Single ABC3O7 crystals with the melilite structure, including SrLaGa3O7, SrGdGa3O7, and BaLaGa3O7, have been successfully grown by the Czochralski method. A complete set of room temperature elastic, dielectric, and piezoelectric constants was determined using resonance techniques and impedance analysis. Our results indicate that the crystals exhibit superior piezoelectric and elastic properties. The electrical resistivity was found to be on the order of 6 × 1013 ohm·cm at room temperature. The dielectric permittivity ε11, piezoelectric constant d14, and electromechanical coupling coefficient k′12 were found to be on the order of 15–17, 12–15 pC/N, and 16–19%, respectively. For an ABC3O7 group member such as SrLaGa3O7, the melting temperature was measured to be 1588 °C, below which the crystal maintains good thermal stability. Consequently, the piezoelectric properties were studied as a function of temperature over the range of −50 to 120 °C. The frequency vs temperature coefficient was determined to be −16 to −55 ppm/K, depending on orientation. The dielectric permittivity, piezoelectric constant, and electromechanical coupling coefficient showed good temperature stability. The absence of any phase transitions below their melting points (on the order of 1600 °C) makes the ABC3O7 family promising candidate materials for high temperature piezoelectric applications.

A Nd:Bi12SiO20 crystal was grown by the Czochralski method. The thermal properties of the crystal were systematically studied. The thermal expansion coefficient was measured to be α=11.42×10−6 K−1 over the temperature range of 295–775 K, and the specific heat and thermal diffusion coefficient were measured to be 0.243 Jg−1 k−1 and 0.584 mm2/s, respectively at 302 K. The density was measured to be 9.361 g/cm3 by the buoyancy method. The thermal conductivity of Nd:Bi12SiO20 was calculated to be 1.328 Wm−1 K−1 at room temperature (302 K). The refractive index of Nd:Bi12SiO20 was measured at room temperature at eight different wavelengths. The absorption and emission spectra were also measured at room temperature. Continuous-wave (CW) laser output of a Nd:Bi12SiO20 crystal pumped by a laser diode (LD) at 1071.5 nm was achieved with an output power of 65 mW. To our knowledge, this is the first time LD pumped laser output in this crystal has been obtained. These results show that Nd:Bi12SiO20 can serve as a laser crystal.

A new series Nd:Lu3ScxGa5 − xO12 (x = 0.5, 0.8, 1, 1.2 and 1.5) laser crystals have been successfully grown by the optical floating zone method. Their absorption and luminescence spectra were measured at room temperature and spectral parameters were systemically calculated using Judd–Ofelt (JO) theory. The fluorescence τf lifetimes were experimentally measured and compared with the theoretical results. Diode-pumped continuous-wave (CW) laser performance at 1.06 μm with mixed crystals was demonstrated. The influence of different x values on laser performance and spectral parameters was also discussed. All the results show that Nd:Lu3ScxGa5 − xO12 series crystals should be suitable for laser application.

Novel tetragonal scandium orthovanadate crystals doped with neodymium ions (Nd:ScVO4) have been successfully grown with the floating zone (FZ) method for applications in photonic devices. High-temperature stability studies and X-ray structural studies show that thermally induced vanadium oxide vaporization triggers a series of topological transitions from the rutile lattice to the defect fluorite lattice when crystallization begins in the ScVO4 melt. Besides zircon-type ScVO4 and bixbyite-type Sc2O3, a third form with metallic properties called tetragonal Sc2VO5 was thus obtained. Ab initio calculations further reveal that such structural transitions at high-temperature are directly driven by increasing covalency in the scandium−oxygen bonds and are energetically favored. In addition, the anisotropic mechanical and optical properties of ScVO4, such as elastic stiffness, Young’s modulus, dielectric constants, and refractive index, were calculated using density functional theory and evaluated for future applications. The calculated results tend to support the experimental data.

Graphene grown by thermal decomposition of a two-inch 6H silicon carbide (SiC) wafers surface was used to modulate a large energy pulse laser. Because of its saturable absorbing properties, graphene was used as a passive Q-switcher, and because of its high refractive index the SiC substrate was used as an output coupler. Together they formed a setup where the passively Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal laser was realized with the pulse energy of 159.2 nJ. Our results illustrate the feasibility of using graphene as an inexpensive Q-switcher for solid-state lasers and its promising applications in integrated optics.Keywords: composites; graphene; laser; Q-switcher

Li2B4O7 polycrystalline films on silica glass and Si(111) substrates were prepared by chemical solution decomposition(CSD) method. After spin coating, the wet film was dried at 200 °C, and then annealed at different temperatures to form polycrystalline Li2B4O7 film. These annealed films were characterized by using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscope (TEM) and selective area electron diffraction (SAED). All these results show that the main component of the film is Li2B4O7 crystalline phase and the average crystalline size of these films is in the range of 20–50 nm.

Nd:LuVO4 single crystal has been grown by Czochralski method. Optical absorption bands of Nd:LuVO4 crystal have been measured and assigned to transitions between the energy levels of Nd3+. From the optical absorption measurements, intensity parameters (Ωt (t = 2, 4, 6)) have been calculated and the results were Ω2 = 7.182 × 10−20, Ω4 = 5.990 × 10−20 and Ω6 = 5.779 × 10−20 cm2 by using Judd–Ofelt theory, respectively. Radiative lifetimes (τrad.), branching ratios of the fluorescence emission (βJ″J′βJ″J′) and the integrated emission cross-section ∑(J″→J′)∑(J″→J′) have also been theoretically estimated and reported for certain fluorescent levels. The thermal, optical and laser properties of Nd:LuVO4 crystal are compared with those of Nd:YVO4 and Nd:GdVO4 crystals, and the results show that Nd:LuVO4 crystal is a potential laser crystal.

High quality Nd-doped lutecium vanadate thin films on silica glass substrates were fabricated successfully by using a pulsed laser deposition technique. The properties of the samples were characterized by using X-ray diffraction, Rutherford backscattering, atomic force microscopy (AFM), and prism-coupling measurements. The RBS shows that the ratio of Lu/V in the film is 0.991, which is in good agreement with the target composition. X-ray diffraction results show that the degree of crystal orientation along (2 0 0) increases with increasing oxygen pressure up to 20 Pa. The refractive indices of the films determined with dark-mode prism coupling measurements are slight, smaller than that of the bulk crystal. An optimum 20 Pa oxygen pressure, at which the oxygen was leaked into the chamber as the reactive ambient, was determined.

The crystal growth of vanadate crystals is realised. Nd:YVO4, Nd:GdVO4 and Nd:GdxLa1−xVO4 (x=0.80, 0.60, 0.45) are determined effective segregation coefficients and laser properties of these crystals. All the crystals have the zircon structure with the space group of I41/amd. We find the Nd:YVO4 crystal is the easiest one to grow among these crystals, the laser and thermal properties of Nd:GdVO4 are the best, and Nd:GdxLa1−xVO4 (x=0.80, 0.60, 0.45) crystals are the most difficult to be grown among the vanadate crystals. Under the pumping power of a 3 W laser diode, output powers of 1.27 W at 1.06 μm and 800 mW at 1.34 μm for the Nd:GdVO4 crystal, 1.14 W at 1.06 μm and 780 mW at 1.34 μm for the Nd:YVO4 crystal, and 1.18 W at 1.06 μm and 671 mW at 1.34 μm for the Nd:Gd0.8La0.2VO4 crystal were obtained, and intracavity frequency-doubling to 532 and 670 nm was also demonstrated using KTiOPO4 and LiB3O5 crystals.

The laser outputs of 1.26, 0.95, 0.5 and 0.32 at% Nd-doped concentrations in Nd:YVO4 crystal samples were performed under high pumping power of laser diode. The reason of different Nd-doped concentrations in Nd:YVO4 crystals influencing on the laser output properties was explained. The intracavity double frequency laser outputs of Nd:YVO4 crystal at 532 and 671 nm were also performed. Our experimental results show that the optimum Nd-doped concentration in Nd:YVO4 crystal is about 0.5 at% under a pumping power of 30 W.

A scandium orthovanadate (ScVO4) single crystal doped with Nd at a concentration of 0.5 at% with dimensions of ϕ8×35 mm2 has to our knowledge for the first time been successfully grown by the floating zone method. The absorption spectrum was measured at room temperature, showing that the transition from 4I9/2 to 4F5/2+2H9/2 is centered at 810 nm with FWHM 6.9 nm. Laser performance of the Nd:ScVO4 crystal at 1068 nm was demonstrated. A maximum average output power of 240 mW was achieved under a pump power of 5.19 W.

The disordered laser crystal neodymium-doped calcium lithium niobium gallium garnet (Nd:CLNGG) was successfully grown by the Czochralski method. Its thermal properties, including the average linear thermal expansion coefficient, thermal diffusion coefficient, specific heat, and thermal conductivity were measured, and continuous-wave (CW) laser performance at 1.06 μm was demonstrated. The maximum power of 1.48 W was achieved with corresponding optical conversion efficiency of 12.4% and slope efficiency of 16.2%.

Neodymium (Nd) doped lutetium gallium garnet (Nd:Lu3Ga5O12, Nd:LuGG) single crystal was successfully grown by the optical floating-zone method for the first time to our knowledge. Its absorption and luminescence spectra at room temperature were measured. By using the J–O theory, the spectral parameters of Nd:LuGG were calculated, which indicated that Nd:LuGG should possess comparable and even better laser properties than Nd:YAG. The maximum output power of 855 mW at 1062 nm was achieved with slope efficiency of 23.4% under a pump power of 5.2 W, and optical conversion efficiency of 16.4%. All the results show that Nd:LuGG is a potential laser material.