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Ricaud S.,University Paris - Sud | Ricaud S.,Amplitude Systemes | Jaffres A.,CNRS Laboratory of Condensed Matter Chemistry, Paris | Loiseau P.,CNRS Laboratory of Condensed Matter Chemistry, Paris | And 10 more authors.
Optics Letters | Year: 2011

We present the first demonstration of a Yb:CALGO thin-disk laser. In a slightly multimode configuration, we obtained up to 30 W of average power at a slope efficiency of 40% and an optical-to-optical efficiency of 32%. With a single-mode cavity, an average power of 25W was achieved. A tuning range from 1018 to 1052nm could be demonstrated by inserting a prism into the cavity. In the Q-switched regime, we obtained 1 mJ of pulse energy at a repetition rate of 100 Hz. © 2011 Optical Society of America. Source


Tyunina M.,University of Oulu | Tyunina M.,ASCR Institute of Physics Prague | Dejneka A.,ASCR Institute of Physics Prague | Rytz D.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | And 4 more authors.
Journal of Physics Condensed Matter | Year: 2014

Sodium niobate (NaNbO3, or NNO) is known to be antiferroelectric at temperatures between 45 and 753 K. Here we show experimentally the presence of the ferroelectric phase at temperatures between 100 and 830 K in the NNO crystals obtained by top-seeded solution growth. The ferroelectric phase and new phase transitions are evidenced using a combination of thermo-optical studies by variable angle spectroscopic ellipsometry, Raman spectroscopy analysis, and photoelectron emission microscopy. The possibility for strain-induced ferroelectricity in NNO is suggested. © 2014 IOP Publishing Ltd. Source


Schwung S.,Munster University of Applied Sciences | Enseling D.,Munster University of Applied Sciences | Wesemann V.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | Rytz D.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | And 6 more authors.
Journal of Luminescence | Year: 2014

High-quality single crystals of partially europium-substituted KYW2O8 (KYW) were grown by the top-seeded solution growth technique. The structures of four crystals with different europium content were refined on the basis of single crystal X-ray diffractometer data. The trivalent character of europium in these crystals was manifested through 151Eu Mössbauer spectra and magnetic susceptibility measurements. Moreover, reflection and photoluminescence spectra were recorded and from these spectra the quantum efficiency, lumen equivalent, and CIE1931 color point were calculated. It turned out that Eu3+ doped KYW is an efficient photoluminescent material at room temperature, while the thermal quenching temperature T1/2 is at about 633 K (360 °C), thus making the material a potential radiation converter for light emitting diodes. © 2014 Published by Elsevier B.V. Source


Schwung S.,Munster University of Applied Sciences | Rytz D.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | Gross A.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | Rodewald U.C.,University of Munster | And 6 more authors.
Optical Materials | Year: 2014

Centimeter size LiEu(MoO4)2 bulk single crystals have been grown by top-seeded solution growth using Li2MoO4 as a flux. The resulting crystals exhibited different coloration shades from dark to bright violet. Small single crystal fragments were studied by X-ray diffraction: CaWO4 type, space group I41/a, a = 519.74(4), c = 1132.56(11) pm, wR2 = 0.0143, 270 F2 values at 300 K and a = 518.70(4), c = 1130.25(11) pm, wR2 = 0.0197, 268 F2 values at 90 K. The Li+ and Eu3+ cations statistically occupy the 4b site. Down to 90 K, the single crystal X-ray data give no hint for cation ordering. Some of the grown crystals show dark violet color. This is due to defects in the oxygen substructure accompanied by partial reduction of Mo6+ (d 0) to Mo5+ (d1) which was detected by electron spin resonance. 151Eu Mössbauer spectra of the bright and also of the dark violet LiEuMo2O8 samples show the presence of trivalent europium solely. Temperature dependent magnetic susceptibility data exhibit weak van Vleck type paramagnetism as a consequence of trivalent europium ([Xe]4f6). The dark violet samples show slightly higher susceptibility due to the contribution of Mo5+. These data point to a formula LiEuMo2O8-x for the violet samples. 7Li solid state NMR spectra underline the single lithium sites in both samples. Both colored crystals show identical emission spectra, which indicate the same chemical surrounding of the trivalent europium ions. However, excitation spectra and thermal quenching and decay curves points to a higher defect density in the violet sample. © 2013 Elsevier B.V. All rights reserved. Source


Weichelt B.,University of Stuttgart | Rumpel M.,University of Stuttgart | Voss A.,University of Stuttgart | Gross A.,Forschungsinstitut fur Mineralische und Metallische Werkstoffe Edelsteine Edelmetalle GmbH | And 4 more authors.
Optics Express | Year: 2013

The first demonstration of an Yb:YAl3(BO3)4 thin-disk laser is reported. An output power of 109 W with an optical efficiency of 50.2% was achieved in multimode CW-operation which is to the best of our knowledge a significant record performance compared to previous reports on CW-lasers with this material. At a lower power level of 19.3 W the material proved its suitability for efficient operation with an optical efficiency of 60.4%. In fundamental-mode operation the extracted output power was 10.4 W with an optical efficiency of 44.5% and a beam propagation factor M2 = 1.39. The broad emission bandwidth of the material was confirmed by measuring a continuous wavelength tuning range from 1001 to 1053 nm with a maximum output power of 36 W at 1040 nm. ©2013 Optical Society of America. Source

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