Jinghe Liu

Spectral properties of Tm,Ho:LiYF4 laser crystal

Abstract The LiYF 4 single crystal codoped with thulium and holmium ions was successfully grown by the Cz method. The optimal technical parameters obtained were as follows: the pulling rate was 0.16 mm/h; the rotation speed was 3 rpm; the cooling rate was 15 °C/h. The result of XRD curve showed that as-grown Tm,Ho:LiYF 4 laser crystal belonged to the monoclinic system with scheelite-type structure and space group I41/a. The cell parameters calculated were: a =0.52160 nm, c =1.09841 nm and Z =4. Absorption and fluorescence spectra of Tm,Ho:LiYF 4 laser crystal at room temperature were measured and analysed. The absorption cross section, FWHM and absorption coefficient at 779.3 nm calculated were 7.44×10 −21 cm 2 , 8.7 nm and 2.23 cm −1 , respectively. An intensive fluorescence emission peak appeared near 2045 nm. The emission cross section and fluorescence lifetime were 0.87×10 −20 cm 2 and 10.8 ms, respectively. The ratio of Tm-Ho transfer to its back-transfer process was 10.6.

Crystal Growth and Spectral Properties of Yb3+:KY(WO4)2

Abstract Laser crystal Yb:KYW was grown by the Kyropoulos method. A grown crystal was identified as β-Yb:KYW by XRD. By TG-DTA the melting point and transition point of the crystal are 1045 and 1010 °C, respectively. Infrared spectrum and Raman spectrum were measured, and the vibrational frequencies of infrared and Raman active modes for Yb:KYW crystal were assigned. Absorption spectrum of Yb:KYW shows that there are two intensive absorption peaks at 940 and 980 nm, respectively, and the absorption cross section is 1.34 × 10−19 cm2 at chief peak of 980 nm. There exist three intensive emission peaks in Yb:KYW at 990, 1010 and 1030 nm, respectively, and the emission line width of the chief peak 1030 nm runs up to 16 nm. It was calculated that the peak emission cross section is 3.1 × 10−20 cm2 at 1030 nm.

Nanostructured Yb:GGG polycrystalline powders via gel combustion method

Abstract Gadolinium gallium garnet (GGG) nanopowders doped with ytterbium ions (Yb:GGG) were synthesized with citric acid as a fuel via gel combustion method. The optimized conditions for preparing Yb 3+ :Gd 3 Ga 5 O 12 nanopowders were discussed. The heat behavior, structure and morphology of powders were analyzed with thermal analysis (TG-DTA), X-ray diffraction (XRD), infrared spectra (IR) and transmission electron microscope (TEM). TG-DTA analysis revealed that the weight loss of the precursor occured below 800 °C and its crystallization temperature was 830.6 °C. XRD and IR analysis showed that the precursor converted directly into pure GGG at a relatively lower temperature (900 °C) without any other intermediate phase. The lattice constant was 1.2377 calculated by extrapolation method. TEM results indicated that the spherical powders showed good dispersity and had a relatively narrow size distribution with average particle size of approximately 40–50 nm, which was favorable for good sinterability of Yb:GGG laser ceramic.

Growth, structure and spectral characteristics of KEr0.1Yb0.9(WO4)2 laser crystal

Abstract The 10 at.% Er 3+ -doped KYb(WO 4 ) 2 (KEr 0.1 Yb 0.9 (WO 4 ) 2 ) laser crystal with dimensions up to 25 mm × 15 mm × 10 mm was grown by the Kyropoulos method. The crystal structure was identified as β-KEr 0.1 Yb 0.9 (WO 4 ) 2 by XRD analysis. Through TG-DTA curves, the melting point and transition point of the crystal were determined to be 1058 and 1031 °C, respectively. Infrared spectrum and Raman spectrum were measured, and the vibration frequencies of infrared and Raman active modes for the crystal were assigned. The absorption cross section is 3.1 × 10 −20 cm 2 at chief peak of 981 nm with the absorption line width of 26 nm. Based on the Judd-Ofelt theory, the intensity parameters Ω λ ( λ =2,4,6) calculated were: Ω 2 =16.34 × 10 −20 cm 2 , Ω 4 =4.18 × 10 −20 cm 2 , and Ω 6 =1.26 × 10 −20 cm 2 . There was a strong emission peak near 1533 nm and the emission line width at the main peak at 1533 nm run up to 55 nm with the emission cross section of 3.47 × 10 −20 cm 2 . These optical parameters indicated the potential of this crystal used as an excellent laser material for 1540 nm nearby human-eye safe.

Growth and spectral properties of Tm:BaY2F8 crystals with different Tm3+ concentration

Tm3+:BaY2F8 (Tm:BYF) laser crystals with different doping concentrations were successfully grown by Czochralski method. The optimal growth parameters obtained are as follows: the pulling rate is 0.5 mm/h; the rotation speed is 5 rpm; the cooling rate is 10°C/h. Phase composition, absorption spectra, and fluorescence properties of crystals were studied by XRD and spectral methods. XRD analysis indicates that the crystal belongs to monoclinic system with the C2/m space group. The lattice parameters were calculated and the anisotropy of the crystals was studied, confirming that the a axis is the best growth direction. The absorption peaks around 790 nm became larger with increase of Tm3+ concentration. The cross section of 15% Tm:BYF crystal around 791 nm is 9.47 × 10–21 cm2. The 10% Tm:BYF crystal has the strongest emission peak around 1879.6 nm with the FWHM of 79 nm and the emission cross-section of 2.13 × 10–21 cm2, which is favorable for the 1.88 μm laser output.

Growth and properties of neodymium-doped terbium aluminum garnet crystal

Neodymium doped terbium aluminum garnet (Nd:TAG) crystal with dimensions of Ø30 × 90 mm was grown by the Czochralski method. The Nd:TAG crystal was characterized by X-ray diffraction, IR spectroscopy, absorption and fluorescence spectra, and laser performance test. The strongest absorption peak is located at 808 nm. There are 3 main fluorescence emission peaks located at 1062, 1108, and 1332 nm, respectively. The prepared 3 at % Nd:TAG crystal was pumped by InGaAs laser diode, the pumping threshold was 360 mW, the highest laser output was 310 mW, the light-light conversion efficiency was 32.3% and the slope efficiency was 51.7%.

Synthesis and characterization of Er:Yb3Al5O12 nanopowder

Er:Yb1Al5O12 (Er:YbAG) nanopowder was prepared by carbonate coprecipitation method. Highpurity Er:YbAG powder was obtained after calcination at as low as 1000°C with an average particle size of 70 nm. The Al–O–Yb phonon vibrations were investigated and the absorption band arisen from interaction between lattice vibration and photon in YbAG is located around 610 cm–1. A strong emission peak of powder was observed at 1.53 µm with 980 nm laser excitation. An energy transfer mechanism between Yb3+ and Er3+ states responsible for the peak emission was proposed. An optimum Er3+ dopant concentration was determined.

Synthesis and characterization of Er:Yb3

Er:Yb1Al5O12 (Er:YbAG) nanopowder was prepared by carbonate coprecipitation method. Highpurity Er:YbAG powder was obtained after calcination at as low as 1000°C with an average particle size of 70 nm. The Al–O–Yb phonon vibrations were investigated and the absorption band arisen from interaction between lattice vibration and photon in YbAG is located around 610 cm–1. A strong emission peak of powder was observed at 1.53 µm with 980 nm laser excitation. An energy transfer mechanism between Yb3+ and Er3+ states responsible for the peak emission was proposed. An optimum Er3+ dopant concentration was determined.

Synthesis and characterization of Er:Yb 3 Al 5 O 12 nanopowder

Er:Yb1Al5O12 (Er:YbAG) nanopowder was prepared by carbonate coprecipitation method. Highpurity Er:YbAG powder was obtained after calcination at as low as 1000°C with an average particle size of 70 nm. The Al–O–Yb phonon vibrations were investigated and the absorption band arisen from interaction between lattice vibration and photon in YbAG is located around 610 cm–1. A strong emission peak of powder was observed at 1.53 µm with 980 nm laser excitation. An energy transfer mechanism between Yb3+ and Er3+ states responsible for the peak emission was proposed. An optimum Er3+ dopant concentration was determined.

Study on the Growth, Defects, and Optical Properties of Tm:YAP Crystal

Tm:YAP crystal was grown by the Czochralski method. Color center absorption phenomenon is significantly weakened in the ultraviolet and visible region. Dominated forced convection or increased crystal diameter may reduce the crystal-like scattering dispersion. The average value of absorption coefficient and cross-section are calculated to be 2.09 cm−1 and 6.03 × 10−21 cm2, respectively. The described techniques may be useful for the further improvement of the quality of Tm:YAP crystals.