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Abstract Focusing by the designed negative Luneburg lens which is based on graded annular photonic crystals (GAPCs) are studied in this paper. The GAPCs are composed of ring-shaped silicon pillars in a hexagonal lattice. The gradient of refractive index is achieved by modifying the radii of inner holes. The effective negative refractive index is analyzed based on the photonic band structures and verified by the simulation of negative refraction in APCs flat lens. Numerical simulation results show that a 0.6λ focusing spot can be realized by our designed Luneburg lens and it has the potential to be utilized in photonic integrated circuits. Highlights • We designed a negative Luneburg lens based on the graded annular photonic crystals (GAPCs) by ring-shaped silicon pillars. • The gradient of refractive index is achieved by modifying radii of the inner hole that has been analyzed and verified. • A 0.6λ focusing and coupling by GAPCs Luneburg lens show the potential to be utilized in photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Negative refraction in a hexagonal two-dimensional (2D) annular photonic crystal (APC) has been studied. The photonic band structure and equal frequency contours of the designed APC are analyzed using the plane wave expansion method, and the subwavelength imaging is simulated using finite-difference time-domain method. Numerical simulation results indicate that negative refraction and subwavelength imaging can be realized in the designed APC. The resolution of the designed APC slab is better than the radiation wavelength. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, superlens realized by a two-dimensional (2D) triangular lattices graded photonic crystal (GPC) was studied. The graded photonic crystal (GPC) was obtained by varying the radius in each row so that its effective refractive index changes along the transverse direction. Plane wave expansion (PWE) method and finite-difference time-domain (FDTD) were adopted to show that negative refraction and superlens can be realized in the designed graded photonic crystal. [Copyright &y& Elsevier]