| 1. |
- Denker, Boris, et al.
(author)
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Luminescent and laser properties of Yb-Er:GdCa4O(BO3)3 : a new crystal for eye-safe 1.5-µm lasers
- 2004
-
In: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 79:5, s. 577-581
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Journal article (peer-reviewed)abstract
- We present for the first time 1.5-μm laser emission in Yb-Er:GdCa 4O(BO3)3 (GdCOB). The crystals were grown by the Czochralski method from platinum crucibles. Spectroscopic and laser tests of the crystals are described. A continuous-wave output power of 80 mW was achieved in a monolithic microchip cavity under laser-diode pumping.
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| 2. |
- Hellström, Jonas, et al.
(author)
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Passive Q-switching at 1.54 µm of an Er-Yb:GdCa4O(BO3)3 laser with a Co2+:MgAl2O4 saturable absorber
- 2005
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In: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 81:1, s. 49-52
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Journal article (peer-reviewed)abstract
- We report, for the first time to our knowledge, efficient passive Q-switching of the 1.54-μm laser transition in an Er-Yb-doped crystalline medium. The laser configuration is a compact microchip design that is suitable for a range of practical applications such as range finding and lidar. The slope efficiency of 11.6%, pulse duration of 5-6 ns and average output power of 88 mW are all comparable with standard Er-Yb:glass lasers.
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| 3. |
- Acharya, B., et al.
(author)
-
Uncertainty quantification for proton-proton fusion in chiral effective field theory
- 2016
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 760, s. 584-589
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Journal article (peer-reviewed)abstract
- We compute the S-factor of the proton-proton (pp) fusion reaction using chiral effective field theory (chi EFT) up to next-to-next-to-leading order (NNLO) and perform a rigorous uncertainty analysis of the results. We quantify the uncertainties due to (i) the computational method used to compute the pp cross section in momentum space, (ii) the statistical uncertainties in the low-energy coupling constants of chi EFT, (iii) the systematic uncertainty due to the chi EFT cutoff, and (iv) systematic variations in the database used to calibrate the nucleon-nucleon interaction. We also examine the robustness of the polynomial extrapolation procedure, which is commonly used to extract the threshold S-factor and its energy-derivatives. By performing a statistical analysis of the polynomial fit of the energy-dependent S-factor at several different energy intervals, we eliminate a systematic uncertainty that can arise from the choice of the fit interval in our calculations. In addition, we explore the statistical correlations between the S-factor and few-nucleon observables such as the binding energies and point-proton radii of H-2,H-3 and He-3 as well as the D-state probability and quadrupole moment of H-2, and the beta-decay of 3H. We find that, with the state-of-the-art optimization of the nuclear Hamiltonian, the statistical uncertainty in the threshold S-factor cannot be reduced beyond 0.7%.
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| 4. |
- Dettenrieder, Carina, et al.
(author)
-
Determination of volatile organic compounds in water by attenuated total reflection infrared spectroscopy and diamond-like carbon coated silicon wafers
- 2020
-
In: Chemosensors. - : MDPI. - 2227-9040. ; 8:3, s. 1-17
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Journal article (peer-reviewed)abstract
- Volatile organic compounds (VOCs) are one of the most commonly detected contaminants in water. The occurrence is mainly in gasoline and other petroleum-based products, fumigants, paints and plastics. Releases into the environment and the widespread use have an impact on the ecosystem such as humans and animals due to their toxicity, mutagenicity, and carcinogenicity. VOCs may persist in groundwater and may enter drinking water supplies. In this paper, a diamond-like carbon (DLC)-coated silicon waveguide in combination with a polymer film (ethylene/propylene copolymer, E/P-co) for enrichment of analytes was investigated to determine its suitability for ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopic detection of VOCs. The DLC film was fluorine-terminated enhancing the adhesion of the hydrophobic polymer to the waveguide surface. The analytes diffuse into the hydrophobic polymer whereas water is excluded from the emanating evanescent field. Therefore, direct detection in aqueous systems is enabled. Nine VOCs, i.e., ethylbenzene (EB), trichloroethylene (TCE), tetrachloroethylene (TeCE), the xylene isomers (p-xylene, pXYL; m-xylene, mXYL; o-xylene, oXYL), naphthalene (NAPH), toluene (TOL), and benzene (BENZ), were evaluated simultaneously qualitatively and quantitatively showing the potential of DLC coatings revealing high sensitivities in the low ppb to ppm concentration range, i.e., 50 ppb for TeCE. To the best of our knowledge, this is the first time of IR spectroscopic detection of VOCs in aqueous solutions using DLC-coated waveguides in combination with a hydrophobic polymer. By utilizing a DLC-coated waveguide, a versatile sensor for real-time monitoring in harsh environments such as effluents, leaking pipelines, and underground storage tanks is feasible due to response times within a few minutes.
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| 5. |
- Ekstrom, A., et al.
(author)
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Accurate nuclear radii and binding energies from a chiral interaction
- 2015
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 91:5
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Journal article (peer-reviewed)abstract
- With the goal of developing predictive ab initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLOsat, yield accurate binding energies and radii of nuclei up to Ca-40, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective J(pi) = 3(-) states in O-16 and 40Ca are described accurately, while spectra for selected p- and sd-shell nuclei are in reasonable agreement with experiment.
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| 6. |
- Ekstrom, A., et al.
(author)
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Statistical uncertainties of a chiral interaction at next-to-next-to leading order
- 2015
-
In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 42:3
-
Journal article (peer-reviewed)abstract
- We have quantified the statistical uncertainties of the low-energy coupling-constants (LECs) of an optimized nucleon-nucleon interaction from chiral effective field theory at next-to-next-to-leading order. In addition, we have propagated the impact of the uncertainties of the LECs to two-nucleon scattering phase shifts, effective range parameters, and deuteron observables.
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| 7. |
- Ekström, Andreas, et al.
(author)
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Effects of Three-Nucleon Forces and Two-Body Currents on Gamow-Teller Strengths
- 2014
-
In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 113:26, s. 262504-
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Journal article (peer-reviewed)abstract
- We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems and compute Gamow-Teller transitions in C14 and O22,24 using consistent two-body currents. We compute spectra of the daughter nuclei N14 and F22,24 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2≈0.84–0.92 of the axial-vector coupling. The half-life of C14 depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.
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| 8. |
- Forssen, Christian, 1974, et al.
(author)
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Large-scale exact diagonalizations reveal low-momentum scales of nuclei
- 2018
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In: Physical Review C. - 2469-9985 .- 2469-9993. ; 97:3
-
Journal article (peer-reviewed)abstract
- Ab initio methods aim to solve the nuclear many-body problem with controlled approximations. Virtually exact numerical solutions for realistic interactions can only be obtained for certain special cases such as few-nucleon systems. Here we extend the reach of exact diagonalization methods to handle model spaces with dimension exceeding 10(10) on a single compute node. This allows us to perform no-core shell model (NCSM) calculations for Li-6 in model spaces up to N-max = 22 and to reveal the He-4+d halo structure of this nucleus. Still, the use of a finite harmonic-oscillator basis implies truncations in both infrared (IR) and ultraviolet (UV) length scales. These truncations impose finite-size corrections on observables computed in this basis. We perform IR extrapolations of energies and radii computed in the NCSM and with the coupled-cluster method at several fixed UV cutoffs. It is shown that this strategy enables information gain also from data that is not fully UV converged. IR extrapolations improve the accuracy of relevant bound-state observables for a range of UV cutoffs, thus making them profitable tools. We relate the momentum scale that governs the exponential IR convergence to the threshold energy for the first open decay channel. Using large-scale NCSM calculations we numerically verify this small-momentum scale of finite nuclei.
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| 9. |
- Haas, Julian, et al.
(author)
-
Infrared Spectroscopy Based on Broadly Tunable Quantum Cascade Lasers and Polycrystalline Diamond Waveguides
- 2018
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 143:21, s. 5112-5119
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Journal article (peer-reviewed)abstract
- Recently emerging broadly tunable quantum cascade lasers (tQCL) emitting in the mid-infrared (MIR) are a versatile alternative to well established thermal emitters in combination with interferometers as applied in Fourier transform infrared (FTIR) spectroscopy. The wide and highly spectrally resolved wavelength tuning characteristics along with superior spectral energy density renders laser-based vibrational spectroscopy methods an efficient alternative vs. conventional molecular spectroscopies. Using diamond in attenuated total reflection (ATR) sensing formats benefits from the physical robustness and chemical resistivity of the internal reflective element (IRE) material. While inherent material absorption frequently limits the optical path length within diamond ATR elements, the herein presented design combining bright tQCLs with a multi-reflection polycrystalline diamond (PCD) ATR element enables an optical beam path length of approximately 5 cm. Thereby, sensitive spectroscopic measurements in the MIR are enabled. As an example, non-invasive glucose monitoring in human saliva is examined, highlighting the potential benefits of the proposed analytical concept with regards to exquisite sensitivity and selectivity in combination with a robust sensing interface, i.e., diamond. This approach paves the way towards directly analyzing molecular constituents in complex and potentially corrosive biomedical and biochemical matrices.
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| 10. |
- Haas, Julian, et al.
(author)
-
Polycrystalline diamond thin-film waveguides for mid-infrared evanescent field sensors
- 2018
-
In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 3:6, s. 6190-6198
-
Journal article (peer-reviewed)abstract
- Photonic design and optimization of thin-film polycrystalline diamond waveguides are shown, serving as advanced evanescent field transducers in the mid-infrared fingerprint regime (2000-909 cm(-1); 5-11 mu m). Design constraints inherent to optical/system considerations and the material were implemented in a finite element method (FEM)-based simulation method that allowed three-dimensional modeling of the overall structure. Thus, lateral mode confinement, attenuation in the direction of radiation propagation, and physical resilience were evaluated. In a final step, the designed structures were fabricated, and their utility in combination with a broadly tunable external cavity quantum cascade laser for chemical sensing of a liquid phase analyte was demonstrated.
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