Subwavelength drains designed for mirror-closed dielectric lenses

Mirror-closed dielectric lenses such as Maxwell's fisheye lens have been recently discussed to have unique light focusing capacity. The key issue for this lens is to make a perfect deep subwavelength drain which is able to absorb the entire wavefronts emitted by the source. In this work the authors proposed two methods to solve this problem and designed small size drains using time reversed scattering and transformation optics. At the image position, deep subwavelength focusing spots were achieved in a closed dielectric-embedded lens by these drains. The transformed drain could work at arbitrary wavelength and polarization. Our results showed the critical role of an attenuating drain in the imaging process of a Maxwell fisheye lens and gave technical approaches for their implementation. The general methods developed here may serve to design other interesting electromagnetic devices. (paper)