A Novel Design of Photonic Crystal Lens based on Negative Refractive Index

In this study a concave lens based on two dimensional photonic crystal platform with negative refractive index is presented. The proposed lens is employed as a spot-size converter to facilitate coupling of the light from a single mode fibre with a large spot-size area into photonic crystal waveguide with a very small spot-size area, even smaller than the operating wavelength. Optimisation of the lens and its integration with the single mode fibre and photonic crystal waveguide into a single optical chip was performed by employing 2D Finite-Difference Time-Domain (FDTD). A significant reduction of the optical chip dimensions and high coupling efficiency have been achieved by optimizing each device (the lens and the photonic crystal waveguide).