Infrared Thermal Radiation And Near Field Radiative Heat Transfer Of Metamaterials

Due to the unique electromagnetic characteristics and the spectrum tuning ability, metamaterials have great opportunities for a tremendous amount of applications and act as a workhorse in many research fields, such as the rational use of solar energy and effective recovery of industrial waste heat. Classical theory of thermal radiation may lose its validity when the radiation distance is comparable with or smaller than the thermal wavelength. By properly designing the structure of metamaterial, it should assist in tuning the spectrum of near field radiative heat transfer between metamaterials, understanding the physical mechanism of heat transfer and realizing functional metamaterial devices.In this thesis, the thermal radiation and near field heat transfer based on several kinds of typical metamaterial are investigated. The physical mechanisms on the enhancement of thermal radiation and near field heat transfer are discussed, which provide theoretical basis on the spectum tuning and frequency selective enhance d thermal radiation and near field heat transfer. The detail contents can be divided into the following parts.Based on fluctuation electrodynamics, in combination with fluctuation dissipation theorem and Green function method, the analytical expression of the local density of state is given where the magnetic response within metamaterial is considered. Since negative permittivity and permeability of isotropic dielectric cubic arrays metamaterial can be achieved and both s polarized and p polarized surface waves are supported, we have investigated the near field thermal radiation of all dielectric metamaterial and the influence of separation distance to the local density of state and heat flux. Results show that the electric dipole resonance and magnetic dipole resonance within all dielectric metamaterial contribute to the enhanced near field radiation. The energy transmission fator and spatial coherence of all dielectric metamaterial are also analyzed, which should assist in realizing the enhancement of near field thermal radiation by nonpolar dielectric media.The metal-dielectric-metal sandwich-like fishnet metamaterial(FMM) can achieve negative permittivity and permeability in the near infrared, which should benefit the thermophotovoltaic conversion working at high temperature. Therefore, the FMM working in the near infrared is designed, and the near field thermal radiation and heat transfer between FMM are further investigated. Results show that multiple magnetic resonances within FMM contribute to the enhanced near field radiation and heat transfer, and additional frequency channels are opened compared with that of conventional media or other metamaterials. By considering the anisotropic characteristics, combining with the SPP dispersion within FMM, the near field radiative heat tranfer and the spatial coherence of FMM are further analyzed.Hyperbolic wavevector distribution is supported by hyperbolic metamaterial(HMM) which is composed of metal(metal-like)-dielectric multi-layered structure, and the local density of state should be clearly modulated by the radiation modes with large wavevectors. Therefore, the surface phonon polariton and Bloch mode mediated near field radiative heat transfer between HMM based on Si C-Si O2 multilayer structure is investigated. By considering the influence of layer thic kness and separation distance to the heat transfer coefficient, we have obtained the optimized heat transfer coefficient and the maxmium absorption meanpower of Si C nanosphere. Results show that the heat transfer coefficient of HMM at surface phonon polariton resonant frequency of Si C can be thirty percent larger than that of bulk Si C. In addition, the influence of loss factor of the metal-like layer to the near field radiative heat transfer is discussed by taking the doped Si-Ge HMM as an example. This work is meaningful to improve the imaging quality of near-field thermal scanning system.The design of infrared metamaterial perfect absorption should assist in realizing frequency selective absorber and thermal radiator devices, and the absorption characteristics of the L-shaped metamaterial in the infrared are investigated. The influence of incident angle, azimuth angle, polarized direction and L-shaped geometry to the absorption characteristics are analyzed. Results reveal the the dual-band absorption mechanism of magnetic dipole resonance. In addition, the LC circuit model is used to predict the resonant frequencies of absorption. The L-shaped metamaterial is also fabricated by electron beam etching method, and the absorption spectrum of the L-shaped metamaterial is measured in experiment.