Negative refractive behaviors of 2D triangular-lattice photonic crystals by structure of SiO2/TiO2 layers

In this paper, we propose a two-dimensional (2-D) triangular lattice photonic crystal plate by close-packed SiO2/ TiO2 layers with the stacking mode of ABABABA. By using the finite-difference time-domain (FDTD) method, negative refraction of a single Gaussian beam incident plate with different angles are respectively demonstrated; clear image spots of a point source with normalized frequency ω=0.3605(2πc/a) vertical incident media plate are obtained in the image plane. It can be found that the imaging properties are as same as the isotropic homogeneous medium with refractive index n=-1. The measurement results show that when the distance between the image and the upper surface of the sample V is 5.12a, 3.09a and 1.15a, the distance between the source and the lower surface of the sample U is a, 3a and 5a, respectively. This means that the sum of U and V is mostly equal to the thickness of the plate L and the negative effect of near-perfect lens is realized. This proposed structure with negative refraction properties may have great applications for the design of photonic crystal focusing devices.

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