| 11. |
- Murayama, A, et al.
(author)
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Transfer dynamics of spin-polarized excitons into semiconductor quantum dots
- 2009
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In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 129, s. 1927-1930
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Journal article (peer-reviewed)abstract
- We study on the transfer dynamics of spin-polarized excitons into self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of ZnMnSe through a ZnSe barrier layer. A variation in the degree of circular polarization P of excitonic photoluminescence in the coupled QDs was observed between samples with different thicknesses (LB) of the non-magnetic barrier. Relatively high values of P (0.3) were obtained in the samples with LB=1 or 2 nm, and the time dependences of the P value indicate the spin-transfer dynamics. From the LB dependence of the spin-transfer time, the spin-transfer mechanism is discussed, namely spin-conserving energy transfer.
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| 12. |
- Palm, V., et al.
(author)
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Single-molecule linewidths of terrylene in incommensurate biphenyl: Thermocycling and time-resolved experiments
- 2007
-
In: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 127:1, s. 218-223
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Journal article (peer-reviewed)abstract
- The purely electronic linewidth delta of terrylene impurity molecules in monocrystalline biphenyl is studied at temperatures T between 1.7 and 3.5 K using the technique of single-molecule spectroscopy (SMS). Based on the data obtained, individual molecules appear to have their own law of delta(T) dependence; further, hysteresis effects have been observed in thermocycling experiments. The single-molecule (SM) lines investigated quickly broaden and vanish at temperatures between 3 and 3.5 K and reappear after the sample is cooled down again. At T approximate to 2 K, a slow process of spectral diffusion (SD) was observed on timescales longer than 10s. To learn about the role of faster SD processes, the technique of intensity time-frequency correlation (ITFC) SMS was applied to a stable SM line after it had been broadened by 75% as a result of a thermocycling experiment. At 2 and 2.3 K, no significant line broadening could be revealed on timescales between 0.16 ms and 10s. (C) 2007 Elsevier B.V. All rights reserved.
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| 13. |
- Pitois, C., et al.
(author)
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Lanthanide-cored fluorinated dendrimer complexes : synthesis and luminescence characterization
- 2005
-
In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 111:4, s. 265-283
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Journal article (peer-reviewed)abstract
- Eu3+-. Tb3+- and Er3+-cored dendrimer complexes were prepared by self-assembly of three fluorinated dendrons, each with a carboxylate anion focal point, around the lanthanide ion. Energy transfer from the peripheral fluorinated phenyl moieties of the dendrons to the lanthanide cation was evidenced spectroscopically for Eu3+- and Tb3+-cored dendrimer complexes in solution. The excitation of perfluorinated aromatic groups was found to decay with ca. 0.7 ns and a longer decay time 10-13 ns was related to the coordination at the Ln(3+) focal point. Luminescence from the lanthanide core decays with lifetime in the range 1-1.5ms over a wide concentration range (mu M-mM), similar to the luminescence decay time of the corresponding acetate ion complexes in D2O. The main quenching mechanism of the lanthanide emission appears to be due to vibrations among surrounding C-H bonds of the intermediate shell of the flexible dendrimer scaffold. Antenna effect and energy harvesting from the surface of the dendrimer and transfer to the core was the main mechanism for luminescecnce in the dendrimer complexes with lanthanide cations.
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| 14. |
- Rebane, A, et al.
(author)
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Quantum interference between multi photon absorption pathways in organic solid
- 2007
-
In: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 127:1, s. 28-33
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Journal article (peer-reviewed)abstract
- We demonstrate spatial interference fringe pattern by simultaneous one- and three-photon absorption of UV and near-IR femitosecond pulses in thin film organic solid at room temperature. We use organic dendrimers that are specially designed to have strong fluorescence and very large three-photon absorption cross-section. High fringe visibility allows the quantum interference to be observed by eye. (C) 2007 Elsevier B.V. All rights reserved.
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| 15. |
- Stafström, Sven
(author)
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Dynamical simulation of exciton dissociation in poly(para-phenylenevinylene) systems
- 2005
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In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 112:01-Apr, s. 357-362
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Journal article (peer-reviewed)abstract
- We report results from simulations of field-induced exciton dissociation in poly(para-phenylenevinylene) (PPV). The simulations were performed by solving the time-dependent Schrodinger equation and the lattice equation of motion simultaneously and non-adiabatically. The electronic system and the coupling of the electrons to the lattice were described by an extended three-dimensional version of the Su-Schrieffer-Heeger (SSH) model. The dissociation time is shown to depend strongly on the field strength as well as on the excitation energy and the lattice energy. The separation process is highly non-adiabatic and involves a significant rearrangement of the electron distribution. (c) 2004 Elsevier B.V. All rights reserved.
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| 16. |
- Sychugov, Ilya, et al.
(author)
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Structural imaging of a Si quantum dot: Towards combined PL and TEM characterization
- 2006
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In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 121:2, s. 353-
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Journal article (peer-reviewed)abstract
- Individual silicon quantum dots were fabricated by electron-beam lithography, plasma etching and a two-step oxidation process. This enables photoluminescence (PL) from individual dots at various temperatures to be detected and spectrally resolved using a sensitive charge-coupled device camera-imaging system, as reported previously. The regular array-like arrangement of oxidized pillars containing individual nanocrystals, in principle, enables combined transmission electron microscopy (TEM) and low-temperature PL characterization of the same Si quantum dot. To this end, a technique employing focused ion beam was developed for preparation of the pillar/nanocrystal of interest for TEM. It is shown that silicon quantum dots of several nanometers in size can be characterized using such a method.
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| 17. |
- Vanin, E. V., et al.
(author)
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Broadband photoluminescence from pulsed laser deposited Er2O3 films
- 2006
-
In: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 121:2, s. 256-258
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Journal article (peer-reviewed)abstract
- Photoluminescence (PL) with the bandwidth of 45 nm (1523-1568 nm, at the level of 3 dB) was observed in amorphous Er2O3 films grown on to the quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula to determine the dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient of 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. In 5.7mm-long waveguide amplifier a theory predicts the spectral gain of 20dB with 1.4dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er3+ ions are excited from the ground state to the I-4(13/2) laser level. Strong broadband PL at room temperature and inherently flat spectral gain promise Er2O3 films for ultra-short high-gain optical waveguide amplifiers and integrated light circuits.
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| 18. |
- Xu, Huailiang, et al.
(author)
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Upconversion dynamics in Er3+-doped YAG
- 2005
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In: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 111:3, s. 191-198
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Journal article (peer-reviewed)abstract
- Green, blue, violet and ultraviolet upconversion luminescence is reported at room temperature in a YAG: 10.5% Er3+ crystal pumped by one-colour (647 nm) and two-colour (647 + 618 nm) laser excitation. The upconversion mechanism was studied by means of time-resolved luminescence spectroscopy and the energy flow pathways are described. Based on the results it appears that energy transfer upconversion is the dominant contribution to the upconverted luminescence upon 647 nm excitation, and excited state absorption is the dominating mechanism upon 647 + 618 nm excitation.
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| 19. |
- Zhao, Ming, et al.
(author)
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Strain-symmetrized Si/SiGe multi-quantum well structures grown by molecular beam epitaxy for intersubband engineering
- 2006
-
In: Journal of luminescence. - : Elsevier BV. - 0022-2313. ; 121:2, s. 403-408
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Journal article (peer-reviewed)abstract
- Three strain-symmetrized Si/SiGe multi-quantum well structures, designed for probing the carrier lifetime of intrawell intersubband transitions between heavy hole 1 (HH1) and light hole 1 (LH1) states with transition energies below the optical phonon energy, were grown by molecular beam epitaxy at low temperature on fully relaxed SiGe virtual substrates. The grown structures were characterized by using various experimental techniques, showing a high crystalline quality and very precise growth control. The lifetime of the LH1 excited state was determined directly with pump-probe spectroscopy. The measurements indicated an increase of the lifetime by a factor of 2 due to the increasingly unconfined LH1 state, which agreed very well with the design. It also showed a very long lifetime of several hundred picoseconds for the holes excited out of the well to transit back to the well through a diagonal process.
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