| 1. |
- Giuliani, G., et al.
(författare)
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Round-Robin Measurements of Linewidth Enhancement Factor of Semiconductor Lasers in COST 288 Action
- 2007
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Ingår i: Lasers and Electro-Optics, 2007 and the International Quantum Electronics Conference. CLEOE-IQEC 2007. European Conference on. - 1424409306 - 9781424409303 ; , s. 4385967-
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Konferensbidrag (refereegranskat)abstract
- Round-robin measurements on the linewidth enhancement factor are carried out in many laboratories participating to EU COST 288 Action. Up to 7 different techniques are applied to DFB, VCSELs, QCL, and QD lasers, and results are compared.
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| 2. |
- Nelander, Rikard, et al.
(författare)
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Fingerprints of spatial charge transfer in Quantum Cascade Lasers
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102, s. 1-113104
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Tidskriftsartikel (refereegranskat)abstract
- We show that mid-infrared transmission spectroscopy of a quantum cascade laser provides clear-cut information on changes in charge location at different bias. Theoretical simulations of the evolution of the gain/absorption spectrum for a lambda~7.4 µm InGaAs/AlInAs/InP quantum cascade laser have been compared with the experimental findings. Transfer of electrons between the ground states in the active region and the states in the injector goes hand in hand with a decrease of discrete intersubband absorption peaks and an increase of broad, high-energy absorption toward the continuum delocalized states above the barriers.
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| 3. |
- Pereira, M. F., Jr., et al.
(författare)
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Characterization of intersubband devices combining a nonequilibrium many body theory with transmission spectroscopy experiments
- 2007
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Ingår i: Journal of Materials Science: Materials in Electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 18:7, s. 689-694
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we apply a microscopic nonequilibrium many body Keldysh Green's functions approach to an analysis of complex intersubband optical materials and devices. The calculated absorption/gain spectra are in very good agreement with transmission spectroscopy measurements of quantum cascade laser structures operating in the mid-infrared (midIR). The very good agreement reached between theoretical results and experimental measurements benchmarks the predictive power of our algorithms and its potential as a design tool for efficient intersubband designs.
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| 4. |
- Revin, D.G., et al.
(författare)
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Probing the electronic and optical properties of quantum cascade lasers under operating conditions
- 2006
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. ; 6386, s. 1-63860
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report the realisation of spectroscopic broadband transmission experiments on quantum cascade lasers (QCLs) under continuous wave operating conditions for drive currents up to laser threshold. This technique allows, for the first time, spectroscopic study of light transmission through the waveguide of QCLs in a very broad spectral range (λ~1.5-12 μm), limited only by the detector response and by interband absorption in the materials used in the QCL cladding regions. Waveguide transmittance spectra have been studied for both TE and TM polarization, for InGaAs/InAlAs/InP QCLs with different active region designs emitting at 7.4 and 10μm. The transmission measurements clearly show the depopulation of the lower laser levels as bias is increased, the onset and growth of optical amplification at the energy corresponding to the laser transitions as current is increased towards threshold, and the thermal filling of the second laser level and decrease of material gain at high temperatures. This technique also allows direct determination of key parameters such as the exact temperature of the laser core region under operating conditions, as well as the modal gain and waveguide loss coefficients.
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| 5. |
- Heydarkhan-Hagvall, Sepideh, 1969, et al.
(författare)
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DNA microarray study on gene expression profiles in co-cultured endothelial and smooth muscle cells in response to 4- and 24-h shear stress
- 2006
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Ingår i: Molecular and cellular biochemistry. - : Springer Science and Business Media LLC. - 0300-8177 .- 1573-4919. ; 281:1-2, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Shear stress, a major hemodynamic force acting on the vessel wall, plays an important role in physiological processes such as cell growth, differentiation, remodelling, metabolism, morphology, and gene expression. We investigated the effect of shear stress on gene expression profiles in co-cultured vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Human aortic ECs were cultured as a confluent monolayer on top of confluent human aortic SMCs, and the EC side of the co-culture was exposed to a laminar shear stress of 12 dyn/cm(2) for 4 or 24 h. After shearing, the ECs and SMCs were separated and RNA was extracted from the cells. The RNA samples were labelled and hybridized with cDNA array slides that contained 8694 genes. Statistical analysis showed that shear stress caused the differential expression (p < or = 0.05) of a total of 1151 genes in ECs and SMCs. In the co-cultured ECs, shear stress caused the up-regulation of 403 genes and down-regulation of 470. In the co-cultured SMCs, shear stress caused the up-regulation of 152 genes and down-regulation of 126 genes. These results provide new information on the gene expression profile and its potential functional consequences in co-cultured ECs and SMCs exposed to a physiological level of laminar shear stress. Although the effects of shear stress on gene expression in monocultured and co-cultured EC are generally similar, the response of some genes to shear stress is opposite between these two types of culture (e.g., ICAM-1 is up-regulated in monoculture and down-regulated in co-culture), which strongly indicates that EC-SMC interactions affect EC responses to shear stress.
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| 6. |
- Ceponkus, J, et al.
(författare)
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A simple model for the water o-H-2 complex
- 2006
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 124:2
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Tidskriftsartikel (refereegranskat)abstract
- The infrared spectrum of the complex between o-H-2 and H2O, D2O, or HDO, isolated in a matrix of solid p-H-2, has been studied between 20 and 4500 cm(-1). In addition the infrared spectrum of the complex between p-D-2 and H2O in solid o-D-2 has been studied. The spectral shifts are interpreted as the result of the quadrupole-dipole interaction between hydrogen and water. (c) 2006 American Institute of Physics.
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| 7. |
- Ceponkus, J, et al.
(författare)
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Intermolecular vibrations of different isotopologs of the water dimer: Experiments and density functional theory calculations.
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:19
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Tidskriftsartikel (refereegranskat)abstract
- Far infrared spectra of seven different isotopologs of the water dimer have been measured in neon matrices at 2.8 K. The experiments are interpreted with the aid of density functional theory calculations, in particular the calculated harmonic isotopic shifts were utilized. All six intermolecular vibrational modes of the water dimer and the fully deuterated water dimer are assigned based the isotopic shifts induced. 31 of a total of 42 intermolecular fundamental modes of the seven different H, D, and (18)O containing water dimers have been experimentally observed and assigned accordingly. The overall agreement between the calculations and the experiments of all isotopologs results in a complete and consistent description of these modes.
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| 8. |
- Sablinskas, V, et al.
(författare)
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A high-resolution FT-IR study of the fundamental bands v(7), v(8), and v(18) of ethene secondary ozonide
- 2005
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:39, s. 8719-8723
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Tidskriftsartikel (refereegranskat)abstract
- Ozonization reaction of ethene in neat film at 77 K was performed. Separation of ethene secondary ozonide from the other products of the reaction was performed by continuous pumping of the reactor. Only the products, which evaporated from the walls of the reactor at 185 K, were transferred to the gas cell. The high-resolution infrared absorption spectrum of gaseous ethene secondary ozonide (C2H4O3) in a static gas long-path absorption cell has been recorded in the 900-1100 cm(-1) spectral region at 185 K. The spectral resolution was 0.003 cm(-1). Analyses of the nu(7)(A) band at 1037.0 cm(-1), the nu(8)(A) band at 956.1 cm(-1), and the nu(18)(B) band at 1082.1 cm(-1) have been performed using the Watson Hamiltonian model (A, reduction; IIIr, representation). A set of ground-state rotational and quartic centrifugal distortion constants have been obtained, and upper state spectroscopic constants have been determined for the bands investigated. A local resonance observed in vis is explained as c-Coriolis interaction with nu(10) + nu(11).
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