| 1. |
- Chen, W, et al.
(författare)
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Pressure dependence of Mn2+ fluorescence in ZnS:Mn2+ nanoparticles
- 2000
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Ingår i: Journal of Luminescence. - 0022-2313. ; 91:3-4, s. 139-145
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Tidskriftsartikel (refereegranskat)abstract
- The photoluminescence of Mn2+ in ZnS : Mn2+ nanoparticles with an average size of 4.5 nm has been measured under hydrostatic pressure from 0 to 6 GPa. The emission position is red-shifted at a rate of −33.3±0.6 meV/GPa, which is in good agreement with the calculated value of −30.4 meV/GPa using the crystal field theory.
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| 2. |
- Mohan, R. K., et al.
(författare)
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Photon-echo amplification and regeneration for optical data storage and processing
- 2000
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Ingår i: Journal of Luminescence. - 0022-2313. ; 86:3-4, s. 383-390
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Tidskriftsartikel (refereegranskat)abstract
- Optical data storage devices and erasable memories with storage densities in the range of terabits/cm2, all-optical devices for communication like optical bit-rate converters, routers and image processors can become a reality with photon-echo-based frequency-selective materials. In photon-echo-based optical data storage and data processing the photon-echo-output intensity generally is about 0.1–1% of the input intensity. Many devices, such as processors would require that the photon-echo output is used as an input to a new photon-echo process and hence the amplification of photon-echo signals is necessary. In this paper we describe the development of a fibre amplifier for amplifying photon-echo data. Requirements and performance for the fibre amplifier are discussed. Some examples of our initial experiments, where photon-echoes amplified by the fibre amplifier are used to generate secondary photon-echoes, are also presented.
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| 3. |
- Nagirnyi, V, et al.
(författare)
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Separation of excitonic and electron-hole processes in metal tungstates
- 2003
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Ingår i: Journal of Luminescence. - 0022-2313. ; 102, s. 597-603
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Tidskriftsartikel (refereegranskat)abstract
- Absorption, reflection and emission polarization spectra of CdWO4 crystals have been studied in the region 3.5-30 eV in order to distinguish the excitonic and electron-hole processes in the vicinity of the band gap. The following parameters have been defined from the Urbach tail study at 6-300 K: E-0 = 5 eV, sigma(0) = 0.31, homega = 70 meV (565 cm(-1)). Excitonic processes have been shown to dominate at excitation of tungstate crystals in the lower part of the conduction band. Excitons are formed due to the transitions into the tungstate W5d states hybridized with O6p and possess a very strong tendency for self-trapping. Free electrons and holes can be created at the energies 1-2 eV (depending on the crystal) higher than the bottom of the conduction band due to the transitions into cationic states. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 4. |
- Robert-Philip, I., et al.
(författare)
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Generation of non-classical light by single quantum dots
- 2003
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Ingår i: Journal of Luminescence. - 0022-2313. ; 102-103:SPEC, s. 67-71
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Konferensbidrag (refereegranskat)abstract
- The emission statistics of single semiconductor quantum dots is investigated in view of generating quantum states of light. Correlation experiments show that the emission of a quantum dot can be regulated so as to produce only one photon at a time as well as correlated photon pairs. This observation opens the way to the use of semiconductor quantum dots as triggered sources of single photons, which could find applications in quantum cryptography. We then discuss the potentiality of quantum dots for the production of mutually coherent single photons as well as entangled photons that could be used in quantum information processing schemes. © 2002 Elsevier Science B.V. All rights reserved.
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| 5. |
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| 6. |
- Monemar, B, et al.
(författare)
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Magnetic properties of bound hole states for complex neutral defects in semiconductors
- 1986
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 36:3, s. 149-159
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of an electron-hole pair bound to complex neutral defects in semiconductors are discussed and compared to experimental data for both direct- and indirect-bandgap materials. The properties of bound hole states for such defects are discussed in a general formalism, which avoids the generally inadequate effective-mass-like description often used in previous literature. In the case of low symmetry defects with a dominantly hole-attractive local potential the primary bound hole state is often nondegenerate and shows a spin-like character with a quenched angular momentum. This case has recently been demonstrated experimentally for a large number of defects in GaP and Si. A strong spin-orbit interaction may inhibit such a quenching so that the bound hole angular momentum is at least partly retained. This situation often prevails for complex defects in materials like CdTe and ZnTe, where the valence band spin-orbit splitting Δso is large. For electron-attractive central cell potentials, the bound hole state is generally effective-mass-like, and retains its anisotropic magnetic behaviour due to the hole angular momentum. Experimental data supporting this situation are also demonstrated, for both Si and compound semiconductors.
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| 7. |
- Sendova-Vassileva, M, et al.
(författare)
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Depth dependence of photoluminescence and chemical bonding in porous silicon
- 1999
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Ingår i: Journal of Luminescence. - 0022-2313 .- 1872-7883. ; 80:1-4, s. 179-182
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Tidskriftsartikel (refereegranskat)abstract
- Porous silicon (PS) is studied by stepwise peeling of the surface layer to clarify the non-uniformity in the photoluminescence (PL) and correlate it with the in-depth chemical bonding and structure of the 30 μm thick layer. The PL intensity grows by an order of magnitude after the peeling off of the first 10 μm and decreases five times in the next 5 μm while the peak maximum position shifts from 730 to 800 nm. X-ray photoelectron spectroscopy (XPS) measurements show that Si–Si and Si–O bonds are present both on the surface and below, and the preferential oxidation state of silicon changes from 3+ and 4+ on the surface to 1+ and 2+ below 10 μm. Using Raman spectroscopy silicon nanocrystals are shown to exist. Their mean size can be estimated at about 3 nm. These results show that the strongest PL comes from a region in the PS layer where silicon nanocrystallites are surrounded by oxides with a low level of oxidation and not from the strongly oxidized surface layer.
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| 8. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Investigation of the effect of engine lubricant oil on remote temperature sensing using thermographic phosphors
- 2016
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 179, s. 568-573
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Tidskriftsartikel (refereegranskat)abstract
- Phosphor thermometry, a remote temperature sensing technique, is widely implemented to measure the temperature of different combustion engines components. The presence of engine lubricant can influence the behavior of the applied sensor materials, known as thermographic phosphors, and thus leading to erroneous temperature measurements. The effect of two engine lubricants on decay times originating from six different thermographic phosphors was investigated. The decay time of each thermographic phosphor was investigated as a function of lubricant/phosphor mass ratio. Tests were conducted at temperatures around 293 K and 376 K for both lubricants. The investigations revealed that ZnO:Zn and ZnS:Ag are the only ones that exhibit a change of the decay time as function of the lubricant/phosphor mass ratio. While the remaining thermographic phosphors, namely BaMg2Al16O27:Eu (BAM), Al2O3-coated BaMg2Al16O27:Eu, La2O2S:Eu, Mg3F2GeO4:Mn, displayed no sensitivity of their characteristic decay time on to the presence of lubricant on the porous coating. Biases in the calculated temperature are to be expected if the utilized thermographic phosphor displays decay time sensitivity to the existence of the engine lubricant within the sensor. Such distortions are concealed and can occur undetected leading to false temperature readings for the probed engine component.
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| 9. |
- 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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| 10. |
- Arapan, Sergiu, et al.
(författare)
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Exciton levels and optical absorption in coupled double quantum well structures
- 2005
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 112:1-4, s. 216-219
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Tidskriftsartikel (refereegranskat)abstract
- We study exciton states in a coupled double quantum well (CDQW) semiconductor structure. Exciton levels and binding energies of direct and indirect excitons are calculated for a symmetric CDQW system with an applied electric field. The exciton states are obtained by solving the exciton effective-mass equation in the momentum space using the modified Gaussian quadrature method. Within this approach we perform realistic calculations of the exciton states by taking into account the coupling between different subband pairs and calculate optical-absorption coefficients. The calculated values of the exciton binding energy are in a good agreement with the experiment and the calculated absorption spectra qualitatively agree with the measured photoluminescence excitation spectra.
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