A. I. Zagumennyi

Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4

We have carried out a detailed spectroscopic characterization of Nd: GdVO4, a new laser crystal with high effective absorption and emission cross sections. The accidental degeneracy of the upper4F3/2 laser level decreases the number of emission lines and creates -together with the anisotropic crystal field - high emission cross sections (7.6 × 10−19 cm2 at 1.06 µm and 300 K). In addition, the lines are strongly homogeneously broadened (1.6 nm for the 808.4 nm diode-laser pump transition). The temperature dependences of lifetime, linewidths, and cross sections have been determined. Slope efficiencies up to 57% with respect to the absorbed diode-laser pump power and output powers up to 0.8 W have been achieved at 1.06 µm from a 2 mm long crystal. Intracavity second-harmonic generation, using a KTP crystal, is demonstrated.

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%.

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.

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.

GaS x Se 1−x compounds for nonlinear optics

We measure the nonlinearity and transparency of mixed GaS x Se 1−x crystals and show that GaS 0.4 Se 0.6 is a promising nonlinear material for mid-IR (≫5 µm) OPO operation without twophoton absorption for a pump wavelength of 1064 nm.

Tunable efficient continuous-wave room-temperature Tm3+:GdVO4 laser

We report room-temperature continuous-wave laser operation, tunable over 1.86 to 1.99 μm range with up to 55 % slope efficiency at the 3F4 ->3H6 transition in Tm3+:GdVO4 laser. Threshold pump power as low as 86 mW was measured.

GdVO4 crystals with Nd3+, Tm3+, Ho3+, and Er3+ ions for diode-pumped microchip laser

The Nd:GdVO4, Ho:Tm:GdVO4, Tm:GdVO4, Er:GdVO4, Yb:GdVO4 crystals were grown by Czochralski technique. Distribution coefficients of Yb3+, Tm3+, Er3+, Nd3+ ions depend linearly on average radius of a dodecahedral ion. Refractive indices are measured with accuracy within 5 by 10-5 in a range 400 - 1100 nm. Refractive indices depend on the size of the average dodecahedral radius. The thermal conductivity of the doped crystals in the 50 - 300 K temperature range is measured. The thermal conductivity in the <001> crystal direction at a temperature of 300 K is 12.3 W/m by K it is more than thermal conductivity of well-known Nd:YAG laser crystal. As a result of analysis it is shown that vanadate crystals have essential advantages for diode pump lasers in comparison with conventional YAG and YVO4 hosts: large stimulated emission cross section at lasing wavelength; wide absorption band at pump wavelength; low dependency on a pump wavelength and a temperature control of a diode laser; low lasing threshold. For compact design lasers were made crystals with thickness from 2 mm up to 150 micrometers. Microchip laser (monolithic laser) consists of flat-flat cavities formed by a short length of crystal with dielectric cavity mirrors deposited directly on the surfaces.