| 1. |
- Andersson-Engels, Stefan, et al.
(författare)
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Deep-tissue optical imaging and photoactivation activities at biophotonics@tyndall
- 2016
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Ingår i: Frontiers in Optics, FiO 2016. - 2162-2701. - 9781943580194
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Konferensbidrag (refereegranskat)abstract
- Activities for deep tissue imaging and photoactivation will be presented. Wihin Biophotonics@Tyndall projects based on upconverting nanoparticles and ultrasound optical tomography will be pursued. Data from collaborative research will be given.
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| 2. |
- Bengtsson, Alexander, et al.
(författare)
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Characterization and modeling of acousto-optic signal strengths in highly scattering media
- 2019
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 10:11, s. 5565-5584
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound optical tomography (UOT) is an imaging technique based on the acousto-optic effect that can perform optical imaging with ultrasound resolution inside turbid media, and is thus interesting for biomedical applications, e.g. for assessing tissue blood oxygenation. In this paper, we present near background free measurements of UOT signal strengths using slow light filter signal detection. We carefully analyze each part of our experimental setup and match measured signal strengths with calculations based on diffusion theory. This agreement between experiment and theory allows us to assert the deep tissue imaging potential of similar to 5 cm for UOT of real human tissues predicted by previous theoretical studies [Biomed. Opt. Express 8, 4523 (2017)] with greater confidence, and indicate that future theoretical analysis of optimized UOT systems can be expected to be reliable. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 3. |
- Bott, Lukas Thomas, et al.
(författare)
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Coulomb dissociation of O-16 into He-4 and C-12
- 2023
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Ingår i: NUCLEAR PHYSICS IN ASTROPHYSICS - X, NPA-X 2022. - : EDP Sciences. - 2100-014X. ; 279
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Konferensbidrag (refereegranskat)abstract
- We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4.
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| 4. |
- Gunther, Jacqueline, et al.
(författare)
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Deep tissue imaging with acousto-optical tomography and spectral hole burning with slow light effect : A theoretical study
- 2018
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Ingår i: Journal of Biomedical Optics. - 1083-3668. ; 23:7
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Tidskriftsartikel (refereegranskat)abstract
- Biological tissue is a highly scattering medium that prevents deep imaging of light. For medical applications, optical imaging offers a molecular sensitivity that would be beneficial for diagnosing and monitoring of diseases. Acousto-optical tomography has the molecular sensitivity of optical imaging with the resolution of ultrasound and has the potential for deep tissue imaging. Here, we present a theoretical study of a system that combines acousto-optical tomography and slow light spectral filters created using spectral hole burning methods. Using Monte Carlo simulations, a model to obtain the contrast-to-noise ratio (CNR) deep in biological tissue was developed. The simulations show a CNR > 1 for imaging depths of ∼5 cm in a reflection mode setup, as well as, imaging through ∼12 cm in transmission mode setups. These results are promising and form the basis for future experimental studies.
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| 5. |
- Gunther, Jacqueline, et al.
(författare)
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Theoretical study of combined acousto-optical tomography and slow light filters
- 2018
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Ingår i: Optical Tomography and Spectroscopy, OTS 2018. - 9781557528209 ; Part F90-OTS 2018
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Konferensbidrag (refereegranskat)abstract
- Monte Carlo simulations were used to determine the contrast-to-noise ratio of acoustooptical tomographic imaging with slow light filters versus possible imaging depth. Both reflection and transmission setups were considered. The theoretical model showed that imaging through 12 cm of breast tissue could be plausible.
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| 6. |
- Walther, Andreas, et al.
(författare)
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Analysis of the potential for non-invasive imaging of oxygenation at heart depth, using ultrasound optical tomography (UOT) or photo-acoustic tomography (PAT)
- 2017
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 8:10, s. 4523-4536
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Tidskriftsartikel (refereegranskat)abstract
- Despite the important medical implications, it is currently an open task to find optical non-invasive techniques that can image deep organs in humans. Addressing this, photo-acoustic tomography (PAT) has received a great deal of attention in the past decade, owing to favorable properties like high contrast and high spatial resolution. However, even with optimal components PAT cannot penetrate beyond a few centimeters, which still presents an important limitation of the technique. Here, we calculate the absorption contrast levels for PAT and for ultrasound optical tomography (UOT) and compare them to their relevant noise sources as a function of imaging depth. The results indicate that a new development in optical filters, based on rare-earth-ion crystals, can push the UOT technique significantly ahead of PAT. Such filters allow the contrastto- noise ratio for UOT to be up to three orders of magnitude better than for PAT at depths of a few cm into the tissue. It also translates into a significant increase of the image depth of UOT compared to PAT, enabling deep organs to be imaged in humans in real time. Furthermore, such spectral holeburning filters are not sensitive to speckle decorrelation from the tissue and can operate at nearly any angle of incident light, allowing good light collection. We theoretically demonstrate the improved performance in the medically important case of non-invasive optical imaging of the oxygenation level of the frontal part of the human myocardial tissue. Our results indicate that further studies on UOT are of interest and that the technique may have large impact on future directions of biomedical optics.
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| 7. |
- Afzelius, Mikael, et al.
(författare)
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Demonstration of Atomic Frequency Comb Memory for Light with Spin-Wave Storage
- 2010
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Ingår i: Physical Review Letters. - 1079-7114. ; 104:4
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Tidskriftsartikel (refereegranskat)abstract
- We present a light-storage experiment in a praseodymium-doped crystal where the light is mapped onto an inhomogeneously broadened optical transition shaped into an atomic frequency comb. After absorption of the light, the optical excitation is converted into a spin-wave excitation by a control pulse. A second control pulse reads the memory (on-demand) by reconverting the spin-wave excitation to an optical one, where the comb structure causes a photon-echo-type rephasing of the dipole moments and directional retrieval of the light. This combination of photon-echo and spin-wave storage allows us to store submicrosecond (450 ns) pulses for up to 20 mu s. The scheme has a high potential for storing multiple temporal modes in the single-photon regime, which is an important resource for future long-distance quantum communication based on quantum repeaters.
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| 8. |
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| 9. |
- Alqedra, Mohammed K., et al.
(författare)
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Optical coherence properties of Kramers' rare-earth ions at the nanoscale for quantum applications
- 2023
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Ingår i: Physical Review B. - 2469-9950. ; 108:7
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Tidskriftsartikel (refereegranskat)abstract
- Rare Earth (RE) ion doped nanomaterials are promising candidates for a range of quantum technology applications. Among RE ions, the so-called Kramers' ions possess spin transitions in the GHz range at low magnetic fields, which allows for high-bandwidth multimode quantum storage, fast qubit operations as well as interfacing with superconducting circuits. They also present relevant optical transitions in the infrared. In particular, Er3+ has an optical transition in the telecom band, while Nd3+ presents a high-emission-rate transition close to 890 nm. In this paper, we measure spectroscopic properties that are of relevance to using these materials in quantum technology applications. We find the inhomogeneous linewidth to be 10.7 GHz for Er3+ and 8.2 GHz for Nd3+, and the excited state lifetime T1 to be 13.68 ms for Er3+ and 540μs for Nd3+. We study the dependence of homogeneous linewidth on temperature for both samples, with the narrowest linewidth being 379 kHz (T2=839 ns) for Er3+ measured at 3 K, and 62 kHz (T2=5.14μs) for Nd3+ measured at 1.6 K. Further, we investigate time-dependent homogeneous linewidth broadening due to spectral diffusion and the dependence of the homogeneous linewidth on magnetic field to get additional clarity of mechanisms that can influence the coherence time. In light of our results, we discuss two applications: single qubit-state readout and a Fourier-limited single photon source.
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| 10. |
- 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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| 11. |
- Barmann, P, et al.
(författare)
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Spatially and temporally resolved electron density measurements in streamers in dielectric liquids
- 1997
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 30:5, s. 856-863
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Tidskriftsartikel (refereegranskat)abstract
- Spatially and temporally resolved spectroscopic measurements of light emitted from positive streamers in transformer oil are presented. Analyses of the measurements performed with a DC needle-plane gap yield electron densities and indications of the atomic excitation temperatures in the streamers. The hydrogen emission reveals an electron density below 10(16) cm(-3) during the main part of the streamer propagation time (80-90%). Later the light is also characterized by emission from a high-density plasma with electron densities in the range 10(18)-10(19) cm(-3). The electron density during this time increases approximately linearly with distance from the initiation point and a density factor of four higher has been measured at the streamer tip than at the root. Measurements with high spectral resolution detect both high and low electron densities simultaneously. A tentative model of the interior of the streamer plasma, spatially resolved, is presented.
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| 12. |
- Barmann, P, et al.
(författare)
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Spectroscopic measurements of streamer filaments in electric breakdown in a dielectric liquid
- 1996
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 29:5, s. 1188-1196
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Tidskriftsartikel (refereegranskat)abstract
- Emission spectroscopy has been utilized to provide information about the electron density and temperature in streamers and breakdown arcs in transformer oil. Recorded spectra include strongly broadened hydrogen Balmer-alpha lines and vibration/rotation band profiles of the C-2 molecule. The origin of the observed broadening of hydrogen lines is discussed and it is concluded that it arises mainly from collisions with charged particles, so-called dynamic Stark broadening. By assuming that the broadening is due solely to dynamic Stark broadening, electron densities between 1 x 10(18) and 1 x 10(19) cm(-3) were obtained for the rear of positive streamer filaments during the later stages of propagation. For negative streamers we obtained an upper limit of 3 x 10(16) cm(-3) and for breakdown arcs electron densities up to 4 x 10(18) cm(-3). The temperature information in the C-2 emission profiles and the intensity ratio of the hydrogen Balmer lines are discussed. Rough estimations of the temperature are presented both for positive and for negative streamers.
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| 13. |
- Bartholomew, John G., et al.
(författare)
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High-resolution spectroscopic techniques for studying rare-earth ions in nanoparticles
- 2023
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 257
-
Tidskriftsartikel (refereegranskat)abstract
- Rare-earth doped nanoparticles can exhibit narrow optical and spin linewidths at low temperatures. These outstanding properties for nanomaterials make them attractive for quantum technologies based on optically addressable spins such as quantum memories and computers. Although accurate linewidth measurements have been reported using, for example, spectral hole burning or photon echo techniques, so far they have been mostly restricted to large ensembles of particles. Being able to extend linewidths measurements to few and single particles is particularly important in view of their integration in nanophotonic devices. In this paper, we present techniques for determining inhomogeneous and homogeneous linewidths of small ensembles of rare-earth ions in doped nanoparticles with high signal-to-noise ratios for convenient integration times. Using these techniques we have observed property variations for particles from the same synthesis, a first step towards their optimization for applications in quantum technologies.
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| 14. |
- Belfrage, Christina, et al.
(författare)
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Doppler-Free Laser Spectroscopy Measurements on a Ne Discharge for Determination of 22Ne-20Ne Isotope Shifts
- 1983
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 27:5, s. 357-370
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Tidskriftsartikel (refereegranskat)abstract
- We have used Doppler-free polarization spectroscopy, intermodulated fluorescence and intermodulated optogalvanic spectroscopy for measuring isotope shifts in 6 Ne lines connecting the 2p53s and 2p53p configurations. The measurements were performed on two different hollow cathodes. For the 5852, 5882, 5945, 5976, 6143 and 6164 A lines the 22Ne-20Ne isotope shift was found to be 2300(15), 1740(2), 1717(3), 1728(5), 1669(4) and 1663(5) MHz, respectively. These results are in fair agreement with previous optical spectroscopy data.
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| 15. |
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| 16. |
- Bengtsson, Alexander, et al.
(författare)
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Comparison of contrast-to-noise ratios of different detection methods in ultrasound optical tomography
- 2022
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 13:9, s. 4834-4850
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound optical tomography (UOT) is a hybrid imaging modality based on interaction between ultrasound and light, with a potential to extend optical imaging capabilities in biological tissues to depths of several centimeters. Several methods have been developed to detect the UOT signal. To better understand their potential for deep tissue imaging, we present a theoretical contrast-to-noise comparison between the spectral hole burning, single-shot off-axis holography, speckle contrast, and photorefractive detection methods for UOT. Our results indicate that spectral hole burning filters have the potential to reach the largest imaging depths. We find that digital off-axis holography and photorefractive detection can have good contrast-to-noise ratio at significant depths. The speckle contrast method has a smaller penetration depth comparatively.
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| 17. |
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| 18. |
- Bengtsson, Magnus, et al.
(författare)
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Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators
- 2005
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Ingår i: Optics and Lasers in Engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 43:6, s. 624-632
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Tidskriftsartikel (refereegranskat)abstract
- Remote fluorescence imaging of fungal growth on polymeric high-voltage insulators was performed using a mobile lidar system with a laser wavelength of 355 nm. Insulator areas contaminated by fungal growth could be distinguished from clean surfaces and readily be imaged. The experiments were supported by detailed spectral studies performed in laboratory using a fibre-optic fluorosensor incorporating an optical multi-channel analyser system (OMA) and a nitrogen laser emitting radiation at 33 7 nm.
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| 19. |
- Bengtsson, Magnus, et al.
(författare)
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Fungus covered insulator materials studied with laser-induced fluorescence and principal component analysis
- 2005
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 59:8, s. 1037-1041
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Tidskriftsartikel (refereegranskat)abstract
- A method combining laser-induced fluorescence and principal component analysis to detect and discriminate between algal and fungal growth on insulator materials has been studied. Eight fungal cultures and four insulator materials have been analyzed. Multivariate classifications were utilized to characterize the insulator material, and fungal growth could readily be distinguished from a clean surface. The results of the principal component analyses make it possible to distinguish between algae infected, fungi infected, and clean silicone rubber materials. The experiments were performed in the laboratory using a fiber-optic fluorosensor that consisted of a nitrogen laser and an optical multi-channel analyzer system.
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| 20. |
- Bengtsson, Magnus, et al.
(författare)
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Lidar fluorescence measurements of algal growth on electrical insulators
- 2003
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Ingår i: 2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666). - 0780377346 ; , s. 473-473
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Konferensbidrag (refereegranskat)abstract
- Fluorescence measurements using lidar techniques have been shown to be useful for monitoring of algal growth on e.g. historical monuments. In this experiment similar measurements were performed on electrical insulators to examine the correlation between algal growth and the quality of the insulator, a factor of importance in the high-voltage grid management
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| 21. |
- Bengtsson, Magnus, et al.
(författare)
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Remote laser-induced breakdown spectroscopy for the detection and removal of salt on metal and polymeric surfaces
- 2006
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 60:10, s. 1188-1191
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Tidskriftsartikel (refereegranskat)abstract
- The detection of contamination such as salt in outdoor high-voltage insulator systems and its subsequent removal are vital for a reliable transmission of electric power. Remote detection of salt on a copper metal surface was carried out by using a mobile laser-induced breakdown spectroscopy (LIBS) Lidar system with a laser wavelength of 355 nm. Detection of salt on a polymeric high-voltage insulator was obtained when an additional lens was inserted into the beam path, and the number of photons that was detected could be calculated by using a calibrated white light source. Ablative cleaning could readily be carried out with LIBS and was verified by observing the disappearance of the sodium D-line emission.
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| 22. |
- Bengtsson, Per Erik, et al.
(författare)
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Rotational cars thermometry in sooting flames
- 1992
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 0010-2202 .- 1563-521X. ; 81:1-3, s. 129-140
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Tidskriftsartikel (refereegranskat)abstract
- Coherent anti-Stokes Raman scattering of pure rotational transitions, rotational CARS, is demonstrated as an efficient method for temperature determination in sooting flames. The dual broadband CARS approach was used to measure temperature profiles in premixed, sooting ethylene flames at atmospheric pressure by probing the nitrogen gas. The recorded spectra were of equally high quality in non-sooting and sooting flames with volume fractions of soot of up to 7 x 10 7 cm3 soot/cm3The advantages of rotational CARS in comparison with several other techniques for the measurement of temperatures in sooting flames, and the general applicability of the technique to different combustion conditions, are discussed. Potential limitations in the application of rotational CARS to sooting flames that are more heavily sooting than the ones investigated in this study, are outlined.
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| 23. |
- Bengtsson, Per-Erik, et al.
(författare)
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Vibrational CARS thermometry in sooty flames: Quantitative evaluation of C2 absorption interference
- 1990
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Ingår i: Combustion and Flame. - 0010-2180. ; 82:2
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Tidskriftsartikel (refereegranskat)abstract
- The application of nitrogen vibrational CARS thermometry to sooty, premixed, atmospheric pressure flames has been investigated using a Nd:YAG laser based system. It was found that laser-produced C2 radicals strongly absorb part of the fundamental band peak in the CARS spectrum. This was the most severe interference to the CARS signal. A quantitative investigation of temperature errors caused by the C2 absorption effect is presented. The correlation between the absorption interference and the soot volume fraction was examined for different flame conditions. Also, the increase of the nonresonant susceptibility in sooty flame regions is clearly illustrated and its effect on thev evaluated temperature is quantitatively determined. The single-shot temperature standard deviation has also been investigated in flames with different soot loadings. Finally, other interference effects to the CARS signals in sooty flames are described and discussed.
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| 24. |
- Bondza, Saskia, et al.
(författare)
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A simple experimental method for measuring the thermal sensitivity of single-mode fibers
- 2020
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 91:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple technique to experimentally determine the optical-path length change with temperature for optical single-mode fibers. Standard single-mode fibers act as natural low-finesse cavities, with the Fresnel reflection of the straight cleaved surfaces being ∼3%, for the laser light coupled to them. By measuring the intensity variations due to interference of light reflected from the fiber front and end surfaces, while ramping the ambient temperature, the thermal sensitivity of the optical-path length of the fiber can be derived. Light was generated by a narrow linewidth, low drift laser. With our fairly short test fibers, we found that it was possible to reach a relative precision of the temperature sensitivity, compared to a reference fiber, on the 0.4%-2% scale and an absolute precision of 2%-5%, with the potential to improve both by an order of magnitude. The results for single-acrylate, dual-acrylate, and copper- and aluminum-coated fibers are presented. Values are compared with analytic models and results from a finite element method simulation. With the aid of these measurements, a simple fiber-interferometer, which is insensitive to thermal drifts, could be constructed.
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| 25. |
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| 26. |
- Chaudhry, Nadia, et al.
(författare)
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Breast Cancer Diagnosis Using Extended-Wavelength–Diffuse Reflectance Spectroscopy (EW-DRS) : Proof of Concept in Ex Vivo Breast Specimens Using Machine Learning
- 2023
-
Ingår i: Diagnostics. - 2075-4418. ; 13:19, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to investigate the feasibility of using diffuse reflectance spectroscopy (DRS) to distinguish malignant breast tissue from adjacent healthy tissue, and to evaluate if an extended-wavelength range (450–1550 nm) has an advantage over the standard wavelength range (450–900 nm). Multivariate statistics and machine learning algorithms, either linear discriminant analysis (LDA) or support vector machine (SVM) are used to distinguish the two tissue types in breast specimens (total or partial mastectomy) from 23 female patients with primary breast cancer. EW-DRS has a sensitivity of 94% and specificity of 91% as compared to a sensitivity of 40% and specificity of 71% using the standard wavelength range. The results suggest that DRS can discriminate between malignant and healthy breast tissue, with improved outcomes using an extended wavelength. It is also possible to construct a simple analytical model to improve the diagnostic performance of the DRS technique.
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| 27. |
- Da Via, C, et al.
(författare)
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Lightwave Analogue Links For LHC Detector Front-ends
- 1994
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 344:1, s. 199-211
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Tidskriftsartikel (refereegranskat)abstract
- The requirements on optical links for transferring analog and digital signals from the detector front-ends to the readout electronics at future high-luminosity colliders are reviewed. The advantages of external modulation techniques are discussed. An outline is given of the the R&D programme recently started at CERN by a collaboration involving high-energy physics institutes, optoelectronics research laboratories and industry, in order to develop electro-optic intensity modulator arrays, particularly for analogue applications, and to investigate the feasibility of volume production. The design of multichannel demonstrators in lithium niobate and III-V semiconductor technology is described. Preliminary results of the performance measurements are presented.
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| 28. |
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| 29. |
- Dernfalk, Andreas, 1975, et al.
(författare)
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Laser-induced fluorescence spectroscopy for detection of biological contamination on composite insulators
- 2003
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Ingår i: In Proc. 13th International Symposium on High Voltage Engineering, Delft, Netherlands.
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Konferensbidrag (refereegranskat)abstract
- A new technique for remote detection of biological contamination on high-voltage outdoor insulators has been investigated. The technique, which is based on laser-induced fluorescence (LIF) spectroscopy, has been applied to study surfaces of real silicon rubber insulators from a distance of approximately 60 m. Measurements were performed outdoors on a number of clean, as well as, biologically contaminated insulators. Several types of biological contamination were included, as five of the studied insulators had become covered when installed in Sweden, and another three had been contaminated by fungal growth in laboratory. Fluorescence spectra obtained from the surfaces of the described insulators are presented and the applicability of the technique is discussed and compared with photographic methods.
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| 30. |
- Dyke, T.R., et al.
(författare)
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Experimental demonstration of data erasure for time-domain optical memories
- 1999
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 16:5, s. 805-811
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Tidskriftsartikel (refereegranskat)abstract
- Data erasure is considered an essential requirement for a practical optical time-domain memory, and it requires that the laser used have very good frequency stability. Such a laser is developed for this work, and data erasure is demonstrated with a sample of YSiO5:Eu3+ for write/rewrite pulse sequences of up to a duration of 100 μs. This is two orders of magnitude longer than had been achieved previously. Phase-sensitive detection is introduced and is shown to be invaluable for monitoring the write, rewrite, and read processes.
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| 31. |
- Elman, U., et al.
(författare)
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Influence of laser phase and frequency fluctuations on photon-echo data erasure
- 1996
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 13:9, s. 1905-1915
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Tidskriftsartikel (refereegranskat)abstract
- Erasure of data stored by use of photon echoes has been investigated as a function of data writing time and data storage time. The results clarify the requirements on laser phase and frequency stability for performing photon-echo data erasure. The analysis of phase and frequency stability of a light source by the photon-echo erasure process is illustrated. A theoretical analysis emphasizing the physical processes that affect the erasure efficiency as well as an extensive discussion of possible error sources are given. Finally, an approach to bit-selective photon-echo data erasure that is insensitive to laser phase and frequency fluctuations is suggested.
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| 32. |
- Elman, U., et al.
(författare)
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Statistical modeling and theoretical analysis of the influence of laser phase fluctuations on photon echo data erasure and stimulated photon echoes
- 1996
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Ingår i: Laser Physics. - 1054-660X. ; 6:4, s. 721-728
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Tidskriftsartikel (refereegranskat)abstract
- The effect of random laser phase fluctuations on stimulated photon echoes (SPEs) and on coherently added SPEs was studied and evaluated both experimentally and analytically with statistical methods. The general concept of describing laser frequency fluctuations as a stationary stochastic process is presented and applied to three specific SPE configurations. The effect of phase fluctuations on erasing an SPE by coherently adding another SPE, phase-shifted by 180 degrees relative to the first, is presented.
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| 33. |
- Fortese, Fabricio, 1976-
(författare)
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Early Determination of Arbitral Jurisdiction : Balancing efficacy, efficiency, and legitimacy of arbitration
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines the timing of judicial determination of jurisdictional disputes in the presence of an arbitration agreement. The analysis focuses on Article 8(1) of the UNCITRAL Model Law on International Commercial Arbitration (and Article II(3) of the New York Convention on the Recognition and Enforcement of Foreign Arbitral Awards). It circumscribes the discussions to a nuanced interpretative strategy.It is uncontroversial that national courts have the authority to decide, conclusively, disputes on arbitral jurisdiction. It is common ground that arbitrators, too, have the authority to rule on their own jurisdiction, subject to judicial control. This is known as the principle of competence-competence, which is widely recognised in arbitration legislation, institutional rules, and practice. The critical research question that this dissertation deals with is whether national courts should (or could) conclusively determine arbitral jurisdiction before or after the arbitrators have preliminarily determined that controversy.This dissertation does not question who has the authority to settle jurisdictional disputes (conflict of jurisdictions). The assumption is that both, judges and arbitrators, enjoy such decision-making power. Instead, this research is about when (timing) a court should exercise that authority with conclusive effects.This work examines and answers the when question from an autonomous legal-interpretation perspective, detached from a given State's law, concepts, and rules. Its theoretical framework is specific to the Model Law and national arbitration laws that have adopted it without deviating from it – at least not from the wording of Article 8.
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| 34. |
- Gobel, K., et al.
(författare)
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Coulomb dissociation of 16O into 4He and 12C
- 2020
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1668:1
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Konferensbidrag (refereegranskat)abstract
- We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision.
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| 35. |
- Goldner, Ph., et al.
(författare)
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Long coherence lifetime and electromagnetically induced transparency in a highly-spin-concentrated solid
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:3
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Tidskriftsartikel (refereegranskat)abstract
- We have studied a rare-earth-doped crystal, Pr3+:La-2(WO4)(3), which exhibits a high magnetic-moment density. Although the latter favors rare-earth dephasing, a nuclear-spin coherence lifetime of 250 mu s has been observed, as well as electromagnetically induced transparency (EIT). This suggests that a broad range of materials could be considered for quantum information applications such as quantum memories for light, where solids are especially attractive. Absorption and dispersion curves are independently in very good agreement with EIT theory. Fano-like profiles have also been observed.
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| 36. |
- Grafström, Peter, et al.
(författare)
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Hyperfine structure and isotope shift of highly excited barium-I states
- 1982
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Ingår i: Zeitschrift für Physik A Hadrons and Nuclei. - 0939-7922. ; 306:4, s. 281-284
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution laser-spectroscopy measurements of hyperfine structure and isotope shifts were performed for the 6snd 1 D 2 sequence of Ba-I in the regionn=12–24. Stepwise laser excitations of a collimated atomic beam were used. A strong influence on the hyperfine structure is observed at the perturbation atn=14, caused by interaction with the 5d7d configuration. Whereas the isotope shift for the even isotopes stays essentially constant with increasingn, the odd isotopes exhibit a strong change, indicating hyperfine-induced shifts. Interesting discussions with Prof. E. Matthias in the final stage of this work are gratefully acknowledged. This work was supported by the Swedish Natural Science Research Council.
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| 37. |
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| 38. |
- Guillot-Noel, O., et al.
(författare)
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Hyperfine structure and hyperfine coherent properties of praseodymium in single-crystalline La-2(WO4)(3) by hole-burning and photon-echo techniques
- 2009
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 79:15
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the hyperfine structure and hyperfine coherent properties of the H-3(4)(0)-> D-1(2)(0) transition of Pr3+ ions in a tungstate single crystal La-2(WO4)(3) by hole-burning and photon-echo techniques. This work is motivated by the search of an efficient three level Lambda system in this new compound with which we could build up a quantum memory. By nonconventional hole-burning experiments, the ordering of the hyperfine splittings in the H-3(4)(0) ground state and in the D-1(2)(0) excited state is obtained. The hyperfine splittings are thus ordered: 24.6 and 14.9 MHz for the H-3(4)(0) level and 5.0 and 7.3 MHz for the D-1(2)(0) level. The relative and absolute transition strengths of individual hyperfine transitions are determined by comparing absorption strengths and by measuring the Rabi flopping frequency as the transition is coherently driven. Free induction and Raman echo decays give inhomogeneous and homogeneous hyperfine linewidths of 57 +/- 2 and 1.25 +/- 0.1 kHz, respectively.
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| 39. |
- Guillot-Noel, O., et al.
(författare)
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Hyperfine structure, optical dephasing, and spectral-hole lifetime of single-crystalline Pr3+: La-2(WO4)(3)
- 2007
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 75:20
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the experiments related to quantum information applications, involving rare-earth doped inorganic crystals, are performed on yttrium orthosilicate single crystals. The work presented here is motivated by the search of new compounds which can be used in the field of quantum computing and/or quantum storage. Relaxation times and hyperfine structure of the H-3(4)(0)-> D-1(2)(0) transition in 1.4% Pr3+:La-2(WO4)(3) at 4 K have been measured by photon-echo and spectral-hole-burning techniques. The hyperfine splittings of the ground H-3(4)(0) and the excited D-1(2)(0) states are 14.9 +/- 0.1 MHz, 24.6 +/- 0.1 MHz and 5.0 +/- 0.1 MHz, 7.3 +/- 0.1 MHz, respectively. An inhomogeneous linewidth of 18.8 +/- 0.1 GHz was measured. A homogeneous linewidth of 25.3 +/- 2.0 kHz was obtained with or without an external magnetic field of about 14 mT. The fluorescence dynamics of the D-1(2) level obtained by a direct excitation in the H-3(4)-> D-1(2) transition gives a nonexponential decay which indicates energy-transfer processes. This decay can be accurately fitted by the Inokuti-Hirayama model [J. Chem. Phys. 43, 1978 (1965)] with a radiative lifetime of 61 +/- 1 mu s giving a minimal homogeneous linewidth of 2.6 kHz. The spectral-hole lifetime due to population redistribution within the ground hyperfine levels is 16 +/- 2 s. The results obtained for the La-2(WO4)(3) compound make this crystal an interesting host for quantum applications.
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| 40. |
- Hastings-Simon, S R, et al.
(författare)
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Spectral hole-burning spectroscopy in Nd3+: YVO4
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 77:12
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Tidskriftsartikel (refereegranskat)abstract
- We present spectral hole-burning measurements on the 879 nm, I-4(9/2) -> F-4(3/2) transition in Nd3+ : YVO4. We observe antiholes in the spectrum along with long lived spectral holes, which demonstrates optical pumping between the ground state Zeeman levels. The spectral holes are narrow (homogeneous linewidth of 63 kHz) at 2.1 K with a 300 mT applied magnetic field. We also perform preliminary spectral tailoring in this material by creating a 40 MHz wide transmission window in the inhomogeneous absorption. These results show the potential of the Zeeman levels in Nd doped materials to be used for spectral tailoring for quantum and classical information processing.
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| 41. |
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| 42. |
- Horvath, Sebastian P., et al.
(författare)
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Noise-free on-demand atomic frequency comb quantum memory
- 2021
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Ingår i: Physical Review Research. - 2643-1564. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- We present an extension of the atomic frequency comb protocol that utilizes the Stark effect to perform noise-free, on-demand, control. An experimental realization of this protocol was implemented in the Pr3+:Y2SiO5 solid-state system, and a recall efficiency of 38% for a 0.8 μs storage time was achieved. Experiments were performed with both bright pulses as well as weak-coherent states, the latter achieving a signal-to-noise ratio of 570±120 using input pulses with an average photon number of ∼0.1. The principal limitation for a longer storage time was found to be the minimum peak width attainable for Pr3+:Y2SiO5. We employ an adaptation of an established atomic frequency comb model to investigate an on-demand, wide-bandwidth, memory based on Eu3+:Y2SiO5. From this, we determine that a storage time as long as 100 μs may be practical even without recourse to spin-wave storage.
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| 43. |
- Jonsson, G, et al.
(författare)
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Hyperfine structure and radiative lifetimes in the 3s2n p2P3/2 sequence of Al-27 using time resolved laser spectroscopy
- 1984
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Ingår i: Zeitschrift für Physik A Hadrons and Nuclei. - 0939-7922. ; 316:3, s. 259-263
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Tidskriftsartikel (refereegranskat)abstract
- Using time-resolved laser spectroscopy we have determined the hyperfine structure in the 3s2n p2P3/2 sequence of27Al (I=5/2). The magnetic-dipole interaction constants were found to scale withn*-2.85 (n* is the effective principal quantum number) in the investigated regionn=6–12. Significant quadrupole interaction constants were obtained forn=6–9. The measured radiative lifetimes forn=6–12 scale withn*2.
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| 44. |
- Julsgaard, Brian, et al.
(författare)
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Understanding laser stabilization using spectral hole burning
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:18, s. 11444-11465
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Tidskriftsartikel (refereegranskat)abstract
- There have recently been several studies of the performance of laser frequency stabilization using spectral holes in solids, instead of an external cavity, as a frequency reference. Here an analytical theory for Pound-Drever-Hall laser frequency stabilization using spectral hole-burning is developed. The interaction between the atomic medium and the phase modulated light is described using a linearized model of the Maxwell-Bloch equations. The interplay between the carrier and modulation sidebands reveals significant differences from the case of locking to a cavity. These include a different optimum modulation index, an optimum sample absorption, and the possibility to lock the laser in an inherent linear frequency drift mode. Spectral holes in solids can be permanent or transient. For the materials normally used, the dynamics and time scales of transient holes often depend on population relaxation processes between ground state hyperfine levels. These relaxation rates can be very different for different solid state materials. We demonstrate, using radio-frequency pumping, that the hyperfine population dynamics may be controlled and tailored to give optimum frequency stabilization performance. In this way also materials with initially non-optimum performance can be used for stabilization. The theoretical predictions regarding the inherent linear frequency drift is compared to experimental data from a dye laser stabilized to a spectral hole in a Pr3+: Y2SiO5 crystal. (C) 2007 Optical Society of America.
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| 45. |
- Jönsson, G., et al.
(författare)
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Natural radiative lifetimes in the 3 sns 1S0 and 3 snd 1D2 sequences of magnesium
- 1984
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Ingår i: Physical Review A. ; A30:5, s. 2429-2432
-
Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes have been determined in the determined in the 3 sns 1S0 (n=4-15) and the 3 snd 1D2 (n=3-15) sequences of Mg I employing a pulsed-laser system. The radiative lifetimes in the 1S0 sequence and of the higher members in the 1D2 sequence are unperturbed and scale as (n*)2.6 (where n* is the effective principal quantum number), while the lifetimes of the lower members in the 1D2 sequence are perturbed by the doubly excited 3p2 configuration. The measured lifetimes are compared with available theoretical calculations, and a very good agreement is obtained.
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| 46. |
- Kalachev, Alexey, et al.
(författare)
-
Backward retrieval in optical quantum memory controlled by an external field
- 2008
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:4
-
Tidskriftsartikel (refereegranskat)abstract
- A scheme for backward retrieval in optical quantum memories in which information is stored in collective states of an extended resonant atomic ensemble is developed such that phase conjugation can be implemented by application of an external nonuniform electric (magnetic) field without use of coherent exciting pulses. The possibilities of realizing such a scheme using resonant solid-state materials are discussed.
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| 47. |
- Kalachev, Alexey, et al.
(författare)
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Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage
- 2006
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 74:2
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent control of collective spontaneous emission in an extended atomic ensemble resonantly interacting with single-photon wave packets is analyzed. A scheme for coherent manipulation of collective atomic states is developed such that superradiant states of the atomic system can be converted into subradiant ones and vice versa. Possible applications of such a scheme for optical quantum-state storage and single-photon wave packet shaping are discussed. It is shown that also in the absence of inhomogeneous broadening of the resonant line, single-photon wave packets with arbitrary pulse shape may be recorded as a subradiant state and reconstructed even although the duration of the wave packets is larger than the superradiant lifetime. Specifically the applicability for storing time-bin qubits, which are used in quantum cryptography, is analyzed.
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| 48. |
- Karlsson, Jenny, et al.
(författare)
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A confocal optical microscope for detection of single impurities in a bulk crystal at cryogenic temperatures
- 2016
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 87:3
-
Tidskriftsartikel (refereegranskat)abstract
- A compact sample-scanning confocal optical microscope for detection of single impurities below the surface of a bulk crystal at cryogenic temperatures is described. The sample, lens, and scanners are mounted inside a helium bath cryostat and have a footprint of only 19 × 19 mm. Wide field imaging and confocal imaging using a Blu-ray lens immersed in liquid helium are demonstrated with excitation at 370 nm. A spatial resolution of 300 nm and a detection efficiency of 1.6% were achieved.
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| 49. |
- Karlsson, Jenny, et al.
(författare)
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High-resolution transient and permanent spectral hole burning in Ce3+ : Y2SiO5 at liquid helium temperatures
- 2016
-
Ingår i: Physical Review B. - 1098-0121. ; 93:22
-
Tidskriftsartikel (refereegranskat)abstract
- We perform hole burning with a low-drift stabilized laser within the zero phonon line of the 4f-5d transition in Ce3+:Y2SiO5 at 2 K. The narrowest spectral holes appear for small applied magnetic fields and are 6±4 MHz wide (FWHM). This puts an upper bound on the homogeneous linewidth of the transition to 3±2 MHz, which is close to lifetime limited. The spin level relaxation time is measured to 72±21 ms with a magnetic field of 10 mT. A slow permanent hole burning mechanism is observed. If the excitation frequency is not changed the fluorescence intensity is reduced by more than 50% after a couple of minutes of continuous excitation. The spectral hole created by the permanent hole burning has a width in the tens of MHz range, which indicates that a trapping mechanism occurs via the 5d state.
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| 50. |
- Kern, Ralph, et al.
(författare)
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Coulomb Excitation of Proton-rich N = 80 Isotones at HIE-ISOLDE
- 2020
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1555:1
-
Tidskriftsartikel (refereegranskat)abstract
- A projectile Coulomb-excitation experiment was performed at the radioactive ion beam facility HIE-ISOLDE at CERN. The radioactive 140Nd and 142Sm ions were post accelerated to the energy of 4.62 MeV/A and impinged on a 1.45 mg/cm2-thin 208Pb target. The γ rays depopulating the Coulomb-excited states were recorded by the HPGe-array MINIBALL. The scattered charged particles were detected by a double-sided silicon strip detector in forward direction. Experimental γ-ray intensities were used for the determination of electromagnetic transition matrix elements. Preliminary results for the reduced transition strength of the B(M1 23+ to 21+)=0.35(19) μN2 of 140Nd and a first estimation for 142Sm have been deduced using the Coulomb-excitation calculation software GOSIA. The 23+ states of 140Nd and 142Sm show indications of being the main fragment of the proton-neutron mixed-symmetry 21, ms+ state.
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