Near-field focusing by a photonic crystal concave mirror

We have studied the electric-field distribution in the photonic crystal (PC) concave mirror. This was done numerically and was verified in experiment. The field mapping in our experiments was performed using the Slater's perturbation technique which was modified for nonresonant structures. The PC consists of a planar array of dielectric rods with a trapezoidal depression that forms the concave mirror. At the midgap frequency of the first stopband of the underlying photonic crystal, the mirror allows focusing to a subwavelength spot size of 0.2 lambda x0.2 lambda. The intensity is enhanced by 16 times at the focal point, as compared with the incident wave.