Wenlan Gao

Synthesis, growth, and characterization of Nd-doped SrGdGa3O7 crystal

A disordered Nd:SrGdGa3O7 (Nd:SGGM) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd3+ were determined to be P4¯21m and 1.36, respectively. Thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were measured. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. Sellmeier’s equations were fitted by measuring the refractive indices in the range of 253–2325 nm. The polarization absorption and emission spectra were measured at room temperature, and Judd–Ofelt analysis was carried out to calculate the fluorescence branching ratios from the upper F43/2 state and the fluorescence lifetime. The stimulated emission cross section for the F43/2→I411/2 transition was calculated to be 2.00×10−20 cm2. Finally, a diode-pumped laser experiment at 1.06 μm is described. Thermal, optical, and laser properties have show...

Thermal properties of cubic KTa1−xNbxO3 crystals

Cubic potassium tantalite niobate [KTa1−xNbxO3 (KTN)] crystals of large size, good quality, and varying Nb concentration have been grown by the Czochralski method and their thermal properties have been systematically studied. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystals were determined to be: 1536.9 K, 12 068.521 J mol−1, and 7.85 J K−1 mol−1 for KTa0.67Nb0.33O3; and 1520.61 K, 15 352.511 J mol−1, and 10.098 J K−1 mol−1 for KTa0.67Nb0.33O3, respectively. Based on the data, the Jackson factor was calculated to be 0.994f and 1.214f for KTa0.67Nb0.33O3 and KTa0.63Nb0.37O3, respectively. The thermal expansion coefficients over the temperature range of 298.15−773.15 K are: α=4.0268×10−6/K, 6.4428×10−6/K, 6.5853×10−6/K for KTaO3, KTa0.67Nb0.33O3, and KTa0.63Nb0.37O3, respectively. The density follows an almost linear decrease when the temperature increases=from 298.15 to 773.15 K. The measured specific heats at 303.15 K are: 0.375 J g−1 K−1 for KTaO3; 0.421 J g−1 K−1 ...

Ion-implanted optical-stripe waveguides in neodymium-doped calcium barium niobate crystals.

We report on the fabrication and characterization of optical-stripe waveguides in neodymium-doped calcium barium niobate (Nd:CBN) crystals by using He ion implantation assisted with a mask. The guided-mode profiles are successfully modeled through numerical simulations. After annealing at 200 degrees C for 30 min, the waveguide propagation loss could be reduced down to ~3 dB/cm. Room-temperature microluminescence and micro-Raman investigations reveal that the crystal bulk features are well preserved in the active volume of the waveguide, suggesting possible applications as integrated photonic devices.

Nonlinear prism based on the natural ferroelectric domain structure in calcium barium niobate

We show the ability of calcium barium niobate as a nonlinear material to produce conical second harmonic generation in a broad frequency range. The nonlinear properties of this system are based on the broad sized microdomain distribution appearing naturally in the as-grown crystal. The large angular deflection obtained for conical second harmonic generation allows considering this system as a nonlinear prism with variations in the second harmonic generation angle as large as 35° in the wavelength range of 430–660 nm.

Growth and characterization of Nd-doped Ca0.28Ba0.72Nb2O6 crystal

We report the growth of a Nd-doped calcium barium niobate (Nd:CBN-28) single crystal using the Czochralski method. The point group and space group of Nd:CBN-28 are determined to be tetragonal 4mm and P4bm, respectively, and the effective segregation coefficients of Nd, Ca, Ba, and Nb are 0.988, 1.029, 0.992, and 0.985, respectively. The density of the material is 5.321 g cm−3 at 19.6 °C, in good agreement with the theoretical value. Thermal expansion measurements reveal that during the heating cycle, the c-axis of Nd:CBN-28 undergoes both thermal contraction and thermal expansion, while at the same time there is only expansion along the a-axis. Specific heat measurements reveal that an anomaly appears at about 220 °C due to a phase transition. The thermal diffusivity increases slowly with increasing temperature. The thermal conductivity of the crystal has been calculated from these results, and the phonon mean free paths la and lc along the a- and c-axes of Nd:CBN-28 crystal are estimated. The transmissio...

Growth and thermal properties of Ga3PO7 bulk single crystals

Ga3PO7 crystal with large size and good optical quality has been grown by the top-seeded solution growth slow-cooling method from a Li2O–3MoO3 flux system. Thermal properties of the as-grown Ga3PO7 crystal have been carefully studied by measuring the anisotropic thermal expansion, specific heat, thermal diffusion, and thermal conductivity. The results show that Ga3PO7 crystal possesses low thermal expansion coefficients and good thermal conductivity. The calculated average thermal expansion coefficients along a and c axes are αa=1.66×10−6 and αc=3.53×10−6K−1 from 293.15to773.15K. The thermal conductivities along a and c axes are up to 6.34 and 6.18Wm−1K−1 at the temperature of 303.15K.

Growth and passively self-Q-switched laser output of new Nd 3+ ,Cr 5+ :GdVO 4 crystal

A new passively self-Q-switched Nd, Cr:GdVO(4) laser crystal was grown by Czochralski method for the first time to our knowledge. Polarized absorption spectra were measured at room temperature. The absorption bands display polarization character and an absorption band of Cr(5+) ions at 1110 nm enables the crystal to be a self-Q-switched laser material at 1.06 mum. In the passive self-Q-switching operation, the maximum output power, shortest pulse width, and largest pulse energy were obtained to be 265 mW, 230 ns, and 1.12 microJ, respectively.

Growth, electromechanical, and electro-optic properties of tungsten bronze (Ca0.28Ba0.72)0.25(Sr0.6Ba0.4)0.75Nb2O6 single crystal

A calcium strontium barium niobate (Ca0.28Ba0.72)0.25(Sr0.60Ba0.40)0.75Nb2O6 (CSBN25) single crystal has been grown using the Czochralski technique. The point group and space group of CSBN25 were determined by x-ray powder diffraction analysis to be tetragonal 4 mm and P4bm, respectively. The complete set of dielectric, piezoelectric, and elastic constants of CSBN25 have been determined by resonance techniques and impedance analysis at room temperature, and the relevant constants have been obtained and discussed. The relative dielectric constants are e11=343, and e33=502. Our results show that CSBN25 has excellent piezoelectric properties with d33=94.3, d31=−31.1, and d15=16.6 pC/N. The elastic compliance constants are s11=5.1, s12=−4, s13=1.4, s33=5.1, s55=13.2, and s66=19 pm2/N. The linear electro-optic coefficients of CSBN25 also have been measured by using an interferometric method. The results obtained are γ33=140, γ13=18, γ51=18, and γc=108.7 pm/V.

Diode-pumped Q-switched intracavity frequency-doubled Nd:LuVO4/KTP green laser

A simple and compact diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:LuVO4/KTP green laser were demonstrated successfully for the first time. At an incident pump power of 6.5 W, an average output power of 663 mW, a pulse width of 26 ns were obtained with a PRF of 10 kHz. The pulse energy and peak power of the green light were determined to be 66.3 μJ and 2.55 kW, respectively.

Cr 5+ :GdVO 4 as a saturable absorber for a diode-pumped Nd:Lu 0.5 Gd 0.5 VO 4 laser

A new Q-switched crystal Cr(5+):GdVO(4) was grown by the Czochralski method for the first time, to our knowledge. Polarized absorption spectra of Cr(5+)+:GdVO(4) were measured at room temperature. The results showed that the crystal has polarized absorption properties, and the absorption band of pi-polarized spectra located at 900 to 1300 nm should be suitable as a passive saturable absorber Q-switched laser at about 1 mum. With Cr(5+):GdVO(4) as a saturable absorber, the pulsed laser performance of Nd:Lu(0.5)Gd(0.5)VO(4) at 1.06 mum was demonstrated. The maximum average output power of 122 mW was obtained under a pump power of 3.79 W. The shortest pulse width and largest pulse energy obtained were 361 ns and 0.77 muJ, respectively. To our knowledge, it is the first time the absorption spectra of Cr(5+):GdVO(4) and a pulsed laser with the crystal as the saturable absorber have been obtained.