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Absorption (electromagnetic radiation)

About: Absorption (electromagnetic radiation) is a research topic. Over the lifetime, 76674 publications have been published within this topic receiving 1381221 citations.


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Journal ArticleDOI
TL;DR: In this paper, coupled fused-silica microspheres were used to investigate the effect of interference between coresonant whisperinggallery modes of the two spheres and the observed effects can enhance microresonator performance in various applications.
Abstract: Optical behavior analogous to electromagnetically induced transparency and absorption is observed in experiments using coupled fused-silica microspheres. This behavior results from interference between coresonant whispering-gallery modes of the two spheres. Coupled-resonator-induced transparency and absorption are observed. Which effect is seen depends on the strength of coupling of incident light from a tapered fiber into the first sphere and on the strength of coupling between the two spheres. The observed effects can enhance microresonator performance in various applications.

215 citations

Journal ArticleDOI
TL;DR: In this article, the electronic and optical properties of undoped mixed-phase TiO2 nanoparticles were investigated using UV and inverse photoemission, low intensity X-ray photoelectron (XP), and diffused reflectance spectroscopy methods.
Abstract: TiO2 is one of the most promising candidate materials for clean-energy generation and environmental remediation. However, the larger-than 3.1 eV bandgap of perfectly crystalline TiO2 confines its application to the ultraviolet (UV) range. In this study, the electronic and the optical properties of undoped mixed-phase TiO2 nanoparticles were investigated using UV and inverse photoemission, low intensity X-ray photoelectron (XP), and diffused reflectance spectroscopy methods. The facile solution-phase synthesized nanoparticles exhibited a midgap-states-induced energy gap of only ∼2.2 eV. The diffused reflectance spectrum showed sub-bandgap absorption due to the existence of a large Urbach tail at 2.2 eV. The UV photoemission spectrum evidenced the presence of midgap states. The 2.2 eV energy gap enables the nanoparticles to be photoactive in the visible energy range. The gas-phase CO2 photoreduction test with water vapor under visible light illumination was studied in the presence of the synthesized TiO2 na...

215 citations

Journal ArticleDOI
David Redfield1
TL;DR: In this article, a semiquantitative calculation is made of such broadening due to impurities in semiconductors having direct absorption edges, and reasonable agreement is found with published absorption tails of InAs, for both the magnitude of the effect and its dependence on impurity concentration.
Abstract: The electric fields of charged defects in a solid broaden its fundamental optical absorption edge by a mechanism which is an internal analog of the Franz-Keldysh effect. Using this analogy, a semiquantitative calculation is made of such broadening due to impurities in semiconductors having direct absorption edges. Without the use of any adjustable parameters, reasonable agreement is found with published absorption tails of InAs, for both the magnitude of the effect and its dependence on impurity concentration. It is proposed that such effects account for the common Urbach's rule observations, and a qualitative discussion is given for the corresponding effects in insulators.

214 citations

Journal ArticleDOI
TL;DR: In this paper, two approaches have been adopted in attempting to determine the strength of the one-phonon infrared absorption by the B nitrogen aggregate in diamond, which is complicated because diamonds in which the B aggregate is the only point defect also contain extended defects that may or may not involve nitrogen.
Abstract: Two approaches have been adopted in attempting to determine the strength of the one-phonon infrared absorption by the B nitrogen aggregate in diamond. On the one hand, we have heat treated purely type IaA specimens with known infrared absorption strengths (and thus also known nitrogen concentrations) to bring about partial aggregation of the A centres to B centres, monitoring changes in the strengths of the A, and resultant B, one-phonon components by decomposition of the ensuing infrared spectra. Secondly, we have made direct chemical assays of nitrogen in diamonds that show dominant B absorption features. This approach is complicated because diamonds in which the B aggregate is the only point defect also contain extended defects that may or may not involve nitrogen. These defects may or may not, in turn, contribute to absorption in the one-phonon region. Nevertheless, the nitrogen concentrations have been measured for two distinct groups of diamonds that both uncritically might at first glance ...

214 citations

Journal ArticleDOI
G. Frank1, E. Kauer1, H. Köstlin1
TL;DR: In this paper, the free electron densities of up to 1021 cm−3 and mobilities in the range 10−70 cm2 V−1s−1 can be obtained by means of an appropriate doping and/or oxygen deficit.

214 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2022185
20213,106
20202,866
20192,953
20182,876
20172,679