Role of Charge Transfer Transition Mechanism behind Photodarkening in Yb doped silica fibers
24 Oct 2011-Vol. 1391, Iss: 1, pp 197-199
TL;DR: In this paper, the spectral characteristics of photodarkening of Yb doped fibers with different concentration and host composition have been presented in order to investigate how charge transfer transition acts as the mechanism behind photoderarkening effect.
Abstract: The spectral characteristics of photodarkening of Yb doped fibers with different concentration and host composition have been presented in order to investigate how Charge Transfer Transition acts as the mechanism behind Photodarkening effect.
TL;DR: AMP in combination with CAA and CAP can be used as a CO2 absorbent and buffering agent for the sequestration of CO2 in porous CaCO3.
Abstract: One aspect of the attempt to restrain global warming is the reduction of the levels of atmospheric CO2 produced by fossil fuel power systems This study attempted to develop a method that reduces CO2 emissions by investigating the absorption of CO2 into sterically hindered amine 2-amino-2-methyl-1-propanol (AMP), the acceleration of the absorption rate by using the enzyme carbonic anhydrase (CA), and the conversion of the absorption product to stable carbonates CO2 absorbed by AMP is converted via a zwitterion mechanism to bicarbonate species; the presence of these anions was confirmed with 1H and 13C NMR spectral analysis The catalytic efficiency (kcat/Km), CO2 absorption capacities, and enthalpy changes (ΔHabs) of aqueous AMP in the presence or absence of CA were found to be 261 × 106 or 135 × 102 M–1 s–1, 097 or 096 mol/mol, and −69 or −67 kJ/mol, respectively The carbonation of AMP-absorbed CO2 was performed by using various Ca2+ sources, viz, CaCl2 (CAC), Ca(OOCCH3)2 (CAA), and Ca(OOCCH2CH3)2
TL;DR: The findings are important to explain induced optical losses (photodarkening) in high-power fiber lasers.
Abstract: A broad visible luminescence band and characteristic IR luminescence of Yb3+ ions are observed under UV excitation in ytterbium-doped aluminosilicate glass. Samples made under both oxidizing and reducing conditions are analyzed. A strong charge-transfer absorption band in the UV range is observed for glass samples containing ytterbium. Additional absorption bands are observed for the sample made under reducing conditions, which are associated with f-d transitions of divalent ytterbium. The visible luminescence band is attributed to 5d-4f emission from Yb2+ ions, and the IR luminescence is concluded to originate from a relaxed charge-transfer transition. The findings are important to explain induced optical losses (photodarkening) in high-power fiber lasers.
19 Feb 2009
TL;DR: In this paper, the location of the charge transfer absorption band is strongly compositiondependent and is correlated to the valence stability of the ytterbium ion in the silicate glass matrix.
Abstract: In this paper we present how charge transfer processes influences the induced optical losses (photodarkening) in ytterbium doped fiber lasers. The location of the charge transfer absorption band is strongly composition dependent and is correlated to the valence stability of the ytterbium ion in the silicate glass matrix. An improved photodarkening performance can in general be observed for a charge-transfer band shifted to shorter wavelengths, although other routes are also possible to reduce photodarkening. Other parameters that affect the laser performance, such as absorption and emission cross section, must also be considered.
06 May 2007
TL;DR: In this paper, it was shown that divalent ytterbium ions are present in Yb2+ ion doped aluminosilicate glass, which may influence the formation of induced color centers in ybbium doped fiber lasers leading to reduced performance.
Abstract: We show that divalent ytterbium ions are present in ytterbium doped aluminosilicate glass. The presence of Yb2+-ions may influence the formation of induced color centers in ytterbium doped fiber lasers leading to reduced performance.