Study On Photonic Topological Corner State And Its Application

Behind the colorful butterfly wings are the unique physical properties of photonic crystals.Photonic crystals are artificial microstructures of materials with different refractive indices arranged periodically in space.It is widely used in the design and manufacture of miniaturized and high-performance micro-nano photonic devices due to its two characteristics of photonic band gap and photonic localization,and finally realize large-scale “All-optical network”.However,the performance of the device is always affected by the scattering caused by the inevitable impurities in manufacturing,which is solved by the introduction of topology into optical field,a novel photonic integrated circuit platform based on topological photonics.Topological photonics has attracted much attention due to the great potential of waveguides for immunity to disturbances.However,compared with the current research on topology-protected waveguides,the development of micro-cavity based on topological photonics is relatively slow.The concept of high order topological insulator provides a way of thinking about this problem,which is characterized by its support for topological states with lower dimensions than itself:for example,a 0 dimensional topological state will be localized at the corner of a second order topological insulator structure.High-order optical topological insulator can introduce stable cavity modes into the system.Common micro cavities are very sensitive to defects,and small structural changes can result in detuning of resonant frequency and mode volume.Topology protection will provide more stable mode frequency and stronger mode restriction.When defects are introduced into the structure,the frequency of the microcavity protected by topology will not change.This paper mainly studies the optical topological corner state and its application.We have studied the second-order optical topological insulator composed of the all-dielectric Kagome lattice structure.By adjusting the intensity of the intra-cell coupling and the inter-cell coupling,we have obtained two structures with different topological properties.At the interface between the two structures,we found that the electric field distribution is concentrated in the corner.Interestingly,we also found two other corner states with different field distributions that are different from the traditional corner states.In order to further verify the physical mechanism of this corner state,we design a new detuned Kagome lattice structure to verify and analyze the influence of the far-field action on the corner state.In addition,we designed a waveguide-cavity coupling structure on the basis of the above-mentioned corner state to realize the electromagnetically induced transparency effect,and studied its cause and regulation.These results may expand our understanding of the higher-order corner modes in a more general framework.The relevant research results can be used to design topological The nature of micro-nano photonic devices,such as optical storage,optical switches,optical buffers.It is expected to make the "all-optical network" come one day earlier.