Thermal Radiation Energy Density Research Articles

Thermal coherence properties of topological insulator slabs in time-reversal symmetry breaking fields

We first develop a general Green's-function method for the slab geometry, which can handle quite complex conversions between the different polarized radiation modes. Then by using the method, we study the near field thermal coherence properties of a slab of ${Z}_{2}$ topological insulator (TI) with a finite thickness. Under a strong enough external magnetic field, the gapless helical Dirac fermions on the TI surfaces can acquire an energy gap larger than the photon energy of the radiation field at the Dirac point. This gapped surface states can couple strongly with the waveguide modes in the bulk of the TI slab, which thus induces an electromagnetic resonance. Exactly due to the resonance, the coherence properties of the thermal radiation field can be modified dramatically. For ${Z}_{2}$ topological insulators, the parameter regime with the surface Hall conductivity half integer quantized is unique. We demonstrated that within the parameter regime, for a TI slab of a proper thickness, the thermal radiation energy density can be enhanced very much, and the coherence length of the thermal radiation field can be as long as twice that of SiC.

Effective temperature of thermal radiation from non-uniform temperature distributions and nanoparticles

We study thermal radiation properties from non-uniform temperature distributions and nanoparticles, and define effective temperature. Conventionally, the temperature of a body is measured by fitting with the blackbody radiation spectrum, which assumes a uniform temperature throughout the body. We show the energy density of thermal radiation for non-uniform temperature distribution of the body and derive the effective temperature. Furthermore, the energy density of thermal radiation from nanoparticles is derived and the effective temperature of the body is shown to depend on the particle size.

Relationship between power density distribution and homogenization of diamond film in the multifilament CVD system

Periodical macro-stripes have been found on diamond film prepared on a Si substrate by the multifilament chemical vapor deposition (CVD) method when the filament-substrate distance is less than 2 mm. The properties of the stripe on the film were characterized qualitatively by a scanning electron microscope (SEM) and Raman scattering spectrometer. The measurement results show that this stripe corresponds to the different kinds of the microstructure and thickness of the film. Through calculation of the thermal radiation energy density distribution on the surface of substrate, this phenomenon can be explained successfully.