Study of Broadband Negative Refraction with Vertically Stacked Hyperbolic Metamaterials

Abstract

Negative refraction has generated much interest recently with its unprecedented optical phenomenon. However, a broadband negative refraction has been challenging because they mainly involve optical resonances. This thesis reports the achievement for broadband negative refraction in the visible spectrum by using vertically-stacked metal-dielectric multilayer structures. Since this structure has different signs of parallel and vertical effective permittivity, it exploits the characteristics of the constituent metal and dielectric materials according to the direction. Moreover, it does not require resonance to achieve negative refraction. With the calculation of Poynting vector that indicates the direction of energy flow, broadband negative refraction is numerically demonstrated in wavelength from 270 to 1300 nm. Compared to conventional metamaterials such as split ring resonators and horizontally-stacked multilayer structures that employ resonances, the vertically-stacked multilayer structure has a broader range of working wavelength including visible range, with higher transmittance. The thesis also reports a variety of material combinations with broad working wavelength. The broadband negative refraction metamaterial helps to manipulate light in an extraordinary way and may make a breakthrough in optical applications such as hyperlens, super-resolution imaging, and invisibility cloaks.