Ludmila I. Ivleva

Luminescence peculiarities and optical properties of MgMoO4 and MgMoO4:Yb crystals

Magnesium molybdate is considered as a promising material for cryogenic scintillation bolometers. The luminescence properties of MgMoO4 have been investigated on single crystals grown from melts of stoichiometric and nonstoichiometric compositions and on crystals doped with Yb3+ ions. Their optical properties are interpreted taking into account the anisotropy of the MgMoO4 crystal structure.

Laser performance of Yb:GdCa4O(BO3)3 compared to Yb:KGd(WO4)2 under diode-bar pumping

A study of Yb:GdCOB under diode-bar pumping has been performed and the results are compared, experimentally and theoretically, with Yb:KGW in the same cavity. An output power of 7.3 W and a slope efficiency of 57.4% were obtained. Self-frequency-doubling experiments are also discussed.

Lasing properties of new Nd3+-doped tungstate, molybdate, and fluoride materials under selective optical pumping

The purpose of this work was to determine the relative efficiencies of new Nd3+-doped laser active/Raman - tungstate, molybdate, and fluoride - materials (SrWO4, PbWO4, BaWO4, SrMoO4, PbMoO4, SrF2, and LaF3) under selective longitudinal optical pumping by the alexandrite (~750nm), or diode (~800nm) laser. Crystals with various length, orientations and active ions concentrations were tested. To optimize the output of the tested lasers a set of input dichroic and output dielectric mirrors with different reflectivities were used. For realized lasers operating at pulsed free-running regime, threshold energy, slope efficiency, emission wavelength, and radiation polarization were determined. For each crystal, fluorescence lifetime and absorption coefficient under given pumping were established. The slope efficiency in case of Nd3+:PbMoO4 laser at wavelength 1054nm was measured to be 54.3% with total efficiency of 46% which is the best result obtained for all new tested crystals. For Nd3+ doped SrWO4, PbWO4, and BaWO4 crystals simultaneous laser and self-Raman emission were demonstrated in Q-switched regime. Thus newly proposed laser Raman crystals demonstrate high efficiency for Nd3+ laser oscillations comparable with well known and widely used Nd:KGW crystal. Further improvement in the quality of tungstate and molybdate type crystals should result in further increase in lasing efficiency at 1.06μm wavelength. Self Raman frequency conversion of Nd3+-laser oscillations in these crystals should result in high efficient pulse shortening, high peak power and new wavelengths in 1.2-1.5μm wavelength region.

Growth of barium tungstate crystals

The paper concerns the growth of BaWO4 crystals by Czochralski method and modified Stepanov technique. The influence of different factors, such as type of die, form of crystallization front, melt composition, thermal conditions, on the real structure of the material was investigated. The origin of the defects in Czochralski-grown and bulk-profiled barium tungstate is discussed. It is shown that the striation-free bulk-profiled crystals of high optical quality can be produced by new developed technique. Comparison of the crystallization conditions for Czochralski method and Stepanov technique is carried out.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Picosecond stimulated Raman scattering in new crystals Nd:SrWO 4 and SrMoO 4

New Nd:SrWO4 and SrMoO4 crystals (45 mm and 33 mm of legnth, respectively) were investigated as Raman frequency converters of 50 picosecond Nd:YAG pulses and compared with already previously measured BaWO4 and KGd(WO4)2(KGW) tungstate crystals (33 mm and 40 mm of length, respectively). A forward SRS action was achieved in both new crystals. During the experiment the threshold energy of stimulated Raman process, generated wavelengths, and conversion efficiencies were measured. Single-pass first Stokes conversion efficiencies reached 25% and 21% for Nd:SrWO4 and SrMoO4 crystals, respectively. These values were compared with the maximal first Stokes efficiencies of previously studied crystals measured in the same experimental setup yielding: BaWO4 (η = 25% and KGW (η = 22%). As concerned the threshold - it was comparable for BaWO4, Nd:SrWO4, and SrMoO4. The SRS effect in KGW crystal started for ~25% higher pump energy. Our study shows that new Nd:SrWO4 and SrMoO4 crystals are other promising materials for picosecond Raman generation.

High-power end-pumped lasers with Yb:GdCa 4 O(BO 3 ) 3 and Yb:KGd(WO 4 ) 2

Summary form only given. The aim of the present work was to compare the performance of Yb:GdCOB and Yb:KGW under end-pumping by a non-fiber-coupled diode-bar.

Diode-pumped 1.54 /spl mu/m Er-Yb:GdCOB lasers

We present the investigation of longitudinally pumped microchip Yb-Er lasers based on new crystalline medium GdCa/sub 4/O(BO/sub 3/)/sub 3/. The main potential advantage of these crystals over Er-Yb glasses is the higher thermal conductivity, which may lead to higher thermal damage threshold. The advantage of GdCa/sub 4/O(BO/sub 3/)/sub 3/ (GdCOB) over YCOB is its lower melting point are discussed.

New crystalline material for 1.5 micrometer lasers: Yb,Er-activated GdCa4O(BO3)3

A new crystalline medium for 1.5 micron Yb-Er lasers is proposed: GdCa4O(BO3)3 (GdCOB). Its melting point allows crystal growth using Pt instead of Ir crucibles. Spectroscopic and laser tests of the new material are described.

Spectral and luminescence characteristics of Nd/sup 3+/ ions in BaWO/sub 4/ Raman crystal

Summary form only given. Barium tungstate crystal was recently developed as a new promising nonlinear material for crystalline nano- and picosecond Raman lasers. Doping this crystal with Nd/sup 3+/ ions could allow its use as a laser active element and a nonlinear Raman medium simultaneously. In this report, we present results on spectroscopic investigations of BaWO/sub 4/ crystal doped with Nd/sup 3+/ impurity ions.

Comparison of stimulated Raman scattering of picosecond pulses in tungsten crystals

Stimulated Raman scattering of picosecond pulses was investigated in KGd(WO4)2, and BaWO4 tungstate crystals. BaWO4 crystal was previously found to be a new very efficient material for pumping with nanosecond pulses. In our experiment, we used the second harmonic output of a mode-locked Nd:YAG laser system, which generated single pulses of 28 ps duration. The length of the crystal was 40 mm for KGW, 23 mm for KYW and 29 mm for BaWO4. The SRS threshold, conversion efficiency, and time dependence of the first Stokes with picosecond resolution were measured. Picosecond Raman gains at a 532 nm wavelength were found to be correspondingly 11.5, 18.7, and 14.4 cm/GW for KGW, KYW, and BaWO4. The Raman shifting up to the third Stokes component was detected, and the first Stokes conversion efficiency reached 30 percent in BaWO4 and 18 percent in KGd(WO4)2. Measurements of a temporal pulse length have shown that the first Stokes pulse was twice shorter than the pump pulse. The new BaWO4 crystal occurs to be an efficient solid state Raman material for a wide variety of pump pulse durations.