[en] Highlights: • A new yellow laser crystal Dy³⁺ doped GdScO₃ was grown successfully by Cz method. • The transition intensity parameters Ω_t are first obtained by J-O theory. • Dy:GdScO₃ has larger σ_α than Dy:YAG crystal and the FWHM at 453 nm is 9 nm. • Dy:GdScO₃ exhibits relatively long τ_f of 459 μs and high η of 70.6%. - Abstract: High-quality Dy³⁺ doped GdScO₃ (Dy:GdScO₃) single crystal was grown successfully by the Czochralski method for the first time. The lattice parameters of the as-grown crystal were obtained by Rietveld refinement to its XRD patterns. The effective segregation coefficient of Dy³⁺ is calculated to be 0.68. The spectroscopic characteristics of Dy:GdScO₃ are investigated, with special attention to the yellow emission that could be pumped directly by the rapidly developed blue GaN LD. The absorption cross section of Dy:GdScO₃ at 453 nm is 1.8 × 10^-21 cm² and the FWHM of this absorption band is about 9 nm at 300 K. Meanwhile, Dy:GdScO₃ exhibits strong yellow emission at 577 nm corresponding to the transition ⁴F_9/2→⁶H_13/2 with stimulated emission cross section of 4.1 × 10^-21 cm². The relatively long fluorescence lifetime (459 μs) and high radiative quantum efficiency of the ⁴F_9/2 level indicate a high laser efficiency of Dy:GdScO₃ crystal. All results suggest that Dy:GdScO₃ crystal could be a promising candidate for yellow laser at 577 nm pumped by blue GaN LD.

[en] The 1.5 at.% Er³⁺ doped gadolinium scandium gallium garnet (GSGG) laser crystal with high optical quality was successfully grown by the Czochralski method. The structural parameters were obtained by x-ray Rietveld refinement. A high crystalline quality of Er:GSGG was determined by x-ray rocking curve. The spectroscopic parameters of Er³⁺ ion were calculated and analyzed using the Judd–Ofelt theory. Furthermore, the stimulated-emission cross-section spectra were investigated for the ⁴I_13/2  →  ⁴I_15/2 transitions at 1.5–1.6 µ m, which indicates the great potential of Er:GSGG for multi-wavelength emission at 1.5–1.6 µ m. The larger emission cross-section and long fluorescence lifetimes around 0.55 and 0.67 µ m mean that the 1.5 at.% Er:GSGG crystal is beneficial for green and red laser generation. Meanwhile, the intensity of the emission spectra was compared between the 1.5 at.% and 2.0 at.% Er-doped GSGG. The roles of cross-upconversion, cross-relaxation and the excited-state absorption process were discussed in the 1.5 at.% Er:GSGG crystal for generating visible and 1.5–1.6 µ m lasers. (paper)

[en] Zinc oxide (ZnO) nanostructures are promising candidates as electronic components for biological and chemical applications. In this study, ZnO ultra-fine nanowire (NW) and nanoflake (NF) hybrid structures have been prepared by Au-assisted chemical vapor deposition (CVD) under ambient pressure. Their surface morphology, lattice structures, and crystal orientation were investigated by scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Two types of ZnO nanostructures were successfully integrated as gate electrodes in extended-gate field-effect transistors (EGFETs). Due to the amphoteric properties of ZnO, such devices function as pH sensors. We found that the ultra-fine NWs, which were more than 50 μm in length and less than 100 nm in diameter, performed better in the pH sensing process than NW–NF hybrid structures because of their higher surface-to-volume ratio, considering the Nernst equation and the Gouy–Chapman–Stern model. Furthermore, the surface coating of (3-Aminopropyl)triethoxysilane (APTES) protects ZnO nanostructures in both acidic and alkaline environments, thus enhancing the device stability and extending its pH sensing dynamic range. (paper)

[en] A novel mixed laser crystal of Nd:GdLaNbO₄ (Nd:GLNO) was grown successfully by conventional Czochralski method. The unit cell parameters were obtained by Rietveld refinement method. The density of the as-grown crystal was measured by Archimedean buoyancy method and calculated in theory. Absorption spectrum of Nd:GLNO crystal was recorded at room temperature, and 11 absorption peaks were assigned. The defects of Nd:GLNO crystal were revealed by using chemical etching method with phosphoric acid as etchant. The mechanical properties (including hardness, yield strength, elastic stiffness constant, fracture toughness and brittleness index) were systemically estimated based on Vickers hardness test. All these obtained results play a quite important role in further investigation of Nd:GLNO crystal. (orig.)

[en] The Judd–Ofelt theoretic transition intensity parameters of luminescence of rare-earth ions in solids are important for the quantitative analysis of luminescence. It is very difficult to determine them with emission or absorption spectra for a long time. A “full profile fitting” method to obtain in solids with its emission spectrum is proposed, in which the contribution of a radiative transition to the emission spectrum is expressed as the product of transition probability, line profile function, instrument measurement constant and transition center frequency or wavelength, and the whole experimental emission spectrum is the sum of all transitions. In this way, the emission spectrum is expressed as a function with the independent variables intensity parameters , full width at half maximum (FWHM) of profile functions, instrument measurement constant, wavelength, and the Huang–Rhys factor S if the lattice vibronic peaks in the emission spectrum should be considered. The ratios of the experimental to the calculated energy lifetimes are incorporated into the fitting function to remove the arbitrariness during fitting and other parameters. Employing this method obviates measurement of the absolute emission spectrum intensity. It also eliminates dependence upon the number of emission transition peaks. Every experiment point in emission spectra, which usually have at least hundreds of data points, is the function with variables and other parameters, so it is usually viable to determine and other parameters using a large number of experimental values. We applied this method to determine twenty-five of Yb³⁺ in GdTaO₄. The calculated and experiment energy lifetimes, experimental and calculated emission spectrum are very consistent, indicating that it is viable to obtain the transition intensity parameters of rare-earth ions in solids by a full profile fitting to the ions’ emission spectrum. The calculated emission cross sections of Yb³⁺:GdTaO₄ also indicate that the F–L formula gives larger values in the wavelength range with reabsorption. (paper)

[en] A mixed laser crystal of Nd-doped GYNO crystal was grown successfully by Czochralski method. The crystal belongs to monoclinic system with space group I2/a, the structural parameters are obtained by the X-ray Rietveld refinement method. The defects and dislocations along three crystallographic orientations were studied by using the chemical etching method with the phosphoric acid etchant. The mechanical properties (including hardness, yield strength, fracture toughness, and brittle index) of the crystal were estimated by Vickers hardness test. The transmission spectrum was measured at room temperature, and the absorption peaks were assigned. Spectral properties of the as-grown crystal were investigated by Judd-Ofelt theory, and the Judd-Ofelt intense parameters Ω_2_,_4_,_6 were obtained to be 9.674 x 10"-"2"0, 2.092 x 10"-"2"0, and 4.061 x 10"-"2"0 cm"2, respectively. (orig.)

[en] A Nd-doped GdNbO_4 crystal was grown successfully by Czochralski method. Its monoclinic structure was determined by X-ray diffraction; the unit-cell parameters are a = 5.38 Aa, b = 11.09 Aa, c = 5.11 Aa, and β = 94.56 . The morphological defects of Nd:GdNbO_4 crystal were investigated using the chemical etching with the phosphoric acid etchant. For a new crystal, the physical properties are of great importance. The hardness and density of Nd:GdNbO_4 were investigated first. Thermal properties of Nd:GdNbO_4, including thermal expansion coefficient and specific heat, were measured along a-, b-, and c-crystalline axes. Thermal properties indicate that the Nd:GdNbO_4 pumped along c-axis can reduce the thermal lensing effect effectively. The specific heat is 0.53 J g"-"1 K"-"1 at 300 K, indicating a relatively high damage threshold of Nd:GdNbO_4. The transmission and emission spectrum of Nd:GdNbO_4 were measured, and the absorption peaks were assigned. The strongest emission peak of Nd:GdNbO_4 is located at 1065.3 nm in the spectral range of 850-1420 nm excited by 808 nm laser. The refractive index of Nd:GdNbO_4 was calculated with the transmission spectrum and fitted with Sellmeier equation. All these obtained results is of great significance for the further research of Nd:GdNbO_4. (orig.)

[en] A Nd-doped niobate mixed laser crystal of Nd_0.01:Gd_0.89La_0.1NbO₄ (Nd:GLNO) has been grown successfully by Czochralski method. The absorption spectrum, fluorescence spectrum and fluorescence decay curve of Nd:GLNO crystal were measured at room temperature. The spectral parameters of Nd:GLNO crystal were obtained based on Judd-Ofelt (J-O) theory calculation. The three intensity parameters Ω_{t(t=2, 4, 6)} were calculated to be 6.61, 1.43 and 3.31 × 10^-20 cm², respectively. On the base of the Ω_t calculation, the branching ratios, spontaneous radiative probabilities, radiative lifetime and fluorescence quantum efficiency of the ⁴F_3/2 level have been evaluated. Compared with other Nd-doped niobate laser crystal, Nd:GLNO shows a special spectral properties due to the large structure disorder caused by La³⁺. All the results demonstrate that this crystal is a specific low symmetrical laser material different from other niobates family crystals such as Nd:GdNbO₄ (Nd:GNO) and Nd:YNbO₄ (Nd:YNO) and can be considered as a promising laser material suitable for laser diode pumping.

[en] Highlights: • Dy:YAG and Dy,Tb:YAG with high quality were grown with Cz method. • Thermal properties of Dy:YAG were revealed. • Spectroscopic properties as well as energy transfer mechanism between Dy³⁺ and Tb³⁺ were discussed. • The results indicate that Dy:YAG and Dy,Tb:YAG crystals can be appraised as excellent competitors for yellow laser. With the fast development of GaN blue laser diode, Dy³⁺ doped laser crystals are receiving renewed interests due to their potential yellow laser emission under GaN laser diode pumping. In this study, Dy:YAG and Dy,Tb:YAG with high quality have been grown successfully with Czochralski method. Their spectroscopic properties as well as the energy transfer mechanism between Dy³⁺ and Tb³⁺ were discussed in details. The 583 nm emission cross-section of Dy:YAG crystal is improved by co-doping of Tb³⁺, which indicates the efficient quasi-resonant energy transfer between the Dy³⁺-⁶H_13/2 state and Tb³⁺-⁷F₄ state is realized. The thermal properties of Dy:YAG, including specific heat and thermal conductivity, were investigated. The high thermal conductivity suggests the Dy:YAG crystal should be very suitable for high-power laser operation. In addition, considering the high phonon energy of Dy:YAG and Dy,Tb:YAG crystals, the depletion of population on the lower laser level (⁶H_13/2) of Dy³⁺ could be accelerated. The results suggesting that both Dy:YAG and Dy,Tb:YAG could be highly appraised as excellent competitors for all solid state yellow lasers.

[en] Highlights: • A novel laser crystal Sm:GLSO was grown by Czochralski method. • Its spectral properties were investigated systematically. • The J-O calculation was performed on the crystal and three J-O parameters were obtained. • The crystal is very promising for realizing orange–yellow laser operation using LD pumping. -- Abstract: Recently, an intense interest has been aroused for Sm³⁺-doped laser crystals which are able to realize visible reddish-orange laser directly using semiconductor laser pumping. In this study, a mixed Sm³⁺-doped Sm_0.02Gd_1.88La_0.1SiO₅ (Sm:GLSO) laser crystal was grown successfully by Czochralski method. The structure of the as-grown crystal was determined with X-ray diffraction. The as-grown crystal exhibits large absorption cross section (1.53 × 10⁻²⁰ cm²) at around 405 nm, indicating that it can be pumped efficiently by the commercialized GaN/InGaN laser diode. Three Judd-Ofelt intensity parameters Ω_t (t = 2, 4, 6) were calculated to be 5.177, 3.783 and 2.218 × 10⁻²⁰ cm², respectively. The stimulated emission cross section at 614 nm was calculated to be 0.471 × 10⁻²⁰ cm² and the fluorescence lifetime for ⁴G_5/2 level was fitted to be 1.90 ms. All these results suggest that Sm:GLSO is very promising for realizing reddish-orange laser operation using the current commercialized GaN/InGaN laser diode pumping.