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Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10−20 cm2 for σ polarization and 5.32 × 10−20 cm2 for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10−20 cm2 at 980 nm for σ polarization and 2.28 × 10−20 cm2 at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at 2F5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y3+ in the crystal is partially replaced by Lu3+ and Gd3+, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals. [ABSTRACT FROM AUTHOR]

Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a "dirty" solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)3], can yield single-phase, epitaxial, and superconducting Sr2RuO4 films with the same ease and control as III–V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru4+ oxidation, the use of the Ru(acac)3 precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials. [ABSTRACT FROM AUTHOR]

Dy3+-doped CaF2-SrF2 crystals with various Dy3+ dopant concentrations were synthesized by multicrucible temperature gradient technology (MC-TGT). Dy:CaF2-SrF2 crystals were fluorite structured and crystallized in cubic F m 3 ¯ m space group, as characterized by X-ray diffraction. The crystallographic site concentration was calculated from the measured density by Archimedes' hydrostatic weighing principle. The optical transmission reached over 90% with a sample thickness of 1.0 mm. The Sellmeier dispersion formula was obtained following the measured refractive index in a mid-IR range of 1.7–11 μm. Absorption coefficients of 6.06 cm−1 and 12.71 cm−1 were obtained at 804 nm and 1094 nm in 15% Dy:CaF2-SrF2 crystal. The fluorescence spectra of 15 at.% Dy:CaF2-SrF2 showed the strongest wavelength peak at 2919 nm with a full width at half maximum (FWHM) of 267 nm under an excitation wavelength of 808 nm. The fluorescence lifetimes were illustrated for different Dy3+ dopant levels of 5%, 10% and 15%. The results indicate that the Dy:CaF2-SrF2 crystal is a promising candidate for compact mid-IR lasers. [ABSTRACT FROM AUTHOR]

Ho,Pr:CaYAlO 4 (Ho,Pr:CYA) crystal doped with 1 at.% Ho3+ and 0.1 at.% Pr3+ was successfully grown using the Czochralski method. Polarized absorption spectra, emission spectra, and fluorescence lifetime measurements were performed. The impact of Pr3+ co-doping on the ∼3 μm emission of Ho3+ ions was analyzed. The energy transfer efficiency from Ho3+:5I 7 to Pr3+:3F 2 energy level was calculated to be 60.66 %, indicating that Pr3+ effectively mitigated the self-termination effect in Ho,Pr:CYA crystals. The absorption cross-section at 645 nm was found to be 1.53 × 10−20 cm2 for σ polarization and 2.62 × 10−20 cm2 for π polarization. The emission cross-section at 2842 nm was calculated to be 0.86 × 10−20 cm2 for σ polarization and 1.33 × 10−20 cm2 for π polarization at 2908 nm, with a full width at half maximum (FWHM) of 139 nm and 88 nm, respectively. The fluorescence lifetimes of the 5I 6 and 5I 7 levels were measured to be 0.17 ms and 2.01 ms, respectively. These results collectively suggest that Ho,Pr:CYA crystals hold great potential as a candidate for 2.8 μm laser applications. • Ho3+,Pr3+ co-doped CaYAlO 4 crystal was grown by the Czochralski method. • The crystal structure, polarized absorption and emission spectra were investigated. • The intensity parameters were obtained using J-O theory. [ABSTRACT FROM AUTHOR]

• Spectral properties and high-efficiency broadband laser operation of Tm:CYGA crystal at 2 μm were demonstrated. • The maximum continuous-wave output power of 1.43 W was obtained. • A 284.7 nm tuning coverage was realized with a BF. We report on spectral properties and a high-efficiency broadband laser operation of Tm:CaY 0.9 Gd 0.1 AlO 4 (Tm:CYGA) crystal. The polarized absorption and emission spectra, gain cross sections and fluorescence lifetime are systematically studied, presenting a broad absorption and emission spectra and thus a smooth gain band. Furthermore, under an absorbed pump power of 4.35 W, a maximum continuous-wave (CW) laser output power of 1.43 W at 1967.8 nm is obtained, corresponding to a slope efficiency of 42.2 %. The beam quality factors (M2) in X-axis and Y-axis are measured to be 1.011 and 1.027, respectively. A tunable Tm:CYGA laser with a tuning range of 284.7 nm from 1837.5 to 2122.2 nm is achieved employing a birefringent filter (BF). The results indicate that the Tm:CYGA crystal is an excellent laser medium for generating high-efficiency broadband CW laser, indicating its potential for ultrashort pulse generation in the 2-μm spectral range. [ABSTRACT FROM AUTHOR]

In this paper, the Floating zone technique was used to grow high-quality Cr3+:YScO 3 crystals. The absorption cross-sections of the 4A 2 →4T 1 transition and 4A 2 →4T 2 transitions were calculated to be 1.71 × 10−20 cm2 at 488 nm and 0.72 × 10−20 cm2 at 666 nm, respectively. The crystal field strength Dq, Racah parameters B, and C were calculated to be 1502 cm−1, 533 cm−1, and 3362 cm−1, respectively. In the Cr3+:YScO 3 crystal, the effective phonon energy and Huang-Rhys factor S were calculated to be 284 cm−1 and 8.62, respectively. The emission cross-section at 988 nm corresponding to the 4T 2 →4A 2 transition was calculated to be 1.44 × 10−20 cm2 with full width at half maximum (FWHM) of 318 nm. All the results show that Cr3+:YScO 3 crystal has the potential to be a tunable and ultrafast laser crystal. • Cr:YScO 3 crystals were successfully grown by the Floating zone technique(FZ) method. • Broad emission spectrum with full width at half maximum (FWHM) of 318 nm in Cr:YScO 3 crystals was observed. • Spectral properties and crystal field parameters of Cr:YScO 3 crystals were investigated and analysed. [ABSTRACT FROM AUTHOR]

The polarization absorption spectra of Pr3+-doped GdScO 3 have been measured. Polarized emission spectra and fluorescence decay from the 3P 0 upper level have been investigated. The strongest absorption peaks are located at 448 nm for a, b and c polarization, the absorption cross sections are 1.29 × 10−20 cm2, 0.98 × 10−20 cm2 and 1.57 × 10−20 cm2, respectively. The maximum emission cross section is located at 662 nm, which is 18.55 × 10−20 cm2 (a polarization), 12.74 × 10−20 cm2 (b polarization) and 22.41 × 10−20 cm2 (c polarization), and the FWHM is 10.02 nm, 9.38 nm and 10.14 nm, respectively. The fluorescence lifetime of 3P 0 level is 12.39 μs. Those results indicated that Pr3+-doped GdScO 3 crystal grown by the Czochralski method is a potential laser medium for visible laser operation. •The spectra of Pr:GdScO 3 have been measured at room temperature. •Pr3+-doped GdScO 3 crystal is a potential laser medium for 662 nm laser. [ABSTRACT FROM AUTHOR]

Ce,Tb,Gd:YAG-Al 2 O 3 eutectic crystal phosphor plates (ECPPs) were grown by the micro-pulling-down (μ-PD) method to adjust correlated color temperature (CCT) and color rendering index (Ra) for high-power warm white LED applications. Tb3+ and Gd3+ ions in Ce:YAG-Al 2 O 3 play a positive role in spectra adjustment based on the structural and luminescent properties investigations. Tb3+ ions enhance the fluorescence lifetime of Ce3+ ions from 61.1 to 63.8 ns and improve the luminescence efficiency, and the highest optical-optical conversion efficiency (OCE) is 270.56 lm/W. Corresponding luminescence shift from cold white to greenish yellow. Gd3+ ions increase the peak wavelength from 554 to 564 nm and improve the Ra value, and the maximum Ra is 75.5. Corresponding luminescence is shifted from cold white to reddish violet. In addition, the luminescence of Ce,Tb,Gd:YAG-Al 2 O 3 ECPPs is adjusted to warm white with CIE coordinate (0.374, 0.364) and CCT of 4102 K, and Ra of 73.0, which is of great significance for realizing the high-power warm white LED lighting. • Tb3+ ions increased the fluorescence lifetime of Ce3+ ions by ∼17%， and improved the luminescence efficiency with the highest OCE of 270.56 lm/W. And Gd3+ ions increased the peak wavelength of emission from 554 nm to 564 nm and improved the Ra from 65.5 to 75.5. • The Ce,Tb,Gd:YAG-Al 2 O 3 ECPP has excellent performance with a low CCT of ∼4100 K and a CIE coordinate of (0.374, 0.364). • The CRI of Ce,Tb,Gd:YAG-Al 2 O 3 ECPP reached 73.0. [ABSTRACT FROM AUTHOR]

Ho3+ and Eu3+ co-doping GdScO 3 crystal was successfully grown by special EFG method. The spectroscopic properties of the crystal were measured and analyzed. The absorption cross section was calculated to be 2.027 × 10−20 cm2 at 1161 nm. The J-O theory intensity parameters Ω t (t = 2, 4, 6), radiative transition rates, fluorescence branching ratios and radiative lifetimes were calculated. The Ho,Eu:GdScO 3 crystal has very strong emission at 2869 nm and the emission cross section was 13.524 × 10−21 cm2. The fluorescence lifetimes of the 5I 7 and 5I 6 levels were measured to be 4.457 ms and 1.265 ms. Confirmed that Eu3+ can be used as an effective deactivation ion of Ho3+ in GdScO 3 crystal. All those results show that the Ho,Eu:GdScO 3 crystal would be a potential laser material for ∼3 μm mid-infrared region. • Ho,Eu:GdScO 3 crystal was successfully grown. • The spectroscopic properties of the Ho,Eu:GdScO 3 crystal were analyzed. • J-O theory was applied to analyze fluorescence properties of the Ho,Eu:GdScO 3 crystal. • The energy transfer between Ho3+ and Eu3+ ions, spectroscopic characteristic of ∼3 μm emission were calculated and analyzed. [ABSTRACT FROM AUTHOR]

A series of 0.5 at.% Tm:Ca 1-x Y x F 2+x (x = 0, 0.01, 0.04, 0.06, 0.08, 0.12) crystals have been successfully grown by the temperature gradient technique (TGT) method. The absorption spectra, fluorescence spectra, and fluorescence decay curves were measured and analyzed at room temperature. By comparison, it is found that when the concentration of Y3+ ions reaches 8 at.%, the absorption cross section corresponding to the 3H 6 →3H 4 energy level is 2.56 × 10−21 cm2 at 793 nm, which is suitable for GaAlAs LD pumping. The J-O strength parameters Ω 2 , Ω 4 , and Ω 6 were obtained. With the incorporation of Y3+ ions, the value of Ω 4 /Ω 6 gradually increases. When the concentration of Y3+ ions reaches 8 at.%, the emission cross sections are 3.05 × 10−21 cm2 at 1476 nm, 2.56 × 10−21 cm2 at 2378 nm, and the full widths at half maximum (FWHM) are 76 nm and 195 nm, respectively. The fluorescence lifetime of 3H 4 level, the upper level of 1.5 μm and 2.3 μm, is 1.05 ms, which is very beneficial for 1.5 μm and 2.3 μm laser. • With the incorporation of Y3+ ions, the value of Ω 4 /Ω 6 gradually increases. • When the concentration of Y3+ ions reaches 8 at.%, the emission cross section is 3.05 × 10−21 cm2 at 1476 nm, 2.56 × 10−21 cm2 at 2378 nm, respectively. • The fluorescence lifetime of 3H 4 level, the upper level of 1.5 μm and 2.3 μm, is 1.05 ms, which is very beneficial for 1.5 μm and 2.3 μm laser. [ABSTRACT FROM AUTHOR]

Ho:Lu 2 O 3 crystal was successfully grown by TGT method. The spectroscopic properties of the crystal were analyzed. The absorption cross section of Ho:Lu 2 O 3 were 0.307 × 10−20 cm2 at 1147 nm and 1.076 × 10−20 cm2 at 1929 nm. J-O theory was applied to analyze fluorescence properties of the Ho:Lu 2 O 3 crystal. The intensity parameters Ω t (t = 2,4,6), radiative transition rates, branching ratios and radiative lifetime were calculated. The Ho:Lu 2 O 3 crystal had very strong emission at 2027 nm and 2849 nm and emission cross sections were calculated to be 3.271 × 10−21 cm2 and 8.852 × 10−21 cm2, respectively. The fluorescence lifetimes of the Ho3+5I 7 and 5I 6 levels were measured to be 12.400 ms and 0.622 ms. All those results show that the Ho: Lu 2 O 3 crystal would be a potential laser material for mid-infrared region. • Ho: Lu 2 O 3 crystal was successfully grown by TGT method. • The spectroscopic properties of the Ho: Lu 2 O 3 crystal were analyzed. • J-O theory was applied to analyze fluorescence properties of the Ho:Lu 2 O 3 crystal. • The gain cross-section of Ho:Lu 2 O 3 crystal for ∼2 μm region and ∼3 μm region were calculated. [ABSTRACT FROM AUTHOR]

Tm3+, Pr3+ co-doped Bi 4 Ge 3 O 12 (Tm,Pr:BGO) crystals with various Pr3+ doping concentration were successfully grown using the micro-pulling-down (μ-PD) method. The use of Pr3+ co-doping for deactivating the Tm3+ ions at 1.5 μm emission was investigated in the BGO single crystal for the first time. The effect of Pr3+ concentration on the spectroscopic properties of Tm,Pr:BGO crystals were demonstrated. In addition, the fluorescence lifetime of Tm3+:3F 4 level of 0.5 at.% Pr, 2 at.% Tm:BGO crystal was quenched effectively (from 5.64 ms down to 0.36 ms) and the population inversions between Tm3+:3H 4 and 3F 4 levels are enhanced to achieve a four-level laser system at 1.5 μm. • Tm,Pr:BGO crystals with different Pr3+ concentration were grown using by the micro-pulling-down method. • The effect of Pr3+ concentration on the spectroscopic properties of Tm,Pr:BGO crystals was studied. • The use of Pr3+ co-doping for deactivating the Tm3+ ions at 1.5 μm emission was investigated in BGO crystal. [ABSTRACT FROM AUTHOR]

• A series of 0.6 at% Pr:CaF 2 -RF 3 (R= Y3+, Gd3+, Lu3+) crystals were successfully grown by the temperature gradient technique(TGT) method. • By co-doping R3+ ion (R=Y3+, Gd3+, Lu3+), the spectral performance of the crystals could be significantly improved and the function effect is also different. • The spectral performance and spectral quality factor of the crystals were systematically described and compared for the first time. • The spectral modulation effect caused by Y3+, Gd3+ and Lu3+ co-doping ion was discussed. A series of 0.6 at% Pr:CaF 2 -RF 3 (R = Y3+, Gd3+, Lu3+) crystals have been successfully grown by the temperature gradient technique(TGT). The absorption spectra, fluorescence spectra, and fluorescence decay curves were measured and analyzed at room temperature. When the R3+ concentration is higher than a certain value, the diffraction peaks of Pr:CaF 2 -RF 3 crystals were well indexed to the (Ca,Y)F 2 phase. By co-doping R3+ ion (R=Y3+, Gd3+, Lu3+), the spectral performance of the crystals could be significantly improved and the function effect is also different. For 0.6 at% Pr, 28.5 at% Y:CaF 2 crystal, the fluorescence lifetime of 3P 0 energy level was fitted to be 45.46 µs, and the emission cross sections of 3P 0 →3H 6 (605 nm), and 3P 0 →3F 2 (641 nm) were calculated to be 1.78 × 10−20 cm2, and 4.61 × 10−20 cm2 with the full width at half (FWHM) of 20.1 nm and 6.8 nm, respectively. The 0.6 at% Pr, 28.5 at% Y:CaF 2 crystal could be favorble laser medium for ultra-fast laser opreration at 605 nm and 641 nm. For 0.6 at% Pr, 18 at% Gd:CaF 2 and 0.6 at% Pr, 10 at% Lu:CaF 2 crystals, the spectral quality factors σ em• τ f of 3P 0 →3F 2 transition (642 nm) were calculated to be 614.18 × 10−20 cm2•µs and 506.36 × 10−20 cm2•µs with the FWHM of 3.7 nm and 5.3 nm. All the results show that 0.6 at% Pr, 18 at% Gd:CaF 2 and 0.6 at% Pr, 10 at% Lu:CaF 2 crystals are promising gain media for high-efficiency visible laser output at 642 nm, which would compete with commercial Pr: YLF crystal in the future. [ABSTRACT FROM AUTHOR]

A Nd:BGSO crystal with the dimensions of Φ2 × 131 mm3 has been grown successfully by the micro-pulling-down method. The peak absorption cross-section at 808 nm was calculated to 0.98 × 10−20 cm2 with full-width at half-maximum of 17.4 nm. The stimulated emission cross-section was obtained to be 3.15 × 10−20 cm2 at 1063 nm. The fluorescence and radiative lifetimes of 4F 3/2 level were 248 μs and 300 μs respectively. All results indicate that the Nd: BGSO single crystal would be a promising near-IR solid-state laser material. [ABSTRACT FROM AUTHOR]

Ho3+-doped GdScO 3 crystal was successfully grown by the edge-defined film-fed growth (EFG) method. The spectroscopic properties of Ho:GdScO 3 crystal were investigated at room temperature. The peak absorption cross-sections were 0.33 × 10−20 cm2 and 1.24 × 10−20 cm2 at 1160 nm and 653 nm with full widths at half maximum of 171.7 nm and 11.5 nm. The peak emission cross-sections of 5I 7 →5I 8 and 5I 6 →5I 7 transitions for the crystal were 0.49 × 10−20 cm2 and 1.24 × 10−20 cm2, respectively. The fluorescence lifetimes of the 5I 6 and 5I 7 multiplets were measured to be 1.12 ms and 6.13 ms, respectively. The results show that Ho:GdScO 3 crystal is a very promising material for 3 μm laser operation. • Ho:GdScO 3 crystal was successfully grown by the edge-defined film-fed growth (EFG) method. • The structure parameters of Ho:GdScO 3 crystal were studied by X-ray diffraction (XRD). • Spectral properties and Judd-Ofelt parameters of Ho:GdScO 3 crystal were investigated and compared. [ABSTRACT FROM AUTHOR]

Tm3+-doped bismuth germanate crystals (Tm:BGO) with various doping concentrations of 0.5, 0.75, 1.0, 1.5, and 2.0 at.% were grown by the micro-pulling-down method (μ-PD). The effect of thulium concentration on the growth, structure, absorption spectra, emission spectra and fluorescence lifetime of 3H 4 and 3F 4 state was studied. Under excitation of 792 nm, Tm:BGO crystals exhibit two fluorescence bands corresponding to the 3H 4 → 3F 4 and the 3F 4 → 3H 6 transitions. The fluorescence lifetime of 3H 4 state decreased strongly as the thulium concentration increased, while the lifetime of 3F 4 state was relatively constant for all thulium concentrations. • Tm:BGO crystals with different Tm3+ concentration were grown by the micro-pulling-down method. • The effect of Tm3+ concentration on the growth, structure and spectroscopic properties of Tm:BGO crystals was studied. • Tm:BGO crystals exhibit two fluorescence bands corresponding to the 3H 4 → 3F 4 and the 3F 4 → 3H 6 transitions. [ABSTRACT FROM AUTHOR]

High-quality Dy:PbWO 4 crystal has been successfully grown by the Bridgman method. Fluorescence properties of the grown crystal at the yellow-light region were discussed. The absorption cross-section of Dy3+ ions at 454 nm was calculated to be 0.142 × 10−20 cm2, which corresponded to the transition from 6H 15/2 to 4I 15/2 level. Based on Judd-Ofelt theory, the J-O intensity parameters Ω t and the emission cross-section were calculated. The fluorescence lifetime of 4F 9/2 level was measured to be 193 μs. • Dy: PbWO 4 crystal was grown successfully by the Bridgman method. • Judd-Ofelt theory was used to analyze the spectral properties of Dy: PbWO 4 for the first time. • Dy: PbWO 4 crystal is a potential laser medium for yellow laser operation. [ABSTRACT FROM AUTHOR]