Research on Uniderectional Non Reflection Characteristics of Photonic Crystals Based on PT Symmetry

In this paper, a parity-time (PT) symmetric one-dimensional photonic crystal structure with double defects and double symmetric periods is proposed. By setting the same defect layer in the periodic structure on both sides, the symmetry broken pase in the structure on both sides appears at the same frequency point. This structure presents a one-way non-reflection characteristic at a frequency point in the near-infrared band. By adjusting the thickness of the defect layer, the position and value of the reflection peak can be flexibly changed. It is found that with the increase of the thickness of the defect layer, the performance of the uniderection reflection point decreases and moves to the high frequency direction. Peiod number has no effect on the position of the reflection peak, when $\boldsymbol{N}=\mathbf{6}$ , the maximum forward reflection peak is obtained; the change of the incident angle will make the uniderection reflection point move back and forth within a certain range. After adjustment, the reflectance of forward incident light of the structure can reach 47, while the reflectance of reverse incident light is only $\mathbf{3.9}\times \mathbf{10}^{-\mathbf{5}}$ . This structure realizes high-performance one-way reflection transmission, which can be used for stealth or optical isolation, etc.