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Exact Evaluation of K. Jensen's General Thermal-Field-Photoemission Integral
摘要： Jensen has developed a general expression for the current density JGT F emitted from a surface by thermal or field emission, or by a combination of these processes; he has also shown how the same expression may be analytically extended to compute the current density due to photoemission. JGT F is expressed as a single integral, which Jensen evaluates analytically in certain limits and numerically outside those limits. In this paper, we show how the integral may be expressed generally as convergent series that are easily evaluated numerically for all values of the physical parameters. No real or apparent singularities, like those that appear in the function Z defined by Jensen occur in the series obtained here.
关键词： photoemission,field emission,thermal emission,Electron emission
更新于2025-09-23 15:22:29
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Apparent Spectral Shift of Thermally Generated Surface Phonon-Polariton Resonance Mediated by a Nonresonant Film
摘要： The physical origin of the spectral shift of a thermally generated surface phonon-polariton (SPhP) resonance of a silicon carbide (SiC) bulk mediated by a nonresonant film is explained. The local density of electromagnetic states (LDOS) in a nonresonant intrinsic silicon (Si) film due to thermal emission by SiC, derived using fluctuational electrodynamics, exhibits a local maximum near the SPhP-resonant frequency in addition to a lower frequency resonance generated by gap modes emerging in the vacuum gap separating the SiC and Si layers. Multiple reflections within the vacuum gap also induce a LDOS drop around the SPhP-resonant frequency. As a result, depending on the film thickness to vacuum gap ratio and the location where the LDOS is calculated in the film, the low-frequency resonance can dominate the LDOS, such that the SPhP resonance appears to be redshifted. A similar spectral behavior is observed on the monochromatic radiative heat flux absorbed by the Si film. It is shown that apparent spectral (red and blue) shifts of the SPhP resonance mediated by a nonresonant film are bounded by the transverse and longitudinal optical phonon frequencies of SiC. This work is of importance in applications involving dissimilar materials, such as thermophotovoltaics and thermal rectification, where gap modes may significantly disrupt flux resonance. Gap modes may also be at the origin of the resonance redshift systematically observed in near-field thermal spectroscopy.
关键词： local density of electromagnetic states,thermal emission,surface phonon-polariton,spectral shift,near-field thermal spectroscopy
更新于2025-09-23 15:21:01
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Handbook of Exoplanets || Characterization of Exoplanets: Secondary Eclipses
摘要： When an exoplanet passes behind its host star, we can measure the time of the occultation, its depth, and its color. In this chapter we describe how these observables can be used to deduce physical characteristics of the planet such as its averaged dayside emission, departures from uniform disk illumination, or a precise measurement of the orbital eccentricity. This technique became a reality in 2005; in this chapter we describe the basics of the technique, its main results in the last 12 years, and the prospects for the years to come. This chapter includes a table with references to all published detections of secondary eclipses until December 2017.
关键词： reflected light,exoplanets,orbital eccentricity,thermal emission,secondary eclipses
更新于2025-09-23 15:21:01
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Laser-induced thermal emission of rough carbon surfaces
摘要： The decay of thermal emission of rough surface layers of different carbon materials under the pulsed laser excitation is analyzed both theoretically and experimentally. For pulsed laser heating of rough surfaces, computer simulations revealed that laser-induced thermal radiation is mainly emitted by peaks of the surface relief, and the emission decay time depends on the relation between the laser penetration depth and the temperature diffusion length. It is also concluded that the presence of surface roughness can significantly increase the emission decay time. In the experiments, carbon materials with different thermal characteristics were used; however, all of the investigated samples demonstrated close values of the emission decay time. This fact shows that the material’s characteristics on the peaks of surface relief are similar for different carbon materials at high temperature.
关键词： laser-induced thermal emission,rough surfaces,carbon materials
更新于2025-09-16 10:30:52
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Selective thermal radiation at longitudinal optical phonon energy under geometric condition of metal-semiconductor mesa stripe structures
摘要： Selective thermal emission at approximately 284 cm?1 with a line width of 13 cm–1 at 628 K is obtained by heating the Au-GaAs mesa-type line and space structures. This emission demonstrates a characteristic polar radiation distribution of electric dipoles and a wavelength independent of the structure size or the direction of emission; thus, it is ascribed to thermally generated electric dipoles resonating with the longitudinal optical phonon energy. This dipole is formed by the interface polarization charges of metal-GaAs-metal stripes. These distinct features are different from the radiation properties of interface phonon polaritons or electronic systems such as intersubband transitions of quantum wells. It is estimated that the mesa height and GaAs space width ranging from hundreds of nanometers to several micrometers provide high generation ef?ciency of electric dipoles and resultant radiation at high temperatures.
关键词： metal-semiconductor mesa stripe structures,longitudinal optical phonon,electric dipoles,thermal emission
更新于2025-09-10 09:29:36
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Dependences of the Thermophysical Parameters of Activated Thermal-Emission Cathodes on the Current in a Stable Arc Discharge
摘要： The influence of electrical current (in the range 20–150 A) on the thermophysical characteristics of activated thermal cathodes (W + 2% ThO2) in a freely glowing low-pressure argon arc is investigated. For the first time, the dependences of key cathode parameters, such as the heat flux at the electrode, the voltage equivalent of the heat, the specific erosion, and the distributions of the temperature and work function over the extension length of the cathode from the holder, are obtained. A nonmonotonic dependence of the specific erosion on the electrical current with a minimal level at 50–60 A is noted.
关键词： thermophysical parameters,work function,thermal-emission cathodes,arc discharge,specific erosion
更新于2025-09-04 15:30:14
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Near-Field and Far-Field Thermal Emission of an Individual Patch Nanoantenna
摘要： The far-field spectral and near-field spatial responses of an individual metal-insulator-metal nanoantenna are reported, using thermal fluctuations as an internal source of the electromagnetic field. The far-field spectra, obtained by combining Fourier transform infrared spectroscopy with spatial modulation based on a light falloff effect in a confocal geometry, have revealed two distinct emission peaks attributed to the excitation of the fundamental mode of the nanoantenna at two distinct wavelengths. Superresolved near-field images of the thermally excited mode have been obtained by thermal radiation scanning tunneling microscopy. Experimental results are supported by numerical simulations showing that it is possible to excite the same mode at different wavelengths near a resonance of the insulating dielectric material forming the antenna.
关键词： near-field,nanoantenna,thermal emission,microscopy,spectroscopy,far-field
更新于2025-09-04 15:30:14
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Heat Resisting Metallic Meta-Skin for Simultaneous Microwave Broadband Scattering and Infrared Invisibility Based on Catenary Optical Field
摘要： Metallic skins are widely used in practical engineering owing to their inherent advantages in mechanical and physical characteristics. In this paper, a metasurface skin composed of subwavelength metallic gratings with space-variant orientations has been proposed to realize exotic electromagnetic properties in microwave and infrared regimes. Equivalent circuit theory and transfer matrix method have been adopted to quantitatively describe the optical fields and dispersion with high accuracy in a catenary form. Based on these analyses, broadband and wide-angle radar cross-section (RCS) reduction for microwave has been simulated and experimentally demonstrated. Additional characteristics such as high temperature resistance and low infrared thermal emission are also verified. It is believed that these results may provide a new platform to achieve multifunctional electromagnetic devices and are promising for many applications.
关键词： scattering,catenary optics,metasurface,thermal emission,all-metal metasurfaces
更新于2025-09-04 15:30:14