In this paper, we propose a tunable graded index (GRIN) photonic crystals (PCs) based on liquid crystals (LCs).

The GRIN PC with index gradient on the order of Δn=0.16 is realized using the symmetry reduced unit element in two-dimensional PCs without modifying the dielectric filling fraction or cell size dimensions.

The simulation results show that the proposed structure has capability of moderate light focusing over a wide range of incident frequencies, making it suitable for applications such as flat lenses and couplers.

Light manipulation with such photonic medium is explored and a new approach for active tuning of focal distance is proposed.

By applying an external static electric field to LCs, their refractive index and thus, the effective refractive index of the whole GRIN PC will be changed.

This property can be used for designing an electro–optic GRIN PC-based flat lens with a tunable focal point. Future optical systems may have benefit from such tunable GRIN lenses.

Therefore, we believe that our paper will attract to the attention of the readers of Optics Communications.