Design of two-dimensional photonic crystal structure based in all-angle negative refractive effect for application in focusing systems

A design of a polarisation independent focusing system of electromagnetic waves in a two-dimensional photonic crystal (PC) is proposed and numerically demonstrated by using the finite-difference time-domain method. We have shown that by the careful selection of both the refractive index of the high index material and the air cylinder radius, a complete all-angle negative refraction can be obtained for both the transverse electric (TE) and the transverse magnetic (TM) polarisations. We have demonstrated that the proposed PC structures can focus either the TE or the TM or both TE and TM polarised waves with sub-wavelength resolution. In addition, a significant improvement of the image resolution has been presented