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Hamburg, Germany

Semenov S.,Keele University | Kellam J.,Carolinas Medical Center | Sizov Y.,TRINITI | Nazarov A.,INTEGRIT | And 5 more authors.
Physics in Medicine and Biology

Microwave tomography (MWT) is a novel imaging modality which might be applicable for non-invasive assessment of functional and pathological conditions of biological tissues. Imaging of the soft tissue of extremities is one of its potential applications. The feasibility of this technology for such applications was demonstrated earlier. This is the first of two companion papers focused on an application of MWT for imaging of the extremity's soft tissues. The goal of this study is to assess the technical performance of the developed 2D MWT system dedicated for imaging of functional and pathological conditions of the extremity's soft tissues. Specifically, the system's performance was tested by its ability to detect signals associated with physiological activity and soft tissue interventions (circulatory related changes, blood flow reduction and a simulated compartmental syndrome) - the so-called physiological signatures. The developed 2D MWT system dedicated to the imaging of animal extremities demonstrates good technical performance allowing for stable and predictable data acquisition with reasonable agreement between the experimentally measured electromagnetic (EM) field and the simulated EM field within a measurement domain. Using the system, we were able to obtain physiological signatures associated with systolic versus diastolic phases of circulation in an animal extremity, reperfusion versus occlusion phases of the blood supply to the animal's extremity and a compartment syndrome. The imaging results are presented and discussed in the second companion paper. © 2011 Institute of Physics and Engineering in Medicine. Source

Keller J.,Physikalisch - Technische Bundesanstalt | Ignatovich S.,Institute of Laser Physics | Webster S.A.,M Squared Lasers | Mehlstaubler T.E.,Physikalisch - Technische Bundesanstalt
Applied Physics B: Lasers and Optics

We present the design and realization of two reference cavities for ultra-stable lasers addressing narrow transitions in mixed-species ( 115In+ / 172Yb+) Coulomb crystals. With a simple set-up, we achieve a fractional frequency instability close to the thermal noise limit of a 12-cm-long cavity, reaching σ y = 4.7 × 10-16 at 10 s with a linear drift of 53 mHz/s. We discuss the individual instability contributions and show that in a set-up with a lower thermal noise floor and vibration sensitivity, an instability of 1 × 10-16 can be reached. To achieve this, we implement a vibration-insensitive design for a 30-cm-long cavity mounted horizontally and conduct first tests that show a sensitivity of 1.8 × 10-11 ms-2 to vertical accelerations. This is about a factor of 20 less than the value observed for the short cavity. Mechanical tolerances and ways to further reduce the sensitivity are discussed. © 2013 Springer-Verlag Berlin Heidelberg. Source

Vatnik S.M.,Institute of Laser Physics | Vedin I.A.,Institute of Laser Physics | Pavlyuk A.A.,RAS Institute of Chemistry
Laser Physics Letters

We report a high-efficiency room-temperature 5%Tm:KLu(WO4)2 laser relied upon the gain slab-shaped crystal of volume less one and half cubic millimeter. Continuous-wave output power of 10.4W at 1907 nm for 34.2 W of diode pump power has been demonstrated, with optical and slope efficiencies being of 31 and 43%, respectively. Thermal coefficient of optical path was evaluated also, TCOP (E ∥Np)~-2×10-6. © 2012 by Astro, Ltd. Source

Frolov S.A.,Institute of Laser Physics | Trunov V.I.,Institute of Laser Physics
Proceedings of SPIE - The International Society for Optical Engineering

Recent theoretical and experimental studies show that filamentation of femtosecond pulses in middle infrared range in solids can generate intense supercontinuum (SC) with width of a several octaves. The structure and dynamics of the spectrum formation is different from those observed during filamentation of femtosecond pulses in the near infrared range of the spectrum. With numerical modeling we investigate features of infrared (IR) SC generation in a number of solid-state media transparent in a broad infrared range with various bandgaps, including KBr (7.6 eV), ZnS (3.68 eV) and ZnSe (2.71 eV) for different pump wavelengths. SC formation dynamics is analyzed. With comparison of different media, including one with artificial bandgap, we find that lower bandgap decreases SC bandwidth and filamentation length. © 2016 SPIE. Source

Vatnik S.,Institute of Laser Physics | Vedin I.,Institute of Laser Physics | Segura M.,Rovira i Virgili University | Mateos X.,Rovira i Virgili University | And 6 more authors.
Optics Letters

A diode-pumped thin-disk laser based on Tm:KLu(WO4) 2/KLu(WO4)2 epitaxies is realized. The emission is in the 1850-1945 nm spectral range for Tm-doping between 5 and 15 at. %. The maximum slope efficiency of 47% with respect to the absorbed power obtained with 5 at. % Tm:KLu(WO4)2/KLu(WO4)2 corresponds to a maximum output power of ∼6 W in cw operation. © 2012 Optical Society of America. Source

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