Study On The Near-field Thermal Radiation Of Periodically Stratified Structure

With the development of nanoscience and technology, increasingly interests havebeen dropped in thermal radiation at nano/microscale. In the nano/microscale, themacroscopic heat transfer theory has been unable to meet the micro scale problem in thenear field. As the near field thermal transmission theory now is not mature enough, thestudy of near field thermal transfer can reference to macroscopic heat transfer theory, suchas radiation theory, Newton’s law of cooling and the electromagnetic theory. Study on heattransfer in the near field is essential to further explore the essence of heat. Regarding theelectron, phonon even photon as the heat carrier in micro/nano scale heat transfer problemsin the near field has certain theoretical basis. The periodically stratified structure is typical1-D photonic crystal structure. To study the mechanism of thermal radiation in thenear-field can improve the knowledge of heat transfer at macroscale. Based on thefluctuation-dissipation theorem, this dissertation presents detailed analysis of near-fieldthermal radiation for periodically stratified structure.Firstly, the radiative heat transfer between two parallel plates separated by a vacuumgap is analyzed based on the fluctuational electrodynamics. We combine with the transfermatrix theory of multilayer structure and analyze the reflectivity and transmissivity ofmultilayer structure. The transmittance of periodically stratified structure is obtained. Thetransfer matrix method is presented for further analyzing the characters of periodicallystratified structure.Secondly, calculate the density of states (DOS) near the semi-infinite medium surfacein the near-field by the use of the dyadic Green’s function method. We combine with thedensity calculation method in the near field and calculate the density of states of differentforms of semi-infinite medium in the near field. Then we analyze the component of DOSand the near-field evanescent wave determining on the density of states under the conditionof near field. The effect of near field distance and the material is showed at last. Finally, the analysis of near-field thermal radiation of periodically stratified structureis presented. We research the transmission mechanism theory of near field thermalradiation between two semi-infinite parallel plates and that between two finite thicknessfilms. With the corresponding conditions in the near field simplified, approximatecalculation is applied in calculating the near-field thermal radiation heat transfercoefficient between two semi-infinite media. We get the formula related to the distancesquare inverse ratio. Then we make an approximate calculate for the heat transfer of nearfield between two thin films of finite thickness and derive the radiative heat transfercoefficient related with film thick and distance. Analyzing the two kinds of extremeconditions of the near field thermal transmission properties between two finite thicknessfilms is displayed.