scholarly journals Causes of Color in Minerals and Gemstones

2001 ◽  
Vol 9 (2) ◽  
pp. 14-17
Author(s):  
Paul F. Hlava
Keyword(s):  
Emission Spectrum ◽  
White Light ◽  
Emission Spectra ◽  
Light Sources ◽  
Physical Phenomena

The colors that one sees when looking at a mineral or gemstone are due to the response of that person's eye to the energies of the light, the emission spectrum of the illumination, and, most importantly, physical phenomena in the material that cause some colors to be absorbed while others are undisturbed or enhanced. It is beyond the scope of this article to do more than touch on the physiology of the eye that allows us to see colors. Likewise, we will not dwell on the emission spectra of various light sources. Rather, we will concentrate on the various ways in which materials, especially minerals and their heights of perfection, gemstones, produce color from white light.

scholarly journals Quantum Dot–Polyfluorene Composites for White-Light-Emitting Quantum Dot-Based LEDs

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2487
Author(s):  
Mariya Zvaigzne ◽  
Irina Domanina ◽  
Dmitriy Il’gach ◽  
Alexander Yakimansky ◽  
Igor Nabiev ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Emission Spectrum ◽  
Polymer Matrix ◽  
White Light ◽  
Light Emission ◽  
Structural Instability ◽  
Organic Ligands ◽  
Light Sources ◽  
Light Emitting ◽  
Chemical Structures

Colloidal quantum dots (QDs) are a promising luminescent material for the development of next generation hybrid light-emitting diodes (QDLEDs). In particular, QDs are of great interest in terms of the development of solid-state light sources with an emission spectrum that mimics daylight. In this study, we used CdSe(core)/ZnS/CdS/ZnS(shell) QDs with organic ligands mimicking polyfluorene and its modified derivatives to obtain QD–polymer composites emitting white light. We found that the emission of the composites obtained by spin-coating, being strongly dependent on the chemical structure of the polymer matrix and the QD-to-polymer mass ratio, can be accurately controlled and adjusted to bring its emission spectrum close to the spectrum of daylight (CIE coordinates: 1931 0.307; 0.376). Moreover, the light emission of these composites has been found to be temporally stable, which is due to the minimal structural instability and volume-uniform charge and energy transfer properties. Thus, the use of the synthesized polyfluorene-based organic ligands with controllable chemical structures adaptable to the structure of the polymer matrix can significantly increase the stability of white light emission from QD composites, which can be considered promising electroluminescent materials for fabrication of white QDLEDs.

Crystalline Silicon White Light Sources Driven by Optical Resonances

Nano Letters ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2397-2405
Author(s):  
Jin Xiang ◽  
Mincheng Panmai ◽  
Shuwen Bai ◽  
Yuhao Ren ◽  
Guang-Can Li ◽  
...  
Keyword(s):  
White Light ◽  
Crystalline Silicon ◽  
Light Sources ◽  
Optical Resonances

scholarly journals Photocatalytic Performance of ZnO: Al Films under Different Light Sources

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Prashant Pradhan ◽  
Juan Carlos Alonso ◽  
Monserrat Bizarro
Keyword(s):  
White Light ◽  
Irradiation Time ◽  
Zno Films ◽  
Light Sources ◽  
X Ray Diffraction ◽  
Treatment Processes ◽  
Vis Spectroscopy ◽  
Doped Zno ◽  
Very High ◽  
High Degradation Rate

ZnO and Al doped ZnO films were produced by spray pyrolysis. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectroscopy, and photoluminescence. Their photocatalytic activity was evaluated by the decomposition of the methyl orange dye using different light sources: ultraviolet light, artificial white light, and direct sunlight. The films were also tested under darkness for comparison. The ZnO films were able to degrade the test pollutant under UV and sunlight in more than a 60% after 180 min of irradiation and a scarce degradation was obtained using white light. However, the Al doped ZnO films presented a very high degradation rate not only under UV and sunlight (100% degradation), but also under white light (90% degradation after the same irradiation time). An unexpected high degradation was also obtained in the dark, which indicates that a nonphotonic process is taking place parallel to the photocatalytic process. This can be due to the extra electrons—provided by the aluminum atoms—that migrate to the surface and produce radicals favoring the decomposition process even in the dark. The high activity achieved by the ZnO: Al films under natural conditions can be potentially applied to water treatment processes.

scholarly journals System efficiency of laser-based white light

2014 ◽  
Vol 3 (5-6) ◽  
Author(s):  
Roland Lachmayer ◽  
Alexander Wolf ◽  
Gerolf Kloppenburg
Keyword(s):  
Thermal Management ◽  
White Light ◽  
High Power ◽  
Laser Diodes ◽  
Light Sources ◽  
System Efficiency ◽  
Light Emitting ◽  
Scale Down ◽  
Color Rendering ◽  
Product Weight

AbstractFor many lighting applications, light-emitting diodes (LEDs) are replacing traditional light sources providing the possibility for smart and efficient systems as well as a reduction in the product weight. A next step in this development is the integration of laser-based light sources to increase luminance and to further scale down the optics possibly leading to a reduction of necessary resources. This article reviews the possibilities and challenges arising from the use of laser diodes especially compared to current high-power LED systems in terms of efficiency, color-rendering properties, and thermal management.

Enhancing the conversion efficiency of extreme ultraviolet light sources using a 2 µm-wavelength laser

2021 ◽  
Author(s):  
Yun Yuan ◽  
Yan-Yun Ma ◽  
Wenpeng Wang ◽  
Shijia Chen ◽  
Ye Cui ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Emission Spectrum ◽  
Ultraviolet Light ◽  
Conversion Efficiency ◽  
Extreme Ultraviolet ◽  
Light Sources ◽  
Band Emission ◽  
Percentage Points ◽  
Hydrodynamic Code ◽  
Extreme Ultraviolet Light

Abstract In this study, we use the FLASH radiation hydrodynamic code and the FLYCHK atomic code to investigate the energy conversion and spectra associated with laser–Sn target interactions with 1 µm and 2 µm wavelength lasers. We found that the conversion efficiency (CE) reached as much as 3.38% with the 2 µm laser, which is 1.48 percentage points higher than the 1 µm laser (CE = 1.9%). In addition, we analyzed the contribution of dominant ionization states to the emission spectrum for both lasers. We observed that the growths of the out-of-band emission eventually led to a broadening of the spectrum, resulting in a reduction of SP for the 1 µm laser. By contrast, the emission main peaks were all centered near 13.5nm for the 2 µm laser, which is beneficial for efficient emission of light with a 13.5 nm wavelength (relevant for nanolithographic applications).

>25 Gbit/s LiFi with Dual Wavelength Emission, Eye-safe, Laser Based White Light Collimated and Fiber Delivered Light Sources

2021 ◽  
Author(s):  
James Raring ◽  
Changmin Lee ◽  
Mohamed Sufyan Islim ◽  
Sovan Das ◽  
Adrian Sparks ◽  
...  
Keyword(s):  
White Light ◽  
Dual Wavelength ◽  
Light Sources ◽  
Wavelength Emission

Searching for 3D effects in the optical, high spectral resolution emission spectrum of KELT-9b

2021 ◽  
Author(s):  
Lorenzo Pino ◽  
Matteo Brogi ◽  
Jean-Michel Désert ◽  
Emily Rauscher
Keyword(s):  
Emission Spectrum ◽  
Spectral Resolution ◽  
Planet Formation ◽  
Emission Spectra ◽  
Optical Emission ◽  
High Spectral Resolution ◽  
Optical Emission Spectrum ◽  
Hot Jupiters ◽  
Atmospheric Structure ◽  
3D Effects

<p>Ultra-hot Jupiters (UHJs; T<sub>eq</sub> ≥ 2500 K) are the hottest gaseous giants known. They emerged as ideal laboratories to test theories of atmospheric structure and its link to planet formation. Indeed, because of their high temperatures, (1) they likely host atmospheres in chemical equilibrium and (2) clouds do not form in their day-side. Their continuum, which can be measured with space-facilities, can be mostly attributed to H- opacity, an indicator of metallicity. From the ground, the high spectral resolution emission spectra of UHJs contains thousands of lines of refractory (Fe, Ti, TiO, …) and volatile species (OH, CO, …), whose combined atmospheric abundances could track planet formation history in a unique way. In this talk, we take a deeper look to the optical emission spectrum of KELT-9b covering planetary phases 0.25 - 0.75 (i.e. between secondary eclipse and quadrature), and search for the effect of atmospheric dynamics and three-dimensionality of the planet atmosphere on the resolved line profiles, in the context of a consolidated statistical framework. We discuss the suitability of the traditionally adopted 1D models to interprete phase-resolved observations of ultra-hot Jupiters, and the potential of this kind of observations to probe their 3D atmospheric structure and dynamics. Ultimately, understanding which factors affect the line-shape in UHJs will also lead to more accurate and more precise abundance measurements, opening a new window on exoplanet formation and evolution.</p>

Prospects for 4-laser white-light sources

2018 ◽  
Vol 66 (3) ◽  
pp. 271-280 ◽  
Author(s):  
Snjezana Soltic ◽  
Andrew N. Chalmers
Keyword(s):  
White Light ◽  
Light Sources

scholarly journals Nanophosphors-Based White Light Sources

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1048 ◽  
Author(s):  
Maura Cesaria ◽  
Baldassare Di Bartolo
Keyword(s):  
Rare Earth ◽  
White Light ◽  
Volume Ratio ◽  
Light Sources ◽  
Co Doping ◽  
New Class ◽  
Luminescence Efficiency ◽  
Metal Doped ◽  
The Individual ◽  
The Impact

Miniaturization requests and progress in nanofabrication are prompting worldwide interest in nanophosphors as white-emission mercury-free lighting sources. By comparison with their bulk counterparts, nanophosphors exhibit reduced concentration quenching effects and a great potential to enhance luminescence efficiency and tunability. In this paper, the physics of the nanophoshors is overviewed with a focus on the impact of spatial confinement and surface-to-volume ratio on the luminescence issue, as well as rare earth-activated multicolor emission for white light (WL) output. In this respect, the prominently practiced strategies to achieve WL emission are single nanophosphors directly yielding WL by means of co-doping and superposition of the individual red, green, and blue emissions from different nanophosphors. Recently, a new class of efficient broadband WL emitting nanophosphors has been proposed, i.e., nominally un-doped rare earth free oxide (yttrium oxide, Y2O3) nanopowders and Cr transition metal-doped garnet nanocrystals. In regard to this unconventional WL emission, the main points are: it is strictly a nanoscale phenomenon, the presence of an emitting center may favor WL emission without being necessary for observing it, and, its inherent origin is still unknown. A comparison between such an unconventional WL emission and the existing literature is presented to point out its novelty and superior lighting performances.

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