Theoretical proposal for actively manipulating optical differential operation in the quasi-PT symmetric structure

Optical differential operation is an important scheme for image edge detection due to its advantages of high efficiency, real time and low consumption. In this paper, the actively manipulating optical differential operation is proposed in a quasi-PT-symmetric structure containing graphene, and applied to realize edge imaging with tunable contrast. It is found that there are abrupt changes of the in-plane shift and transverse shift in the photonic spin Hall effect at the Fermi energy of 0.4 eV, where the quasi-exceptional points exist according to the degeneracy analysis of scattering matrix eigenvalues. Based on the photonic spin Hall effect near the quasi-exceptional points, we design the optical differential operation whose spatial transfer function is actively manipulated by changing the external electric field to adjust the Fermi energy of graphene. Finally, the edge imaging with different contrast can also be achieved when the optical differential operation is applied to image processing. The actively manipulating optical differential operation opens up new possibilities in microscopic imaging and smart driving.