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Thermal radiation

About: Thermal radiation is a research topic. Over the lifetime, 12290 publications have been published within this topic receiving 197186 citations. The topic is also known as: heat radiation.


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Journal ArticleDOI
07 Mar 2002-Nature
TL;DR: It is demonstrated that by introducing a periodic microstructure into such a polar material (SiC) a thermal infrared source can be fabricated that is coherent over large distances (many wavelengths) and radiates in well defined directions.
Abstract: A thermal light-emitting source, such as a black body or the incandescent filament of a light bulb, is often presented as a typical example of an incoherent source and is in marked contrast to a laser. Whereas a laser is highly monochromatic and very directional, a thermal source has a broad spectrum and is usually quasi-isotropic. However, as is the case with many systems, different behaviour can be expected on a microscopic scale. It has been shown recently that the field emitted by a thermal source made of a polar material is enhanced by more than four orders of magnitude and is partially coherent at a distance of the order of 10 to 100nm. Here we demonstrate that by introducing a periodic microstructure into such a polar material (SiC) a thermal infrared source can be fabricated that is coherent over large distances (many wavelengths) and radiates in well defined directions. Narrow angular emission lobes similar to antenna lobes are observed and the emission spectra of the source depends on the observation angle--the so-called Wolf effect. The origin of the coherent emission lies in the diffraction of surface-phonon polaritons by the grating.

1,226 citations

01 Jan 2011
TL;DR: In this paper, the non-similar solutions are presented which depend on the Magnetic parameter M respectively, the obtained equations have been solved by explicit finite difference method and temperature and concentration profiles are discussed for the different values of the above parameters with different time steps.
Abstract: Unsteady heat and mass flow of a nanofluid past a stretching sheet with thermal radiation in the presence of magnetic field is studied. To obtain non-similar equation, continuity, momentum, energy and concentration equations have been non-dimensionalised by usual transformation. The non-similar solutions are presented here which depends on the Magnetic parameter M respectively . The obtained equations have been solved by explicit finite difference method. The temperature and concentration profiles are discussed for the different values of the above parameters with different time steps.

956 citations

Journal ArticleDOI
TL;DR: The experimentally measured root mean square fluctuation of the output meter of a microwave radiometer compares favorably with a theoretical value of 0.4°C, which corresponds to a minimum detectable power of 10-16 watt.
Abstract: The connection between Johnson noise and blackbody radiation is discussed, using a simple thermodynamic model. A microwave radiometer is described together with its theory of operation. The experimentally measured root mean square fluctuation of the output meter of a microwave radiometer (0.4°C) compares favorably with a theoretical value of 0.46°C. With an r-f band width of 16 mc/sec., the 0.4°C corresponds to a minimum detectable power of 10-16 watt. The method of calibrating using a variable temperature resistive load is described.

941 citations

Journal ArticleDOI
TL;DR: In this article, the difference between thermal and non-thermal radiation is accounted for by introducing the chemical potential of photons, which allows the calculation of absorption coefficients, of emission spectra of luminescent materials, and of radiative recombination lifetimes of electrons and holes in semiconductors.
Abstract: In a thermodynamic treatment electromagnetic radiation of any kind is described. The difference between thermal and non-thermal radiation is accounted for by introducing the chemical potential of photons. Instead of an effective temperature all kinds of radiation have the real temperature of the emitting material. As a result Planck's law for thermal radiation is extended to radiation of any kind. The concept of the chemical potential of radiation is discussed in detail in conjunction with light-emitting diodes, two-level systems, and lasers. It allows the calculation of absorption coefficients, of emission spectra of luminescent materials, and of radiative recombination lifetimes of electrons and holes in semiconductors. Theoretical emission spectra are compared with experimental data on GaAs light-emitting diodes and excellent agreement is obtained.

895 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023375
2022749
2021575
2020636
2019663
2018618