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    Efficient continuous-wave operation of a diode-pumped Nd:YVO4 laser at 1342 nm
    (Elsevier Science Bv, 1999) Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851
    The experimental study described in this paper investigates the continuous-wave power performance of an efficient diode-pumped Nd:YVO4 laser at 1342 nm by employing four different end pumping configurations. When pumped by a high-power fiber-coupled diode array at 806 nm, the compact resonator consisting of a 9.25-mm long Nd:YVO4 crystal and a 3.6% transmitting output coupler produced as high as 3550 mW of output power. The absorbed power slope efficiency was measured to be 28.1%. By using the experimentally measured threshold data, the stimulated emission cross-section of the gain medium was determined to be 13 X 10(-19) cm(2) at 1342 nm. Above absorbed pump powers of 11 W, strong thermal loading caused saturation of the output power and the focal length of the induced thermal lens was measured as a function of the pump power. Results further showed that the laser output was insensitive to variations in the crystal boundary temperature between 20 degrees C and 40 degrees C.
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    Experimental determination of fractional thermal loading in an operating diode-pumped Nd: YVO4 minilaser at 1064 nm
    (Optical Soc Amer, 1999) Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851
    A practical in, situ method is described and used for determination of the fractional thermal-loading parameter eta(h) in an operating diode-pumped Nd:YVO4 minilaser at 1064 nm. Readily applicable to the thermal characterization of other solid-state media, the method is based on the fact that thermally induced lensing will cause the laser oscillation to be quenched at a critical pump power whose magnitude depends on the cavity configuration, thermo-optical properties of the gain medium, and, in particular, on the value of eta(h). In the experiments described here, a 0.5-mm-long coated Nd:YVO4 crystal with 3-at. % Nd concentration was used to construct the diode-pumped laser with a flat highly reflecting end mirror and an intracavity lens. For the method to be effective, the resonator was set up close to the edge of the stability range. Above the oscillation threshold, the pump power at which lasing was quenched because of the onset of the thermally induced resonator instability was measured as a function of the intracavity lens position. A numerical model that accounted for absorption saturation and pump-induced thermal lensing was then used to analyze the experimentally measured data with eta(h) as an adjustable parameter. The average best-fit value of eta(h) was determined to be 0.40 with an estimated statistical variation of 8%.
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    Alternative polynomial and holomorphic Dunford-Pettis properties
    (Scientific and Technical research Council of Turkey - TUBITAK/Türkiye Bilimsel ve Teknik Araştırma Kurumu, 1999) Department of Mathematics; Freedman, Walden; Faculty Member; Department of Mathematics; College of Sciences; N/A
    Alternatives to the Polynomial Dunford-Pettis property and the Holomorphic Dunford-Pettis property, called the PDP1 and HDP1 properties, respectively, are introduced. These are shown to be equivalent to the DP1 property, an alternative Dunford-Pettis property previously introduced by the author, thus mirroring the equivalence of the three original properties. © TÜBİTAK.