| This thesis is concerned with how the transport and emission of thermal electromagnetic fields can be engineered using nanophotonic structures.;Since vacuum is commonly thought to be the best thermal insulator, the ability for the multi-layer photonic crystals to suppress thermal conductance below that of vacuum is especially significant. We find that there exists a lower limit for such conductance suppression with respect to vacuum, and this limit is generally independent of the thicknesses of the layers. Furthermore, such structural independence reveals the fact that distribution of photonic bands in frequency space is ergodic.;Lastly, we examine the properties of thermal electromagnetic fields emitted from lossy dielectric slabs. At near-field distance from the slab surface, the coherence length of the emitted fields in free space can be drastically different from that of the blackbody, due to the excitation of waveguide modes, and the fluctuating surface charges.;First, a multi-layer photonic crystal is considered as the thermal-conducting medium. The crystal is composed of alternate layers of lossless dielectric slabs and vacuum, such that heat transport is coherent and is only due to photons. The thermal-conducting behavior of the crystal is determined by two opposing mechanisms: the enhancing effect from evanescent tunneling of photons, and the suppressing effect due to the photonic band gaps. By tuning the thicknesses of the layers, we can control the relative dominance of these two effects, and the medium can be tuned from being thermally more conducting, to thermally more insulating than vacuum at a fixed temperature. |
