A novel electro-optical switch is proposed and investigated using the transfer matrix method (TMM) and three-dimensional finite-difference time-domain (3D FDTD) analysis at the near-infrared range. The structure is made of a defect at the middle of a one-dimensional photonic crystal. The defect consists of two anisotropic graphene (AG) sheets separated by a dielectric layer. As a result, a sharp transmission peak with a high quality factor of 5000 appears at the wavelength of 1552.4 nm where light is trapped by the defect. When an external voltage is applied across the AG sheets, their chemical potentials shift in such a way that the trapped photons are absorbed and the switch changes to ON state. According to the presented results, a high extinction ratio of 14.26 dB with a very low insertion loss of 0.18 dB are obtained. The required switching voltage and energy consumption are as low as 4.68 V and 226 fJ/bit, respectively. The 3 dB bandwidth is also calculated to be as high as 17.5 GHz, which makes our proposed switch promising for high speed optical systems.
In this article, a new tunable absorber and polarizer using one-dimensional anisotropic graphene photonic crystal (1D AGPC) is proposed for terahertz applications. The optical properties of the 1D AGPC structure is obtained through the transfer matrix method (TMM) calculations. In our design, a single defect layer is introduced in the 1D AGPC structure to increase its absorption. The absorption coefficient is further modified by optimizing the AGPC parameters such as the number of photonic crystal periods, the defect layer thickness, and the chemical potential of graphene. The modified structure can provide perfect absorption with a narrow bandwidth of 0.05 THz. On the other hand, considering the anisotropic optical properties of graphene, polarization dependence of the absorption coefficient is investigated. This feature of the structure can be employed to realize a tunable terahertz polarizer by adjusting incident angle at θ 0 = 80°. In this way, high tunable polarization extinction ratio of 6.1 dB to 11.63 dB with respectively very narrow bandwidth of 0.031 THz to 0.023 THz are obtained. The maximum insertion losses within the tunable frequency range are as low as 0.023 dB and 0.031 dB. Hence, our design may have potential applications in narrow-band optoelectronic devices at the terahertz frequency range.
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