Coherent Thermal Emission From Modified Periodic Multilayer Structures

2006 ◽  
Vol 129 (1) ◽  
pp. 17-26 ◽  
Author(s):  
B. J. Lee ◽  
Z. M. Zhang
Keyword(s):  
Surface Waves ◽  
Multilayer Structure ◽  
Thermal Emission ◽  
Cavity Resonance ◽  
Support Surface ◽  
Emission Sources ◽  
Surface Polaritons ◽  
Propagating Waves ◽  
Coherent Emission ◽  
And Control

Enhancement of thermal emission and control of its direction are important for applications in optoelectronics and energy conversion. A number of structures have been proposed as coherent emission sources, which exhibit a large emissivity peak within a narrow wavelength band and at a well-defined direction. A commonly used structure is the grating, in which the excited surface polaritons or surface waves are coupled with propagating waves in air, resulting in coherent emission for p polarization only. One-dimensional photonic crystals can also support surface waves and may be modified to construct coherent emission sources. The present study investigates coherent emission from a multilayer structure consisting of a SiC film coated atop a dielectric photonic crystal (PC). By exciting surface waves at the interface between SiC and the PC, coherent emission is predicted for both p and s polarizations. In addition to the excitation of surface waves, the emission from the proposed multilayer structure can be greatly enhanced by the cavity resonance mode and the Brewster mode.

Coherent Thermal Emission From Modified Periodic Multilayer Structures

2005 ◽  
Author(s):  
B. J. Lee ◽  
Z. M. Zhang
Keyword(s):  
Photonic Crystal ◽  
Surface Waves ◽  
Thermal Emission ◽  
Cavity Resonance ◽  
Support Surface ◽  
Emission Sources ◽  
Surface Polaritons ◽  
Propagating Waves ◽  
Coherent Emission ◽  
And Control

Enhancement of thermal emission and control of its direction are important for applications in optoelectronics and energy conversion. A number of structures have been proposed as coherent emission sources, which exhibit a large emissivity peak within a narrow wavelength band and at well-defined directions. A commonly used structure is gratings, in which the excited surface polaritons or surface waves are coupled with propagating waves in air to produce coherent emission for p polarization. One-dimensional photonic crystals can also support surface waves but have not been applied as coherent emission sources. The present study demonstrates that coherent emission can be achieved by the use of a multilayer structure consisting of periodic layers (i.e., photonic crystal) coated with a polar material such as SiC. By excitation of surface waves at the interface between SiC and the photonic crystal, coherent emission is predicted for both p and s polarization. In addition to the excitation of surface waves, the emission from the proposed structure can be largely enhanced by the cavity resonance mode, which is very similar to that of Fabry-Perot etalon, as well as by the Brewster mode that occurs only for p polarization.

Enhanced Coherency of Thermal Emission From SiC by Coupled Resonant Cavity Structure

2008 ◽  
Author(s):  
Nir Dahan ◽  
Avi Niv ◽  
Yuri Gorodetski ◽  
Vladimir Kleiner ◽  
Erez Hasman
Keyword(s):  
Surface Waves ◽  
Thermal Emission ◽  
Near Field ◽  
Resonant Cavity ◽  
Spatial Coherence ◽  
Support Surface ◽  
Amorphous Sio2 ◽  
Coherent Coupling ◽  
Cavity Structure ◽  
Order Of Magnitude

Surface waves have been shown to play a key role in spontaneous thermal emission in the near-field as well as the coherence and the polarization properties of the nonradiative field. The near-field coherence of the delocalized nonradiative surface waves can be transferred into radiative fields by introducing a shallow grating on the surface. We show that the coherency of the thermal radiation can be enhanced by an order of magnitude compared with the coherency imposed by the delocalized surface waves. The enhanced coherency is due to coherent coupling between resonant cavities obtained by surface standing waves, where each cavity supports localized field that is attributed to coupled surface waves. We realized coupled resonant cavity structure on amorphous SiO2 and crystalline SiC, both support surface phonon-polaritons, to demonstrate extraordinary coherent thermal emission with a high quality factor of 600 and a spatial coherence length of 760λ.

scholarly journals High spatial resolution imaging of methane and other trace gases with the airborne Hyperspectral Thermal Emission Spectrometer (HyTES)

2016 ◽  
Author(s):  
G. C. Hulley ◽  
R. M. Duren ◽  
F. M. Hopkins ◽  
S. J. Hook ◽  
N. Vance ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Thermal Emission ◽  
High Spatial Resolution ◽  
Matched Filter ◽  
Study Data ◽  
High Spectral Resolution ◽  
Emission Sources ◽  
Source Attribution ◽  
Economic Sectors ◽  
Strong Emission

Abstract. Currently large uncertainties exist associated with the attribution and quantification of fugitive emissions of criteria pollutants and greenhouse gases such as methane across large regions and key economic sectors. In this study, data from the airborne Hyperspectral Thermal Emission Spectrometer (HyTES) have been used to develop robust and reliable techniques for the detection and wide-area mapping of emission plumes of methane and other atmospheric trace gas species over challenging and diverse environmental conditions with high spatial resolution that permits direct attribution to sources. HyTES is a pushbroom imaging spectrometer with high spectral resolution (256 bands from 7.5–12 µm), wide swath (1–2 km), and high spatial resolution (~2 m at 1 km altitude) that incorporates new thermal infrared (TIR) remote sensing technologies. In this study we introduce a hybrid Clutter Matched Filter (CMF) and plume dilation algorithm applied to HyTES observations to efficiently detect and characterize the spatial structures of individual plumes of CH4, H2S, NH3, NO2, and SO2 emitters. The sensitivity and field of regard of HyTES allows rapid and frequent airborne surveys of large areas including facilities not readily accessible from the surface. The HyTES CMF algorithm produces plume intensity images of methane and other gases from strong emission sources. The combination of high spatial resolution and multi-species imaging capability provides source attribution in complex environments. The CMF-based detection of strong emission sources over large areas is a fast and powerful tool needed to focus more computationally intensive retrieval algorithms to quantify emissions with error estimates, and is useful for expediting mitigation efforts and addressing critical science questions.

Production and Control of Low-Pressure Ar and CF4Plasmas Using Surface Waves

1998 ◽  
Vol 37 (Part 1, No. 4B) ◽  
pp. 2406-2409 ◽  
Author(s):  
Masaaki Nagatsu ◽  
Ivan Ghanashev ◽  
Shin Morita ◽  
Hideo Sugai
Keyword(s):  
Surface Waves ◽  
Low Pressure ◽  
And Control

Gastroduodenal mucus bicarbonate barrier: protection against acid and pepsin

2005 ◽  
Vol 288 (1) ◽  
pp. C1-C19 ◽  
Author(s):  
Adrian Allen ◽  
Gunnar Flemström
Keyword(s):  
Ph Gradient ◽  
Support Surface ◽  
First Line ◽  
Physiological Conditions ◽  
Neutral Ph ◽  
Primary Function ◽  
Gel Layer ◽  
Mucus Gel ◽  
And Control

Secretion of bicarbonate into the adherent layer of mucus gel creates a pH gradient with a near-neutral pH at the epithelial surfaces in stomach and duodenum, providing the first line of mucosal protection against luminal acid. The continuous adherent mucus layer is also a barrier to luminal pepsin, thereby protecting the underlying mucosa from proteolytic digestion. In this article we review the present state of the gastroduodenal mucus bicarbonate barrier two decades after the first supporting experimental evidence appeared. The primary function of the adherent mucus gel layer is a structural one to create a stable, unstirred layer to support surface neutralization of acid and act as a protective physical barrier against luminal pepsin. Therefore, the emphasis on mucus in this review is on the form and role of the adherent mucus gel layer. The primary function of the mucosal bicarbonate secretion is to neutralize acid diffusing into the mucus gel layer and to be quantitatively sufficient to maintain a near-neutral pH at the mucus-mucosal surface interface. The emphasis on mucosal bicarbonate in this review is on the mechanisms and control of its secretion and the establishment of a surface pH gradient. Evidence suggests that under normal physiological conditions, the mucus bicarbonate barrier is sufficient for protection of the gastric mucosa against acid and pepsin and is even more so for the duodenum.

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