The Cloaking Of Biomolecules In The Visible Region

Transformation optics(TO)has attracted much attention,arising from the fact that it can control the propagation of light based on coordinate transformations.In the last decade,people have devoted themselves to cloaking electromagnetic(EM)waves using TO devices,benefited from the rapid development of EM metamaterials(MMs).Although the progresses that have been made provide strong supports for this goal,the performance of cloak is still restrained since this coordinate transformation based cloaking approach requires highly anisotropic and inhomogeneous MMs that complicate the engineering implementation of TO in practical devices.The recent concept of surface-wave cloaks has in turns spawn a new research direction of “TO cloaks”,aiming at cloaking EM surface-waves at willing.The first approach follows the coordinate transformation method and thus requires anisotropy that leads to leaky waves producing radiation losses.The second approach adopts the carpet cloak method,but this approach is limited to a large size of cloak compared to the wavelength.Apart from this problem,some of these carpet surface-wave cloaks are unidirectional,limiting their practical applications.The third solution to the surface-wave cloak is an alternative surface-wave bending approach.While these designs show the advances to obtain isotropic and omnidirectional surface-wave cloaks that enable the curvature of a surface to be invisible,it only exhibits the cloaking phenomenon in the GHz region.Smoothly guiding light around a hidden object without disturbing the wave amplitude or phase is in great demand for optical and plasmonic devices.This paper first introduces the arc length method in optical transformation theory,analyzes and calculates the hemispherical,conical,parabolic,cosine and semi-ellipsoidal model structures.The normalized method is used to normalize the refractive index distribution in the model.For ease of calculation,the refractive index of the bottom plate is set to 1 to calculate the refractive index profile of the different models,and then uses the multi-physics simulation software(COMSOL Multiphysics)to determine the required model structure----semi-ellipsoid.Since the height of the semi-ellipsoid determines the distribution of the refractive index,so the height of the semi-ellipsoid is analyzed to determine its height.By optimizing the size of the model in the visible frequency band,the cloak device achieves surface wave perfect cloaking technology.In order to facilitate the application of the stealth technique in practice,the graded refractive index distribution is discretized by a layered method,hence hiding the object.According to the analysis of the arc length,it is concluded that the wavelength of the electromagnetic wave propagating in the semi-ellipsoidal structure has no relation to the refractive index in its structure.So the scope of application of the model can be extended to the visible spectrum,that is,in the visible frequency band at different wavelengths to achieve the same stealth effect.In the application of visible region,the device shows a good potential and experimental ability.It is noteworthy that,like the plasmonic cloak,the wave penetrates the cloak,and hence has the applications of noninvasive probing,cloaked sensors,and low-interference communications in the visible region.Because of the invisible size of the cloaking technology in the nano-scale,the cloaking nature of biomolecules has a natural superiority.And we give the stealth device on the ball,DNA molecules and protein structure of perfect invisible effect.