Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC)slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice ofair holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directionsof the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negativerefractive-index material. The light radiated from a point source can form a subwavelength image spotthrough the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can beachieved for the incident wave with its incident angle within a certain range.
Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.
