Confinement Of Electromagnetic Waves In Two-dimensional Structures In The Frame Of Trasformation Optics

Transformation Optics has been an important subject ever since it was introduced in 2006. Based on the form-invariance of Maxwell’s equations under space distortion, Transformation Optics is a powerful tool in controlling electromagnetic waves and designing optical devices conveniently and efficiently. What’s more, it offers a brand new thought of understanding physical problems from geometrical perspectives. With the help of newly introduced metamaterials, people have experimentally achieved several functional devices such as invisibility cloak, optical lens and so on. Furthermore, the basic concept of Transformation Optics can also be applied to other physical fields, like acoustics, quantum mechanics, thermodynamics and even subjects of controlling fluid flows.In this work, under the frame of Transformation Optics, we investigate two kinds of devices that can confine electromagnetic waves efficiently and try to apply the concept of Transformation Optics to designing subwavelength optical microcavities.First, we introduce a folded geometry in the deep subwavelength optical cavity introduced in 2008. With the help of folded geometry we successfully introduce a complementary media inside the perfect cavity and manage to separate the confined energy to certain regions with different radius. Analytical calculations are applied to work out the constitutive parameters and numerical simulations are taken to verify the feature of the transformation device. This work may provide a new strategy to confine light and rearrange them in a two-dimensional subwavelength structure.Second, we propose a method of cavity design with the help of Transformation Optics. The proposed transformation design aims at prolong the optical path inside the cavity to confine light to some extent using azimuthal transformation. Analytical calculations are taken to find proper cavity modes inside the structure and numerical simulations are also introduced to verify the analytical solutions. With the help of simulations we also calculate the quality factors of some single modes; a series of modes with high Q are illustrated. It turns out that the proposed transformation has the ability of confining light effectively to its vicinity. Hope the method applied would be useful in designing optical cavities.To sum up, we have studied the functional devices applying Transformation Optics that confine light and place the confined energy at certain areas. We can see from the works that Transformation Optics is indeed a powerful tool in designing optical devices and understanding physical problems. These works are inspiring in the upcoming applications on Transformation Optics.