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Two distinct compositions of mixed garnet crystals, codoped with Dy3+ and Tb3+ ions, were grown using the Czochralski method. The structures and thermal properties of these crystals were thoroughly examined, and the influence of the doped ions on their structure and thermal properties was analyzed. Additionally, a straightforward and reliable method was introduced for accurately determining the specific heat and thermal diffusivity of garnet crystals across a wide temperature range, extending from room temperature to elevated temperatures. The absorption properties of the crystals were investigated, and their bandgap energies were determined using the Tauc formula. The relationship between the bandgap energy of garnet crystals and the radius of cations corroborates Yadav's prediction. Furthermore, the emission characteristics of the crystals under blue, UV, and VUV excitation were thoroughly studied. A proposed mechanism for energy transfer between Dy3+ and Tb3+ ions in the mixed garnet crystals was elucidated based on the absorption and emission characterization. The results indicate that the mixed garnet crystals exhibit distinct advantages for the development of blue laser diode pumped yellow lasers. Overall, this study provides valuable insights into the structural, thermal, optical, and energy transfer properties of mixed garnet crystals, highlighting their potential applications in all solid-state yellow laser technology. [ABSTRACT FROM AUTHOR]

Exploring new visible laser crystals is of great significance to the development of diode pumped all-solid-state visible lasers and solid-state lighting. In this work, a high concentration (10 at%) Er3+ ion singly doped GdTaO4 single crystal with high quality as a promising visible laser crystal was grown successfully by the Czochralski method. The structure of the crystal was determined to be a monoclinic structure with the space group C2/c by powder and single-crystal X-ray diffraction characterization techniques. The absorption and blue and violet light excited emission spectra of the crystal were obtained and analyzed. A strong emission band centered at 555 nm was observed under excitation at both 450 nm and 377 nm. The absorption cross-section at 450 nm and emission cross-section at 555 nm were calculated to be 4.60 × 10−21 and 4.57 × 10−21 cm2, respectively, which are comparable to those of other promising InGaN diode pumped visible laser crystals doped with rare earth ions (Er3+, Dy3+ and Pr3+). Under 450 nm or 355 nm laser excitation, the crystal emits strong green fluorescence. A 380 nm LED chip pumped prototype device was fabricated using the crystal, which exhibited green light under the driving current. Besides, the green and red upconversion luminescence of Er3+ in the GdTaO4 single crystal was found to be a two-photon process under the excitation of a 980 nm laser. All these results strongly recommend that the 10 at% Er3+ ion doped GdTaO4 crystal is very promising for diode pumped green lasers and probably useful for solid-state lighting. [ABSTRACT FROM AUTHOR]

Abstract A promising 2.9 µm Ho:GdYTaO 4 laser crystal was grown successfully by the Czochralski method for the first time. The crystal belongs to the monoclinic space group of I 2/a (No. 15) and high crystalline quality is demonstrated by X-ray rocking curves. The spectral properties of Ho:GdYTaO 4 crystal at room temperature are investigated. Based on the Judd–Ofelt theory, the intensity parameters, spontaneous transition probabilities, fluorescence branching ratios, and radiative lifetimes are obtained in detail. The strongest emission peak is located at 2848 nm, and the full width at half maximum is about 15 nm. The experimental lifetimes of 5 I 6 and 5 I 7 levels are 0.31 and 8.08 ms, respectively. Moreover, the Stark levels of 5 I 6 , 5 I 7 , and 5 I 8 are identified and the splitting values are calculated to be 254.1, 226.7, and 370. 4 cm−1, respectively. [ABSTRACT FROM AUTHOR]

A novel mixed laser crystal of Nd:GdLaNbO (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. [ABSTRACT FROM AUTHOR]

Tb 3 Sc 2 Al 3 O 12 (TSAG) magneto-optical crystal was grown successfully by the Czochralski (Cz) method. Its structure and crystalline quality were determined by the powder X-ray diffraction and X-ray rocking curve, respectively. The chemical etching method was employed to investigate its defects morphology with phosphoric acid as etchant. Based on the Vickers hardness experiment, the mechanical properties of TSAG crystal (including hardness, yield strength, fracture toughness and brittle index) were systematically estimated. The thermal properties of TSAG crystal in the temperature range of 280–500 K were obtained for the first time, which are valuable for evaluating its applications. The transmission spectrum of the as-grown crystal was measured at room temperature and the transmittance in the wavelength range of 505–1445 nm is found to be as high as 82.3%. All the obtained results will contribute significantly to exploring TSAG crystal that used in high-average-power magneto-optical systems. [ABSTRACT FROM AUTHOR]

A new promising 2.9 μm Tm,Ho:GdYTaO 4 (Tm,Ho:GYTO) laser crystal was grown by the Czochralski method. The full width at half maximum (FWHM) of X-ray rocking curve on the (0 1 0) face is only 0.05°, which indicates that the crystal has high crystalline quality. The structure parameters of Tm,Ho:GYTO crystal were determined by Rietveld refinement method. Chemical etching is employed to investigate the defect structure of Tm,Ho:GYTO crystal with KOH etchant. The absorption, emission spectra, and level lifetimes were measured, and the corresponding absorption transitions were assigned. The absorption cross-section at 790 nm was calculated to be 2.04 × 10 −20 cm 2 and maximum emission-cross section at 2932 nm was 2.05 × 10 −20 cm 2 . The level lifetimes of 5 I 6 and 5 I 7 are 131 μs and 4.09 ms, respectively. Compared with other hosts, such as Ho:YAG, the shorter lifetime of 5 I 7 and long lifetime of 5 I 6 in the Tm,Ho:GYTO crystal are easier to realize population inversion. The Tm–Ho energy transfer mechanism in GYTO is also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Eu:Gd3Sc2Ga3O12 powder was synthesized by co-precipitation method with metal Ga, Eu2O3, Gd2O3, Sc2O3 as starting materials and aqueous ammonia as precipitator. X-ray diffraction (XRD), the Rietveld refinement method and transmission electron microscope (TEM) were employed to study the crystal structure. The fluorescent spectra and decay curves were used to investigate the luminescence properties of the resulting powders. The XRD spectra and results of the Rietveld refinement indicated that the structure of Gd3Sc2Ga3O12 hardly changed and only crystal lattice distorted a little when Eu3+ ion was doped. The transmission electron microscope (TEM) observation and XRD line broadening calculation revealed that the particle size of Eu:Gd3Sc2Ga3O12 powder increased with the increase of the calcination temperature. At the same time, the emission intensity and lifetime of Eu:Gd3Sc2Ga3O12 powder also increased with the calcination temperature. In the emission spectra, a 590nm orange line from 5D0 → 7F1 as the most prominent group meaned that Eu3+ ion mainly occupied the inversion center in Gd3Sc2Ga3O12 crystal which may be caused by a small number of Gd atoms entered the 16(a) site. [Copyright &y& Elsevier]

Abstract Er, Pr co-doped GSAG laser crystal with high optical quality was successfully grown by the Czochralski method for the first time. X-ray rocking curve exhibit the high crystalline quality of this crystal. The intensities of optical transmission and luminescence of Er,Pr:GSAG crystal were not deteriorate after the gamma-ray irradiation even with a dose of 1.16 × 106 Gy, confirming the excellence radiation resistant property of Er, Pr:GSAG crystals. The efficiencies of energy transfer from 4I 11/2 to 1G 4 and 4I 13/2 to 3F 4 between Er3+ and Pr3+ ions in GSAG crystal are determined as 16.7% and 94.9%, which indicate that the Pr3+ can act as an deactivator ions for Er3+ ions in Er,Pr:GSAG crystal. Additionally, the luminescence spectra of Er,Pr:GSAG crystal are compared with that of Er:GSAG crystal in the visible and near-IR regions, which provided that Pr3+ ions can efficiently depopulate the 4I 13/2 level and reduce the fluorescence lifetime. All the results demonstrate that Er,Pr:GSAG crystal can realize multi-wavelength laser output at 2.6–2.9 μm under harsh radiation environment. Highlights • Heavily Er,Pr:GSAG laser crystal was grown successfully by the Czochralski method for the first time. • The fluorescence intensity and lifetimes of these crystals does not deteriorate under the gamma-ray irradiation even with a dose of 1.16×106 Gy, indicating the excellence radiation resistance properties of Er, Pr:GSAG crystal. • Pr3+ deactivator can inhibit effectively the self-termination phenomenon, and population inversions can be realized at a lower pumping threshold. • Four strongest fluorescence peaks of the two crystals are located at 2621, 2695, 2793, and 2827 nm, corresponding to the 4I 11/2. → 4I 13/2 level transitions of Er3+ ions. Er, Pr:GSAG crystals can be realize multi-wavelength laser output at 2.6–2.9 μm under harsh radiation environment. • The luminescence spectra in the visible and near-IR regions are studied and analyzed, which provide a further evidence that Pr3+ ions can efficiently depopulate the 4I 13/2 level and reduce the fluorescence lifetime. [ABSTRACT FROM AUTHOR]

1 at% Er 3+ doped Er: GdTaO 4 laser crystal with high optical quality was successfully grown by the Czochralski method. The structural parameters were obtained by the X-ray Rietveld refinement. A high crystalline quality of Er: GdTaO 4 was determined by the X-ray rocking curve. The transition intensity parameters of Er 3+ ions were fitted according to the absorption spectra along three principal polarization directions. The relatively larger emission cross section (1.022×10 −20 cm 2 ), long fluorescence lifetime ( 5.66 ms) and relatively weaker reabsorption phenomenon around 1.6 µm indicate that 1 at% Er: GdTaO 4 crystal can be used as a promising NIR laser material. Meanwhile, the stimulated emission cross-section spectra along three principal polarization directions were investigated for 4 I 13/2 → 4 I 15/2 transitions at 1.5–1.6 µm which indicates a great potential of Er: GdTaO 4 for multi-wavelength emission at 1.5–1.6 µm. In addition, the possibility of generating green and red lasers in Er: GdTaO 4 was also analyzed and evaluated. [ABSTRACT FROM AUTHOR]

We have demonstrated continuous wave (CW) laser operation of Nd:YNbO 4 crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10 −20 cm 2 ) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10 −20 cm 2 ) and relative long lifetime of the 4 F 3/2 → 4 I 11/2 transition indicates good energy storage capacity of Nd:YNbO 4 . Moreover, the raw materials of Nd:YNbO 4 are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO 4 crystal is a potentially new laser material suitable for LD pumping. [ABSTRACT FROM AUTHOR]

A new crystal of Yb-doped gadolinium niobate, 5 at.% Yb:GdNbO 4 , is grown by Czochralski method for the first time. The structure of Yb:GdNbO 4 is determined by Rietveld refinement to the X-ray powder diffraction data and it belongs to the monoclinic space group of I 2/a . With the center of 955 nm, the FWHM of absorption spectra is 57 nm and the absorption cross section is calculated to be 0.97 × 10 −20 cm 2 . Spectral parameters are calculated with absorption spectrum. In emission spectra, the strongest peak is at 1001 nm and the FWHM is 49 nm. In comparison with corresponding emission cross section of Yb:YSO and Yb:GSO, Yb:GdNbO 4 exhibits a relatively larger emission cross section. In addition, a maximal output power of 270 mW is obtained and the slope efficiency is 7.5%. [ABSTRACT FROM AUTHOR]

A great potential mid-infrared laser crystal of heavily Er3+ doped GSAG crystal with high optical quality is successfully grown by Cz method. The crystal quality of Er:GSAG crystal is determined by XRC. The structure parameters of Er:GSAG crystal are obtained by the X-ray Rietveld refinement method (a = b = c = 12.3196 Å). The absorption cross section at 961 nm and 967 nm are 0.381 × 10−21 cm2 and 0.414 × 10−21 cm2, respectively. The 962 nm laser diode end-pumped Er:GSAG laser operated at 2828 nm is demonstrated for the first time. The performance of Er:GSAG laser is investigated in great detail. A maximum output power of Er:GSAG laser is 410 mW when pumped by 962 nm LD at 300 Hz and 0.5 ms. Simulating results display the highest temperatures of Er:GSAG laser spot is 345.8 K, indicating a small thermal lensing effect of Er:GSAG crystal. Besides, the laser performance of Er:GSAG crystals which irradiate by different doses of gamma-ray are used to investigated its potential for working in the radiation resistance environment. The results show the relatively minor differences on the Er:GSAG lasers performance, indicating a great potential of Er:GSAG crystal in radiant environment application. • Er:GSAG laser operate at 2828 nm by 962 nm LD end-pumped is reported for the first time. • A potential mid-infrared laser crystal of Er:GSAG is successfully grown by Cz method. • The structure parameters of Er:GSAG crystal are investigated by the XRD for the first time. • A maximum output power of 410 mW was obtained with Er:GSAG laser. • The Er:GSAG laser indicate a great potential in radiant environment application. [ABSTRACT FROM AUTHOR]