| 1. |
- Amari, Atia, et al.
(författare)
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Towards an efficient atomic frequency comb quantum memory
- 2010
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 130:9, s. 1579-1585
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Konferensbidrag (refereegranskat)abstract
- We present an efficient photon-echo experiment based on atomic frequency combs [Phys. Rev. A 79 (2009) 052329]. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr3+ -doped Y2SiO5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters. (c) 2010 Elsevier B.V. All rights reserved.
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| 2. |
- Bano, Nargis, et al.
(författare)
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Depth-resolved cathodoluminescence study of zinc oxide nanorods catalytically grown on p-type 4H-SiC
- 2010
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Ingår i: Journal of Luminescence. - : Elsevier Science B.V., Amsterdam.. - 0022-2313 .- 1872-7883. ; 130:6, s. 963-968
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Tidskriftsartikel (refereegranskat)abstract
- Optical properties of ZnO nanorods (NRs) grown by vapour-liquid-solid (VLS) technique on 4H-p-SiC substrates were probed by cathodoluminescence (CL) measurements at room temperature and at 5 K complemented with electroluminescence. At room temperature the CL spectra for defect related emission intensity was enhanced with the electron beam penetration depth. We observed a variation in defect related green emission along the nanorod axis. This indicates a relatively poor structural quality near the interface between ZnO NRs and p-SiC substrate. We associate the green emission with oxygen vacancies. Analysis of the low-temperature (5 K) emission spectra in the UV region suggests that the synthesized nanorods contain shallow donors and acceptors.
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| 3. |
- Basiev, T. T., et al.
(författare)
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Luminescent nanophotonics and advanced solid state lasers
- 2013
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 133, s. 233-243
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Tidskriftsartikel (refereegranskat)abstract
- In this review, authors present their latest findings in luminescence quenching kinetics theory and advanced solid state laser experiments. Luminescence quenching kinetics is a popular and exceptionally useful tool to analyze the nanosized luminophores and laser material nanostructure. Quenching kinetics may be multistage, some stages having a complex, not exponential, form. It is often the case for modern laser materials, which are nanostructurized, and for particular cases of energy transfer (such as cooperative down-conversion). We present compact and easy-to-use analytical expressions and computer simulation for various cases of nonexponential quenching kinetics: migration-accelerated quenching in bulk material; cooperative luminescence quenching in bulk material; and two extreme cases of energy transfer in nanoparticles - static and with superfast migration (both including cooperative case of luminescence quenching in ensembles of acceptors comprised of two-, three-, and more particles). We also review the most perspective laser experiments lately performed in our laboratory, including those on fluoride laser nanoceramics and materials for middle infra-red lasers. (c) 2011 Elsevier B.V. All rights reserved.
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| 4. |
- Basieva, Irina, et al.
(författare)
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Static cooperative luminescence quenching in nanoparticles
- 2014
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 151, s. 88-92
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Tidskriftsartikel (refereegranskat)abstract
- In nanoparticles (NPs) static quenching of luminescence may be slower than in bulk media due to the space restrictions on acceptor location. Many-body cooperative quenching (manifesting itself as, e.g., down-conversion) occurs when the donor energy is transferred to two-, three-, or more particles (a cooperative acceptor) at once. Random distribution of acceptor particles in diluted media accounts for the non-exponential form of the kinetics. When the analytical expression for the kinetics form is known, it can be fitted to the experiment in order to find various micro- and macro-quenching parameters of the luminescent material. In this paper, we present an analytical law for cooperative quenching kinetics in NPs at longer time. Its clear and compact form reflects the fact that, on average, donors located on the surface of NPs are the last to decay having acceptors on one side only. We compared the resulting formula with the Monte-Carlo computer simulation, and they show good agreement. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
- Khranovskyy, Volodymyr, et al.
(författare)
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Luminescence anisotropy of ZnO microrods
- 2012
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 132:10, s. 2643-2647
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Tidskriftsartikel (refereegranskat)abstract
- The local features of light emission from ZnO microrods were studied: it is revealed that ZnO luminescence spectra are significantly influenced by the crystal morphology. It is shown that the near and edge ultraviolet emission occurs primarily from the top (0001) planes of ZnO microrods; while the defect related visible emission was found to occur dominantly from the side facets. The room temperature cathodoluminescence analysis revealed that visible emission consists of a few overlapping peaks, arising due to recombination on common points and surface defects (Zn-i, V-o, V-o(O)/V-o(**) V-o(**) and surface defects.). While at low temperature, only the luminescence due to neutral donor bound exciton ((DX)-X-0) emission is observed. The data obtained suggest that the light emission spectra of ZnO material of diverse morphology cannot be directly compared, although some common spectral features are present.
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| 6. |
- Maeztu, Raquel, et al.
(författare)
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Chemiluminescence of phthalhydrazide derivatives in organized media : Interactions with surfactants and cyclodextrins
- 2011
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 131:4, s. 662-668
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Tidskriftsartikel (refereegranskat)abstract
- The chemiluminescent oxidation of some phthalhydrazide derivatives, luminol (LUM), isoluminol (ISOL), N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), has been carried out in micellar media and in the presence of natural cyclodextrins (CDs), using Co(II) as catalyst and H2O2 as oxidant. The cationic cetyltrimethylammonium bromide (CAB) and, in a lesser extent, the anionic sodium dodecyl sulfate (SDS) produce quenching in the chemiluminescence (CL) of all the luminophores at concentrations above the cmc, whereas slight enhancements are attained with the nonionic pentaethylene glycol monododecyl ether (C12E5). On the contrary, the incorporation of the CDs to the reaction produces a remarkable intensification of the CL. Binding of the luminophores to the macrocycles and the micelles has been studied by Pulsed-Gradient-Spin-Echo-NMR (PGSE-NMR) and fluorescence anisotropy. The cationic CTAB decreases the emission mainly due to charge compensation as a result of the association of the luminophores and the luminescent intermediates to the micelles. The presence of the alkyl substituents of ABEI and AHEI provides an additional hydrophobic contribution to the binding process. SDS quenches this reaction as the micelles retain Co(II) on their anionic layer. The protection and stabilization of these luminophores or their luminescent intermediates provided by the cavities of the CDs make this family of cyclic oligosaccharides much more suitable agents than the surfactants for enhancing the CL in aqueous media for this specific reaction.
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| 7. |
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| 8. |
- Serrano, Diana, et al.
(författare)
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Impact of the ion-ion energy transfer on quantum computing schemes in rare-earth doped solids
- 2014
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 151, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the Ce3+-Pr3+:Y2SiO5 emission spectra obtained under selective excitation of the two Ce3+ sites in Y2SiO5 and we show clear evidence of direct energy transfer from Ce3+ to Pr3+. Energy transfer microparameters were calculated from the experimental spectral overlap between the Ce3+ emission and the Pr3+ and Eu3+ absorptions from which, the transfer mechanisms Ce3+-> Pr3+ are concluded to be more efficient than the transfer mechanisms Ce3+-> Eu3+. The energy transfer processes demonstrated here are potentially detrimental for an efficient qubit readout, using Ce3+ as readout ion, as they lead to a quenching of the Ce3+ luminescence and can give rise to the unwanted change of Pr3+ and Eu3+ qubit states. The quantum computing readout scheme is based on permanent electric dipole interactions scaling as R-3, where R is the distance between the Ce3+ and the qubit ion. The non-radiative energy transfer processes also depend on the ion-ion distances, however as R-6. A discussion about the microscopic dopant distributions leading to an efficient single-ion readout quantum computing scheme is here presented. The likely existence of energy transfer paths between the qubits or, as in this case, between the readout ion and the qubit ions, has not been taken into account so far by the rare-earth based quantum computing approaches. The results of this study suggest the need to consider them in order to design realistic and efficient quantum computing schemes for rare-earth doped solids. (C) 2014 Elsevier B.V. All rights reserved.
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| 9. |
- Sun, Jianwu W., et al.
(författare)
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Comparative micro-photoluminescence investigation of ZnO hexagonal nanopillars and the seeding layer grown on 4H-SiC
- 2012
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 132:1, s. 122-127
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Tidskriftsartikel (refereegranskat)abstract
- We report on a comparative micro-photoluminescence investigation of ZnO hexagonal nanopillars (HNPs) and the seeding layer grown on the off-axis 4H-SiC substrate. Transmission electron microscope (TEM) results establish that a thin seeding layer continuously covers the terraces of 4H-SiC prior to the growth of ZnO HNPs. Low temperature photoluminescence (LTPL) shows that ZnO HNPs are only dominated by strong donor bound exciton emissions without any deep level emissions. Micro-LTPL mapping demonstrates that this is specific also for the seeding layer. To further understand the recombination mechanisms, time-resolved micro-PL spectra (micro-TRPL) have been collected at 5 K and identical bi-exponential decays have been found on both the HNPs and seeding layer. Temperature-dependent TRPL indicates that the decay time of donor bound exciton is mainly determined by the contributions of non-radiative recombinations. This could be explained by the TEM observation of the non-radiative defects in both the seeding layer and HNPs, like domain boundaries and dislocations, generated at the ZnO/SiC interface due to biaxial strain.
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| 10. |
- Yang, Jia-Xiang, et al.
(författare)
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Facile synthesis, optical properties and theoretical calculation of two novel two-photon absorption chromophores
- 2010
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 130:4, s. 654-659
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Tidskriftsartikel (refereegranskat)abstract
- Two heterocycle-based derivatives that can be used as two-photon absorption chromophore, 9-butyl-3-(2,6-diphenylpyridin-4-yl)-9H-carbazole (BDPYC) and 9-butyl-3-(4-(2, 6-diphenylpyridin-4-yl)styryl)-9H-carbazole (BDPSC) have been successfully synthesized and fully characterized by elemental analysis, IR, H-1 NMR, C-13 NMR and MS. The molecules possess D-pi-A structures, but have different pi bridge. The 9-butylcarbazole is used as a donor (D), and the pyridine ring is used as an acceptor (A). One- and two-photon absorption and excited fluorescence properties in various solvents were experimentally investigated. Two-photon initiated optical data recording experiments have been carried Out under 740 nm laser radiation, and the possible mechanism of optical data storage is discussed based on theoretical calculations.
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