Investigation Of Active Metamaterial And Nonlinear Metamaterial Based On FDTD Method

A metamaterial is an artificial material fabricated and engineered to achieve some novel properties that are not exist in nature materials.Since the concept of metamaterials was first mentioned by Soviet scientist Veselago in 1968,the field of metamaterials has demonstrated spectacular theoretical and experimental progresses in recent years.Electromagnetic metamaterials have numerous novel applications,which make them become a hot research topic.In recent years,the nanotechnologies and laser techniques associated with nanoscale metamaterials are becoming increasingly sophisticated,which allows for investigating nanoscale unit cell metamaterials interacting with very high-power laser.The interaction between photons and electrons in metamaterials can stimulate surface plasmon polaritons(SPPs),will enhance the electromagnetic field and present many fancy optical applications.Investigation of metamaterials by using computational electromagnetic theories is an important step for developing and understanding metamaterials.A FDTD algorithm is frequently used to study the multiphysics problems of different applications based on metamaterials.This thesis investigates the applications of metamaterials by numerical methods.The main points are as follows:1.A self-consistent approach is proposed to study a coupled system of gain medium and metamaterials.Using a four-level atomic system,an artificial source is introduced to simulate the spontaneous emission process in the QDs.We numerically show that the metamaterials can lead to multifold enhancement and spectral narrowing of photoluminescence from QDs.These results are consistent with recent experimental studies.2.A time-domain solution of the hydrodynamic model that describes a free electron gas in metals is presented.Extending beyond the local-linear response,the hydrodynamic model enables numerical investigation of nonlocal and nonlinear interactions between electromagnetic waves and metallic metamaterials.Using the finite-difference time-domain method,the proposed model is treated in a self-consistent manner and well captures charge,energy and angular momentum conservation laws governing the high-order harmonic generations.The model yields nonlinear optical responses for complex metallic metamaterials irradiated by a variety of waveforrms.3.There applications of nonlinear metamaterials are presented.(1)We numerically verified our model by calculating the nonlinear response for metasurfaces with different rotational symmetries.The results were compared to the selection rules of SHG.(2)Using electro-optic effect of metasurface to generate broadband terahertz signal.(3)We demonstrate on-chip plasmonic sum frequency generation(SFG)with a metal-dielectric-metal metamaterials.All of the numerical results are consistent with theoretical results or experimental studies.