Institute of Laser Physics

Hamburg, Germany

Institute of Laser Physics

Hamburg, Germany
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Semenov S.,Keele University | Kellam J.,Carolinas Medical Center | Sizov Y.,TRINITI | Nazarov A.,INTEGRIT | And 5 more authors.
Physics in Medicine and Biology | Year: 2011

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.


Koopmann P.,Institute of Laser Physics | Peters R.,Institute of Laser Physics | Petermann K.,Institute of Laser Physics | Huber G.,Institute of Laser Physics
Applied Physics B: Lasers and Optics | Year: 2011

We report on the crystal growth, spectroscopic investigations, and laser experiments of thulium-doped Lu2O3. Crystals with dopant concentrations between 0.2 at.% and 10 at.% were grown by the Nacken-Kyropoulos and the Heat-Exchanger Method. Absorption and emission spectra are presented, as well as the lifetimes of the energy levels involved in the laser process. The laser experiments were carried out using a Ti:sapphire laser emitting at 796 nm as the pump source, achieving a maximum slope efficiency of 68% with respect to the absorbed pump power and a maximum output power of 1.5 W. A continuous tuning range from 1900 nm to 2110 nm was obtained. © 2011 Springer-Verlag.


Frolov S.A.,Institute of Laser Physics | Trunov V.I.,Institute of Laser Physics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

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.


Calmano T.,Institute of Laser Physics | Siebenmorgen J.,Institute of Laser Physics | Hellmig O.,Institute of Laser Physics | Petermann K.,Institute of Laser Physics | Huber G.,Institute of Laser Physics
Applied Physics B: Lasers and Optics | Year: 2010

Tracks of modified material were written with femtosecond-laser pulses in neodymium-doped YAG crystals. Due to a stress-induced change of the refractive index, waveguiding beside the tracks and between two adjacent tracks with a distance of approximately 25 μ m was observed. Loss measurements resulted in guiding losses of about 1.6 dB/cm for the double track waveguide. Spectro-scopic investigations of the 4F 3/2 → 4F 11/2 transmission lines of the neodymium ions, which are close to the modified region, revealed a small stress-induced red shift of the lines. Laser oscillation of single-track waveguides and doubletrack waveguides was demonstrated with Ti:Sapphire laser pumping at a wavelength of 808 nm. Best laser performance with about 1.3 W output power at 2.25 W launched pump power was achieved using a double-track waveguide with a separation of 27 μ m at an outcoupling transmission of 95%. © 2010 Springer-Verlag.


Calmano T.,Institute of Laser Physics | Paschke A.-G.,Institute of Laser Physics | Siebenmorgen J.,Institute of Laser Physics | Fredrich-Thornton S.T.,Institute of Laser Physics | And 3 more authors.
Applied Physics B: Lasers and Optics | Year: 2011

Using the direct femtosecond-laser writing technique tracks of modified material were written in an Yb(15%):YAG ceramic. Due to a stress-induced change of the refractive index between two parallel tracks waveguiding was achieved in channels between the tracks. Laser oscillation of these channel waveguides at a wavelength of 1030 nm was demonstrated with a maximum output power of 0.7 W. The investigation of two different outcoupling transmissions of 99% and 91% revealed that for the higher output coupling the slope efficiency is 35%, which is much lower in comparison to the case of lower output coupling with a slope efficiency of 65%. This effect may be explained by inversion dependent loss mechanisms. © Springer-Verlag 2011.


Reichert F.,Institute of Laser Physics | Fechner M.,Institute of Laser Physics | Koopmann P.,Institute of Laser Physics | Brandt C.,Institute of Laser Physics | And 2 more authors.
Applied Physics B: Lasers and Optics | Year: 2012

We report on crystal growth, spectroscopic investigations, crystal field tuning, and laser experiments of neodymium doped mixed sesquioxides (Lu 1-xSc x) 2O 3. Crystals were grown by the Nacken-Kyropoulos and the Heat-Exchanger method. Emission spectra for several mixing ratios are presented. Cw laser experiments were carried out with a 0.35 at.%-doped Nd:Lu 1.82Sc 0.18O 3 crystal by using a Ti:sapphire laser as pump source, achieving a maximum slope efficiency of 47% with respect to the absorbed pump power and a maximum output power of 356mW at a wavelength of 952.7 nm. To the best of our knowledge, this represents the first continous wave (cw) laser operation of a Nd-doped mixed sesquioxide. © Springer-Verlag 2012.


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 | Year: 2014

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.


Vatnik S.M.,Institute of Laser Physics | Vedin I.A.,Institute of Laser Physics | Pavlyuk A.A.,RAS Institute of Chemistry
Laser Physics Letters | Year: 2012

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.


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 | Year: 2012

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.


Vatnik S.,Institute of Laser Physics | Vedin I.,Institute of Laser Physics | Pujol M.C.,Rovira i Virgili University | Mateos X.,Rovira i Virgili University | And 5 more authors.
Laser Physics Letters | Year: 2010

Continuous-wave (CW) Tm-laser operation is achieved for the first time using the thin disk laser concept and an epitaxial active element based on the monoclinic KLu(WO4)2 crystal with 15 at.% thulium doping of the overgrown layer, which is only 80 μm thick. A single double pass of the pump radiation from the diode-laser ensures efficient pumping due to the large absorption of the active layer. For output coupling between 0.4% and 2.8%, the slope efficiency in the CW regime is in the 7-11% range and the laser threshold amounts to 1.5-2.5 W of absorbed pump power. The laser emission spectra are centered at ~ 1850, 1915, and 1940 nm for output couplers of 2.8%, 1.6%, and 0.4% transmission, respectively. In all cases the emission spectra are "structured", consisting of a number (typically 5-10) of narrow emission lines spread irregularly over 15-30 nm. © 2010 by Astro Ltd.

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