  Coordinate transformation is applied to design an all-dielectric device for
Extraordinary Transmission (ET) in a single sub-wavelength slit. The proposed
device has a broadband feature and can be applied from microwave to visible
frequency bands. Finite-Difference Time-Domain (FDTD) simulations are used to
verify the device's performance. The results show that significantly increased
transmission is achieved through the sub-wavelength aperture from 4 GHz to 8
GHz when the device is applied. In contrast with previously reported systems,
the frequency sensitivity of the new device is very low.
