| 1. |
- Andersson-Engels, Stefan, et al.
(author)
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Deep-tissue optical imaging and photoactivation activities at biophotonics@tyndall
- 2016
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In: Frontiers in Optics, FiO 2016. - 2162-2701. - 9781943580194
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Conference paper (peer-reviewed)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.
(author)
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Characterization and modeling of acousto-optic signal strengths in highly scattering media
- 2019
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In: Biomedical Optics Express. - 2156-7085. ; 10:11, s. 5565-5584
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Journal article (peer-reviewed)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. |
- Gunther, Jacqueline, et al.
(author)
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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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In: Journal of Biomedical Optics. - 1083-3668. ; 23:7
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Journal article (peer-reviewed)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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| 4. |
- Gunther, Jacqueline, et al.
(author)
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Theoretical study of combined acousto-optical tomography and slow light filters
- 2018
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In: Optical Tomography and Spectroscopy, OTS 2018. - 9781557528209 ; Part F90-OTS 2018
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Conference paper (peer-reviewed)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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| 5. |
- Walther, Andreas, et al.
(author)
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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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In: Biomedical Optics Express. - 2156-7085. ; 8:10, s. 4523-4536
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Journal article (peer-reviewed)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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| 6. |
- Karlsson, Jenny, et al.
(author)
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A confocal optical microscope for detection of single impurities in a bulk crystal at cryogenic temperatures
- 2016
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 87:3
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Journal article (peer-reviewed)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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| 7. |
- Karlsson, Jenny, et al.
(author)
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High-resolution transient and permanent spectral hole burning in Ce3+ : Y2SiO5 at liquid helium temperatures
- 2016
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In: Physical Review B. - 1098-0121. ; 93:22
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Journal article (peer-reviewed)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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| 8. |
- Kern, Ralph, et al.
(author)
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Search for Isovector Valence-Shell Excitations in 140Nd and 142Sm via Coulomb excitation reactions of radioactive ion beams
- 2018
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In: International Conference on Nuclear Structure and Related Topics (NSRT18). - : EDP Sciences. - 2101-6275. ; 194
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Conference paper (peer-reviewed)abstract
- Projectile Coulomb excitation experiments were performed at HIE-ISOLDE at CERN with the radioactive ion beams of 140Nd and 142Sm. Ions with an energy of 4:62 MeV/A were impinging on a 1.45 mg/cm2 thick 208Pb target. The γ-rays depopulating the Coulomb-excited states were recorded by the HPGe-array MINIBALL and scattered particles were detected by a double-sided silicon strip detector. Experimental intensities were used for the determination of electromagnetic transition matrix elements. A preliminary result of the B(M1; 2+ 3 → 2+ 1) of 140Nd and an upper limit for the case of 142Sm are revealing the main fragments of the proton-neutron mixed-symmetry 2+ 1;ms states.
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| 9. |
- Kinos, Adam, et al.
(author)
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Development and characterization of high suppression and high étendue narrowband spectral filters
- 2016
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In: Applied Optics. - 1559-128X. ; 55:36, s. 10442-10448
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Journal article (peer-reviewed)abstract
- The present work addresses critical issues in constructing high suppression, narrowband spectral filters in rare-earth-ion-doped crystals, mainly targeting the application of ultrasound optical tomography but is also applicable for areas such as quantum memories, self-filtering of laser frequencies, and other applications relying on high absorption in rare-earth-ion-doped crystals. The polarization of light transmitted through a highly absorbing crystal is experimentally analyzed. Additionally, an existing wave propagation method is used to simulate beam propagation through a spectral hole to study the high étendue requirements of ultrasound optical tomography.
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| 10. |
- Li, Qian, et al.
(author)
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Slow-light-based optical frequency shifter
- 2016
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 93:4
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Journal article (peer-reviewed)abstract
- We demonstrate experimentally and theoretically a controllable way of shifting the frequency of an optical pulse by using a combination of spectral hole burning, slow light effect, and linear Stark effect in a rare-earth-ion-doped crystal. We claim that the solid angle of acceptance of a frequency shift structure can be close to 2π, which means that the frequency shifter could work not only for optical pulses propagating in a specific spatial mode but also for randomly scattered light. As the frequency shift is controlled solely by an external electric field, it works also for weak coherent light fields and can be used, for example, as a frequency shifter for quantum memory devices in quantum communication.
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