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1.
Infrared optical absorption has been used to study OH−impurities into congruent co-doped LiNbO3:Cr3+:ZnO crystals doped with different Zn2+ concentration. The OH− IR absorption spectra present three bands that can be associated with different OH− complex centres available in the lattice. For crystals with lower Zn2+ concentrations (<4.7%) only one IR absorption band centred at 2867 nm (3490 cm−1) is reported which is associated with the OH− unperturbed vibration. For crystals with higher Zn2+ concentrations (>4.7%), two new bands associated with OH−vibration in distortion environment are reported. These bands are centred at 2827 nm (3537 cm−1) and 2847 nm (3512 cm−1) and can be associated with OH−-Zn2+ and Cr3+(Li+)-OH−-Zn2+(Int.) complex centres, respectively. Electron paramagnetic resonance (EPR) has been used to identify the Cr3+ centres in the lattice of the doped LiNbO3:ZnO crystals. 相似文献
2.
The thermoluminescence and photostimulated thermoluminescence of X-ray coloured NaCl crystals has been studied, together with the thermal annealing of F, F′ and M centres. Three glow peaks centred at 315, 341 and 348°K are obtained in the temperature range 300–400°K. The first peak (315°K) is ascribed to electron trapping by Cu2+ centres formed by X-irradiation. The other peaks (314 and 348°K) are related to the thermal annealing of M and F centres, respectively. 相似文献
3.
4.
M.O. Ramírez D. Jaque J.A. Sanz García L.E. Bausá J.E. Muñoz Santiuste 《Applied physics. B, Lasers and optics》2003,77(6-7):621-623
An optimization of the laser action performance from a diode-pumped Yb3+-doped LiNbO3:MgO crystal has been carried out. In this sense, efficient laser action at 1.06 m when pumping with a fiber-coupled laser diode at 980 nm has been demonstrated, achieving laser slope efficiencies as high as 74%. The influence of output mirror transmittance on both pumping threshold and laser slope efficiency has been investigated, and the parameters of relevance in laser dynamics (emission cross section and optical losses) have been determined. Under the experimental conditions leading to maximum slope efficiency, the pump power at threshold was 300mW, and the pump-to-laser conversion efficiency was 40%. PACS 42.55.Xi; 42.55.Rz; 42.60.Lh 相似文献
5.
Y.?Tan C.?Zhang F.?ChenEmail author F.-Q.?Liu D.?Jaque Q.-M.?Lu 《Applied physics. B, Lasers and optics》2011,103(4):837-840
We report on the generation of continuous wave lasers at a wavelength of ∼1064 nm in a Nd:YAG ceramic waveguide at room temperature.
The waveguide was fabricated by using 6 MeV carbon ion implantation at a fluence of 3×1014 ions/cm2. Laser operation has been realized with a slope efficiency as high as ∼11%. The pump threshold of an 808-nm laser beam for
the waveguide laser oscillation is 19.5 mW. 相似文献
6.
E. Cruz Z A. Negr n A. Ramos A S. Ramos B J. Hern ndez A F Jaque H. Murrieta S 《Radiation Physics and Chemistry》2001,61(3-6):443-444
The amount of the first stage coloration in KCl1−xBrx doped with Pb2+ has been investigated as a function of the dose rate and impurity concentration. For a dose rate of 12.88 kGy/h, the F color center production was independent of the quantity of Pb2+, and varied according to the ratio KCl/KBr. At a proportion of 50% of each halogen the typical stages were observed. However, if the dose rate is less than 3.22 kGy/h, the coloration production depends on the quantity of Pb2+. 相似文献
7.
The 1,3 intramolecular hydrogen transfer reaction in free thymine and in Mg(II)-thymine have been studied at the density functional theory level. The mechanism of intramolecular proton transfer in these systems emerges from the analysis of the reaction force profile along the reaction path; it is rationalized in terms of structural and electronic reorganizations that take place during the chemical transformation. Results show that the presence of Mg(II) monocoordinated to thymine activates the hydrogenic motion by inducing structural and electronic changes in the molecular backbone. In the metallic complex, it is found that the hydrogen transfer is followed by a relaxation process that facilitates the metal cation migration to form a bicoordinated complex. 相似文献
8.
E. Camarillo H. Murrieta J.M. Hernandez R. Zoilo M.C. Flores T.P.J. Han F. Jaque 《Journal of luminescence》2008,128(5-6):747-750
Lithium niobate (LiNbO3) crystals doped with chromium ions show a clear green colouring reflecting the absorption profile of the dominating [Cr]Li defect centres. A significant change in its colouration takes place when it is co-doped with other valency impurities such as Mg2+, Sc3+ and W6+, above a certain threshold concentration. This concentration singularity has been attributed to the formation of [Cr]Nb centres coexisting with the [Cr]Li centres.In this work, we extended the investigation on the effect of co-dopant ions in Cr:LiNbO3 to tetravalent cation such as GeO2. A singularity in the relative intensity of the 4A2→4T1 and 4A2→4T2 absorption band was observed for a concentration of ~1.5 mol%, compared with 4.5 mol% for Mg2+. The photoluminescence emission spectra also reveal a new emission band, at a lower energy than the [Cr]Li centre, corresponding to this threshold concentration. A charge compensation model is proposed to explain the role of cation impurities and results are compared with those of other valence impurities. 相似文献
9.
P. Haro-González I. R. Martin F. Lahoz S. González-Pérez N. E. Capuj D. Jaque 《Applied Physics A: Materials Science & Processing》2008,93(4):977-981
Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method
and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by
the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select
positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions.
The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical
properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show
that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has
been completed. 相似文献
10.
Pablo Jaque Alejandro Toro-Labb Peter Politzer Paul Geerlings 《Chemical physics letters》2008,456(4-6):135-140
We have explored the relationships between the reaction force F(ξ), the reaction force constant κ(ξ) and the projected force constants of the intramolecular proton transfer HO−NS → ON−SH along the intrinsic reaction coordinate ξ. The structural changes and energetics associated with the reaction are analyzed in terms of the three regions defined by F(ξ): reactant, transition and product. The significance of the similarity between κ(ξ) and the variation of the force constant associated to the reaction coordinate mode, kξ(ξ), is discussed in detail. 相似文献