Numerical Study On The Manipulation Of Terahertz Waves By Structured Black Phosphorus And Artificial Photonic Crystals

Metamaterials are artificial composites whose electromagnetic properties can break through the limitations of natural materials.Their structures and electromagnetic properties can be designed freely according to our needs.In recent years,due to the rapid development of new materials and micro-nano processing technology,researchers have developed more and more metamaterials with special electromagnetic properties.Although terahertz radiation exists widely in nature,few traditional materials have obvious response to terahertz waves.Metamaterials have electromagnetic properties that traditional materials do not possess,so the combination of terahertz and metamaterials has naturally become a research hotspot in the development of terahertz technology.Based on some theories of metamaterials and terahertz waves,this work presents a detailed study on the response of black phosphorus metamaterials and metal column photonic crystals in the terahertz regime.The details are as follows:1.We reviewed the background and basic knowledge of this subject,summarized the development history and recent research progress of terahertz technology,and introduced metamaterials and photonic crystals briefly.In order to explain the response mechanism of metamaterials,two theoretical models,coupled harmonic oscillator model and equivalent medium model,are introduced.Next,we derived the dispersion relation of surface plasmon polaritons,and introduced several important characteristic parameters.We also briefly introduced the surface states of photonic crystals and their resonant modes.2.Surface plasmon polaritons of black phosphorus?BP?metamaterials were investigated.Surface plasmon polaritons can be divided into localized surface plasmons and propagative surface plasmons.In this study,we successfully excited localized surface plasmons by designing black phosphorus into nano-sized strip structures.In order to observe electric-field localization and light confinement resulted from the BP nanostrips easily,we employed a reflective structure to enhance the light-matter interaction.Next,we investigated the influence of the structural parameters of the proposed BP metamaterial unit cell on its plasmon behavior.We also analyzed the F-P effect,the coupling between elements,and the effect of black phosphorus duty cycle on overall results.3.Topological surface states of graphene-like photonic crystals were further presented.In this study,we have designed graphene-like photonic crystals by aligning metal cylinders into hexagonal honeycomb structures.We used COMSOL Multiphysics software to calculate its energy band structure,and then we broke the Dirac point of the original energy band structure by breaking the C₆ symmetry of the photonic crystal to form the energy band gap.Finally,we combined two kinds of photonic crystals with different topological properties to construct an interface channel,realizing the transmission of topological surface state.