Yu. D. Zavartsev

Continuous wave diode pumped intracavity doubled Nd: GdVO4 laser with 840 mW output power at 456 nm

Abstract We present a diode pumped Nd:GdVO4 ground-state laser at 912 nm with a maximum cw output power of nearly 2.1 W at 16.7 W pump power. The slope efficiency was 16% with respect to the incident power. Also intracavity second harmonic generation (SHG) with an LBO crystal into the blue spectral range at 456 nm was achieved with a maximum output power of 840 mW. In addition the spectral data of Nd:GdVO4 are presented and compared with those of Nd:YVO4 and Nd:YAG.

Czochralski growth and characterization of (Lu1 − xGdx)2SiO5 single crystals for scintillators

Abstract The Czochralski growth of high quality single crystals of cerium doped mixed oxyorthosilicates, (Lu1 − xGdx)2SiO5, where x = 0, 0.2, 0.5, 0.9, and 1.0 is reported. Their growth conditions, defects, structural stability, physical and scintillation properties versus composition have been evaluated. The mixed crystals can be an alternative to both LSO and GSO scintillators.

Performance of a Tm3+:GdVO4 microchip laser at 1.9 μm

Abstract GdVO 4 as a host for thulium has several advantages for diode pumping. The absorption cross section of thulium in GdVO 4 is considerably stronger and broader than in YAG and YLF, and the spectrum is shifted closer to the emission wavelength of commercially available AlGaAs laser diodes. In our paper we compare the 2 μm transition in Tm:GdVO 4 with the one in Tm:Ho:GdVO 4 . The population dynamics in the two crystals is discussed. Furthermore, we report on the optimisation of a Tm 3+ (6.9 at.%):GdVO 4 microchip laser with respect to high efficiency. CW lasing is established at room temperature in a wavelength range around 1.95 μm. The lowest threshold achieved is 310 mW and the highest slope efficiency is 21%.

Spectroscopic properties and lasing of Nd:Gd0.5La0.5VO4 crystals

Abstract We report on the synthesis and spectroscopic characterization of new neodymium doped disordered laser crystals of Gd0.5La0.5VO4 for diode laser pumping. The neodymium 4 F 3 2 lifetime is 100 μs and the crystals have a broad (2 nm) absorption band at 808 nm and a high emission cross section (3 × 10−19 cm2) at 1.06 μm. Under diode pumping 550 mW of output power at 1.06 μm has been achieved at a slope efficiency of 41%.

Laser operation and spectroscopy of Tm: Ho: GdVO4

Abstract Laser operation on the Ho 5 I 7 - 5 I 8 2 μm transition in Tm: Ho: GdVO 4 is described, to our knowledge for the first time. This material has very strong and broad absorption bands, α = 19.1 cm -1 at 797 nm with a fwhm of 7 nm, which is very desirable for diode pumping. The fluorescence spectrum is continuous from 1.9 to 2.07 μm with two closely spaced peaks at 2.04 and 2.05 μm. A 0.7 mm long Tm: Ho: GdVO 4 sample was pumped by a titanium sapphire laser using the active mirror geometry to achieve 90% pump absorption efficiency. Room temperature lasing was achieved at 2.049 μm.

Raman spectroscopic study of structural disordering in YVO4, GdVO4, and CaWO4 crystals

The Raman spectra of single-crystal YVO4, GdVO4, and ZrSiO4 with a zircon structure, as well as CaWO4 and BaWO4 with a scheelite structure, are studied in detail over a wide temperature range 14–800 K. An inhomogeneous splitting of the A1g(ν2) vibrational lines in the Raman spectra of YVO4 and GdVO4 and the Ag(ν1) vibrational lines in the spectrum of CaWO4 is detected. It is shown that the profiles of these lines can be decomposed into two components, whose integrated intensities are redistributed with temperature and also depend on the matrix kind in which they are detected. The phenomenon observed is associated with the thermally activated processes of disorientation of the tetrahedral anions in the zircon and scheelite structures.

New lasers based on c-cut vanadat crystals

Spectroscopic and lasing properties of c-cut Nd-doped Nd:Gd0.7Y0.3VO4, Nd:YVO4, and Nd:GdVO4 crystals were investigated. Spectral tuning from 1062 to 1067 nm was demonstrated. CW, Q-switching and mode-locking regimes for two-color laser operations were realized. A novel THz source based on Q-switch two-color diode-pumped solid state c-cut Nd:GdVO4 laser with Filter Lio as selective element and the GaSe nonlinear optical crystals as convertor was demonstrated. Terahertz radiation with wavelength 436 mm (0.56 THz) was detected. One picosecond laser pulses in mode-locking diode pumped c-cut vanadat lasers with a Kerr-lens and PbS-doped glasses as saturable absorbers are observed.

Structural transformations in LiGd9(SiO4)6O2 and Ca2Gd8(SiO4)6O2 crystals containing isolated [SiO4] complexes: Raman spectroscopic study

The vibrational spectra of single crystals of the LiGd9(SiO4)6O2 and Ca2Gd8(SiO4)6O2 oxyapatites have been studied using Raman spectroscopy at room and high temperatures. The spectra of internal and external vibrations in these structures have been resolved. The structural transformation of the LiGd9(SiO4)6O2 and Ca2Gd8(SiO4)6O2 oxyapatites in the processes of melting and crystallization, as well as during rapid quenching of the melt, has been investigated. It has been found that the melting of the LiGd9(SiO4)6O2 compound has an incongruent character and that new metastable disordered phases are formed during rapid quenching of the Ca2Gd8(SiO4)6O2 melt.

Surface tension and electrocapillary phenomena of yttrium scandium gallium garnet melts

Abstract The surface tension σ of the yttrium scandium gallium garnet melt (the melting point is 2150 K) was measured by the method of tearing off the iridium probe from the melt surface. The temperature dependence of σ was determined in a nitrogen atmosphere at 0.6 atm in the range of melt temperatures of 2156 to 2218 K. Experimental data are presented as σ=1456+0.24 ( T -2156) dyn/cm. The measurements at different partial pressures of N 2 and O 2 were carried out at a melt temperature of 2156 K. Furthermore, the influence of electric field on the surface tension of YSGG melt was investigated. Experimental results are presented as dependence of σ versus current density.

New radiation resistant scintillator LFS-3 for electromagnetic calorimeters

The results of the study of optical and luminescence characteristics of new LFS-3 heavy scintillation crystals are presented. Advantages of these crystals in comparison with conventional scintillators are discussed. The radiation resistance of LFS-3 scintillation crystals is studied using an intense 60Co radioactive source and a proton beam with an energy of 155 MeV. No changes in the optical transmission of LFS-3 crystals after their irradiation with a dose of 23 Mrad are detected.