Asymmetric optical transmission through silver film with a hyperbolic air hole

Asymmetric optical transmission is one of the most important functionalities in modern optical communication systems. However, it has been impeded due to the low transmission ratio of forward transmittance to the backward transmission ratio. This paper is a continuation of the paper by Peng et al. [Opt. Express22, 17546 (2014)OPEXFF1094-408710.1364/OE.22.017546]. It was found that the guided mode reflects remarkably on the bottom of a conical air hole. A guided mode reaching the bottom of a conical air hole is the major factor leading to the asymmetric optical transmission effect. It reminded us that the asymmetric optical transmission effect of a structure having a much steeper inner wall would be better. Thus, we proposed silver film with a hyperbolic air hole (HAH), of which the transmission ratio can be as high as 17.5 at a proper wavelength. Through analysis, as we expected, the mechanism is the steep inner wall of the silver film HAH really can inhibit guided-mode reflection.