Research On Three-level Quantum Coupling System In Terahertz Band

Optical coupling in three-level system is a very practical and developing research field.Two optical bump beams with different amplitude cause coherence cancellation and enable the effect of electromagnetically induced transparency and stimulated raman adiabatic passage on optical coupling regulation,which has great application potential in the field of optical communication.But because of the limitation of quantum system research conditions,the energy coupling mechanism research is difficult,this hindered the further development of the theory.In recent years,with the development of metamaterials and quantum-optical analogy research,how to use the classic system to study the three-level quantum coupling system become an urgent problem to be solved.In this thesis,we designed two kinds of classical systems to study the energy coupling in terahertz band.The details are as follows:(1)metamaterial structure based on the effect of Electromagneticaly induced Transparency.We use metamaterials simulates the quantum EIT effect of three level system in the terahertz band.By disiging the structure consist of bright mode and dark mode and using photosensitive silicon semiconductor,we get the EIT effect at center resonance frequency 0.69 THz and reached more than 90% of the modulation depth,we then monitored the electromagnetic field on the surface of the unit cell and researched the mechanism of the coupling process.The simulation results show that the pump light used to actively regulate the EIT-like effect,lead to the completely coherent cancellation of the energy,so the EITlike effect with very high modulation depth is excited.(2)Surface plasmon-polaritons waveguide structures based on stimulated Raman adibatic passage technology.The SPPS waveguide with terahertz band is designed by applying the stimulated Raman adiabatic channel technology.By designing the coupling structure of curved waveguide and straight waveguide with different spacing and using ITO electronic control material to switch the metal insulation of the straight waveguide,98% of the SPPS energy transfer efficiency from the input waveguide to the output waveguide.The simulation results show that the three-waveguide structure designed based on STIRAP technology can not only achieve high transmission efficiency,but also actively switch the output target waveguide,and has good robustness and broadband characteristics.