Reconfigurable Topological Photonic Crystal And Application In Biology

Photonic crystal?PhCs?is a kind of artificial crystal material with bandgap,which has been developed rapidly in recent years.It is widely used and valuable in optical waveguide and optical communication..However,it causes great losses due to the strong backscattering in light transmission.The observation of topological edge states?TESs?revolutionized our understanding of scattering and propagation of electromagnetic?EM?waves.Supported by topological robustness,the TES at the interface between trivial and non-trivial insulators was not reflected from the structural disorders and imperfections.Therefore,the concept of topology was introduced into the field of photonics,and topological PhCs were designed.The topological photonic crystals were demonstrated to obtain remarkable one-way propagation of the TES,having the advantages of lossless scattering,dense integration,and high fabrication tolerance over conventional PhCs.However,the dynamic controlling of TES are rarely explored.Therefore,we proposed the idea of controlling the transmission characteristics by changing the background refractive index,designed the reconfigurable topological PhCs.On account of many anisotropic biomolecules existing in life as liquid crystals state and having different refractive index,we applied topological photonic crystal to the detection of biological liquid crystal in the visible band.In the thesis we specifically designed C₆ topological photonic crystal.Then we calculated and analyzed the energy band and electric field distribution with finite element method.Through the simulation of COMSOL Multiphysics,we realized the topological PhCs with unidirectional propagation of light along the interface of trivial and non-trivial photonic edge states.Next,we designed a reconfigurable topological PhCs with anisotropic liquid crystal material as the background,and realized two transmission modes of light scattering and controllable propagation under different alignment conditions of liquid crystal,which achieved the switching and tuning of topological photonic crystal to light propagation.Finally,based on the biological phenomenon of liquid crystal,we designed topological photonic crystal in visible band.We proposed the method of detecting biological liquid crystal molecules with the reconfigurability of topological photonic crystal.Then we simulated the two modes of light transmission with the background of DNA solutions under the liquid and liquid crystal states.Therefore we demonstrated the application of topological photonic crystals in biology field specifically.