Regulation Of Bound States In The Continuum And Generation Of Vortex In Photonic Crystals

Photonic crystals refer to periodic dielectric structures with photonic band gap characteristics,and are typical periodic optical systems.Photonic crystals interact with light at sub wavelength scales,which can localize light at a certain frequency in the photonic crystal band gap.Bound states in the continuum(BIC)are states in which some frequencies are located within the radiation continuous domain but are not coupled to the radiation wave,and still remain localized.In photonic crystals,BIC is widely used in various fields such as biological optics,information optics,photonic integration and communication.The strong coupling between transition metal dichalcogenides(TMDs)excitons and optical resonators can control nanoscale light matter interactions.When photons are strongly coupled to TMDs excitons,a new type of boson exciton polaron is generated,which has a strong exciton energy.As an exciton photon quasiparticle,TMDs exciton polarons have the advantages of photons and excitons,such as the speed of light,spin selective valley excitation,and circular polarization related light emission.This thesis is mainly based on the theory of photonic crystal BIC and exciton polaron of TMDs,regulating photonic crystal BIC to achieve strong coupling and valley dependent polarization vortex emission.The research contents are as follows:1.The photonic crystal plates with different structural parameters and material parameters are studied.Theoretical analysis and simulation are carried out on the photonic crystal plate,and the frequency band structure of photonic crystal BIC is studied,as well as the quality factor of corresponding frequency band and the electric field distribution in different modes,realizing the optical BIC regulation in visible,mid-infrared and terahertz bands.2.A hybrid dimensional TMDs hypersurface composed of nanostructured 2H stacked TMDs crystals and single layer TMDs is proposed to achieve strong coupling of BIC and TMDs exciton polarons.Through data fitting and calculation,it is confirmed that the mixed dimensional hypersurface is in a strong coupling state.At the same time,a 3R stacked TMDs hypersurface was designed to support quasi BIC resonance and achieve strong coupling with exciton self hybridization.By adjusting the structural parameters of the q-BIC hypersurface,the anti cross behavior and Rabi splitting of exciton particles were observed.3.Bound states in the continuum and polarized vortices in the momentum space of a mixed dimensional TMDs hypersurface composed of nanostructured 2H stacked TMDs crystals and single layer TMDs were studied.The polarization state of the BIC far field,the phase distribution near point Γ,and the topological charge were calculated.A simulation was conducted,and a 50×50 structural unit was set up to obtain the intensity distribution and phase distribution of the far field through the excitation of circularly polarized Gaussian light.The field distribution in the cross section presents a hollow distribution,and the phase distribution presents a phase singularity,realizing the emission of valley dependent polarization vortices.