helical phase of the incident gaussian beams are generated, and the Laguerre-Gaussian beams are obtained. Our results provide a new way for producing beams with orbital angular momentum.