This paper theoretically shows that nearly perfect absorption can be achieved by adjusting the period numbers of the two graphene based photonic crystals surrounding a lithium niobate (LiNbO3) layer. Since LiNbO3 is an electro-optical (EO) material with voltage dependent refractive index and high EO coefficient, peak wavelength tunability of absorption has been revealed. Our investigations show that the relation between the peak wavelength and applied external voltage is linear, so that the peak wavelength moves toward shorter wavelengths by increasing the applied external voltage. Moreover, it is possible to achieve multi-peak by varying the thickness of LiNbO3 defect layer. Finally, we discuss the possibility of control of the absorption via controllable parameter (chemical potential) of the graphene. The results indicate that for a given structure, i.e, definite period numbers surrounding the LNO layer, the enhanced absorption can be achieved, by adjusting the chemical potential.
