•Polarized spectra and thermal conductivity of the Dy3+:Lu2Si2O7 crystal have been measured.•Emission properties of 4F9/2 multiplet have been estimated based on the Judd-Ofelt theory.•The crystal has an emission peak and large emission cross-section at 589 nm.•The 4F9/2 → 6H13/2 transition is of prospect for a 589 nm laser channel.A trivalent dysprosium-doped Lu2Si2O7 single crystal was grown by the Czochralski method. Segregation coefficient of Dy3+ ion in the crystal is about 0.56. Spectroscopic properties of the crystal were investigated at room temperature. In particular, the polarized absorption spectra were analyzed using the Judd-Ofelt theory and the intensity parameters were determined. Then the spontaneous transition probabilities, branching ratios, and radiative lifetime related to the 4F9/2 multiplet were calculated. Emission cross-section for the 4F9/2 → 6H13/2 transition at 589 nm is up to 1.27 × 10−21 cm2 for E//Y polarization. Thermal conductivity of the crystal was measured to be 9.46 Wm−1K−1 at room temperature. The experimental results show that the Dy3+:Lu2Si2O7 crystal is a promising gain medium for solid state 589 nm laser.

A NaGd(MoO4)2 crystal doped with 2 at.% Sm3+ was grown by the Czochralski method. Polarized absorption and fluorescence spectra of the crystal were measured at room temperature. Spectroscopic parameters, including absorption and emission cross sections, Judd-Ofelt intensity parameters, radiative transition rates, fluorescence branching ratios, and fluorescence lifetime of the 4G5/2 multiplet, were obtained and compared with other Sm3+-doped crystals. The main fluorescence band around 646 nm is related to the 4G5/2→6H9/2 transition, which has a branching ratio of 45.4% and peak emission cross sections of 1.73×10–21 and 3.13×10–21 cm2 for π and σ polarizations, respectively. The results indicate that the Sm3+:NaGd(MoO4)2 crystal may be a potential gain medium of red visible laser pumped directly by commercially available 405 nm laser diode.

•An Yb3+:Gd2SiO5 single crystal was grown by the Czochralski method.•Polarized spectroscopic properties of Yb3+:Gd2SiO5 crystal were investigated.•Diode-pumped continuous-wave laser was demonstrated in Yb3+:Gd2SiO5 crystal.Yb3+:Gd2SiO5 single crystal with Yb3+ concentration of 6.33 at.% was grown by the Czochralski method. Polarized absorption and fluorescence spectra were measured at room temperature. Intrinsic fluorescence lifetime of the 2F5/2 multiplet was measured to be 0.87 ms when the powder of Yb3+:Gd2SiO5 crystal with low Yb3+ concentration of 0.5 at.% immersed in refractive index-matching fluid was adopted to weaken the influence of radiation trapping and concentration dependent fluorescence quenching. Furthermore, diode-pumped continuous-wave laser around 1090 nm with a slope efficiency of 52% and maximum output power of 1.2 W was demonstrated in the crystal.

•The polarized spectral properties of the Dy3+:NaGd(MoO4)2 crystal have been recorded.•The crystal takes on large branching ratio for yellow emission.•The emission cross-section of the crystal at 574 nm is much larger than that of Dy3+:LiNbO3.•The crystal shows the potential of direct yellow laser generation.A single crystal 1.85 at% Dy3+:NaGd(MoO4)2 was grown by the Czochralski method and spectroscopic properties of the crystal were investigated. Room temperature polarized absorption spectra were analyzed by the Judd–Ofelt theory. Then the intensity parameters, spontaneous transition probabilities, branching ratios, and radiative lifetimes of Dy3+ ions in the crystal were obtained. The peak polarized emission cross-sections for the 4F9/2 → 6H13/2 transition were calculated to be 1.62 × 10−20 and 1.35 × 10−20 cm2 for π and σ polarizations respectively by the Füchtbauer–Ladenburg equation. The fluorescence decay curve and quantum efficiency of the 4F9/2 multiplet were measured to be 156 μs and 74%, respectively. The experimental results show that the Dy3+:NaGd(MoO4)2 crystal can be pumped directly by commercially available 450 nm blue laser diodes and may be a promising yellow laser material.

Aluminate garnet phosphors Ca2GdZr2(AlO4)3:Ce3+ (CGZA:Ce3+) for solid-state white lighting sources are reported. The crystal structure and Mulliken bonding population of the CGZA:Ce3+ have been analyzed. The larger 5d (2D) barycenter shift εc and smaller phenomenological parameter 10Dq of Ce3+ in CGZA are related to the larger covalent character of Ce–O. The tuning spectral properties of the Ce3+-doped CGZA-based isostructural phosphors are presented. The splitting of cubic crystal field energy level 2Eg in Ca2REZr2(AlO4)3:Ce3+ (CREZA:Ce3+) (RE = Lu, Y, and Gd) increases as the radius of RE3+ increases, and the splitting of 2Eg may dominate the difference of spectroscopic red-shift D(A) in CREZA:Ce3+. The splitting of the 2Eg in CaGd2ZrSc(AlO4)3:Ce3+ (CGZSA:Ce3+) phosphors increases seemly due to the decreasing of the covalent character of Ce–O. Thermal quenching properties of Ce3+-doped CGZA-based isostructural phosphors are also presented and analyzed. For CREZA:Ce3+ phosphors, the increasing of the radius of RE3+ results in an enhancement of thermal quenching. The quenching of CGZSA:Ce3+ is obviously stronger mainly due to the smaller energy difference between the lowest 5d excited state and 4f ground state.

•Polarized spectral properties of Sm3+:LiYF4 crystal at room temperature were analyzed in detail.•The emission cross sections for the transitions of special interest for visible laser application are calculated.•Sm3+:LiYF4 is a promising laser material for 401 nm GaN LD pumped 605 nm visible laser.A trivalent samarium-doped LiYF4 single crystal was grown by the vertical Bridgman technique. Its polarized absorption and fluorescence spectra and fluorescence decay curves were recorded at room temperature. On the basis of the Judd–Ofelt theory, the spectral parameters of the Sm3+:LiYF4 crystal were calculated. The emission cross sections for the 4G5/2→6HJ(J=5/2, 7/2. 9/2, and 11/2) transitions of special interest for visible laser application were obtained by the Fuchtbauer–Ladenburg formula.

•A series of phosphors Li3Ba2La3(WO4)8:Dy3+ with different Dy3+ concentrations were synthesized via the solid-state reaction.•Photoluminescence properties of the Li3Ba2La3(WO4)8:Dy3+ phosphors are investigated in detail.•The Li3Ba2La3(WO4)8:0.6Dy3+ phosphor with strong yellow emission may be applied in near ultraviolet pumped white LEDs.Li3Ba2La3(WO4)8:Dy3+ yellow-emitting phosphors were synthesized by the solid state reaction method. These phosphors exhibit one intense emission band around 575 nm under excitation at 365 nm. The dependences of the emission intensities and the chromaticity coordinates on Dy3+ concentration were analyzed. The optimum doping concentration of Dy3+ for the phosphor is about 6 mol% and the corresponding chromaticity coordinates is (0.435, 0.476) at room temperature. Besides, the Li3Ba2La3(WO4)8:Dy3+ phosphor shows higher thermal stability than that of (Sr, Ba)2SiO4:Eu2+. The results show that the Li3Ba2La3(WO4)8:Dy3+ phosphor with strong yellow emission may be applied in near ultraviolet pumped white LEDs.

•Polarized spectral properties of Sm3+:LiLuF4 at room temperature were analyzed.•Emission cross sections for the transitions of special interest for visible laser application were calculated.•Sm3+:LiLuF4 is a promising laser material at 605 nm pumped by 401 nm LD.A Sm3+-doped LiLuF4 single crystal was grown by the vertical Bridgman–Stockbarge technique. Polarized absorption spectra, polarized fluorescence spectra, and fluorescence lifetime of the Sm3+:LiLuF4 crystal were recorded at room temperature. Based on the Judd–Ofelt theory, spectral parameters of the Sm3+:LiLuF4 crystal were calculated. Emission cross sections for the 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions with special interest for visible laser application were obtained by the Füchtbauer–Ladenburg formula. The results indicate that the Sm3+:LiLuF4 crystal may be a potential laser gain medium operating in visible region pumped by diode lasers around 401 nm.

•Dy3+ and Tm3+ single and co-doped tungsten borate glasses have been synthesized.•Color tunable can be achieved in Dy3+ single-doped and Dy3+/Tm3+ co-doped glasses.•The glass is potentially applicable as white light emitting diodes.RE3+ (RE3+ = Tm3+, Dy3+) ion single and co-doped tungsten borate glasses for white light emitting diodes (LEDs) were prepared by melt quenching method. Emission and excitation spectra of the glasses were measured. The color of luminescence can be tuned by changing the composition of glass matrix or the concentrations of Tm3+ and Dy3+ ions. White light emission can be achieved from 0.5Dy3+ single-doped 15WO3–25La2O3–60B2O3 and 0.4Tm3+/1.5Dy3+ co-doped 50WO3–25La2O3–25B2O3 glasses. In addition, energy transfers between Tm3+ and Dy3+ were also analyzed. The Dy3+/Tm3+ co-doped tungsten borate glasses may be potential candidates for white LED application.

The polarized absorption and photoluminescence were investigated in a Tm3+-doped β′-Gd2(MoO4)3 single crystal. The spectroscopic parameters were calculated based on the Judd–Ofelt theory. Fluorescence emissions and decay curves were measured under different excitations. Results have indicated that the Tm3+:β′-Gd2(MoO4)3 crystal has good application prospects both in blue phosphor for white LED and in eye-safety lasing around 1.9 μm.Highlights► Spectroscopy and photoluminescence of Tm3+:GM crystal are investigated. ► The spectroscopic parameters are calculated based on the J–O theory. ► The Tm3+:GM crystal has very good fluorescence properties in the blue and 1.9 μm region. ► Results are useful for exploiting phosphor of white LED and eye-safety high performance laser.

•Polarized spectral properties of Ho3+/Tm3+:β′-Gd2(MoO4)3 crystal were studied.•Broad absorption band of the crystal around 795 nm is suitable for LD pumping.•Peak emission cross section around 2.0 μm is comparable to that of Ho3+:YAG.•Coupling decay behavior of Tm3+ and Ho3+ embodies energy transfer between them.•Ho3+ laser around 2.0 μm with a tunable range of about 130 nm can be expected.Ho3+/Tm3+ co-doped β′-Gd2(MoO4)3 single crystal was investigated as gain medium for Ho3+ laser around 2.0 μm. Polarized absorption and fluorescence spectra of the crystal were measured. Polarized spectral parameters of Ho3+ ions in the crystal were calculated and the gain curves around 2.0 μm were estimated. The fluorescence decay curves for Tm3+ and Ho3+ ions related to the 2.0 μm laser were measured and analyzed. The distinct coupled decay behavior for the Ho3+/Tm3+ co-doped system embodies the existence of energy transfer between Tm3+ and Ho3+ ions.

A Nd3 +-doped transparent oxyfluoride glass ceramic containing Sr5(PO4)3F nanocrystals was prepared by melt quenching technique and subsequent thermal treatment. The phase and morphology of Sr5(PO4)3F nanocrystals were investigated by X-ray diffraction and transmission electron microscopy, respectively. The volume fraction of Sr5(PO4)3F nanocrystals in the glass ceramic is about 12% and the fraction of Nd3 + ions incorporated in the Sr5(PO4)3F nanocrystals is about 15%. The peak absorption cross-section increases to 145% at 806 nm and the full width at half maximum for the band around 806 nm decreases from 12.5 to 11 nm after the crystallization process. The 1059 nm peak stimulated emission cross-section increases from 2.27 × 10− 20 to 3.07 × 10− 20 cm2 and the effective width for this band decreases from 35 to 30 nm after the crystallization process. The improvement of spectroscopic properties indicates that the glass ceramic is potentially applicable as a 1.06 μm laser material.Highlights► Nd3 +-doped transparent glass ceramic containing Sr5(PO4)3F nanocrystals has been synthesized. ► The spectroscopic properties of Nd3 + ions in the Sr5(PO4)3F nanocrystals have been investigated. ► The glass ceramic is potentially applicable as the 1.06 μm laser material.

Efficient monolithic 1.9 μm micro-laser was realized in a 1.1-mm-thick, 6.4 at.% Tm3+:BaGd2(MoO4)4 unprocessed cleaved plate coated with the cavity mirrors directly. End-pumped by a fiber-coupled 795 nm diode laser, continuous-wave output power of 250 mW was obtained when incident pump power was 1.15 W. Slope efficiencies with respect to incident and absorbed pump power were 36% and 61%, respectively. End-pumped by a single-stripe 805 nm diode laser, which is more favorable for constructing a compact and inexpensive 1.9 μm all-solid-state laser, continuous-wave output power of 100 mW was obtained when incident pump power was 2.0 W. Slope efficiencies with respect to incident and absorbed pump power were 11% and 23%, respectively. The spectra and spatial profiles of the monolithic Tm3+:BGM micro-laser were also measured and analyzed.Highlights► A monolithic micro-laser was realized from an Tm3+:BaGd2(MoO4)4 cleaved plate. ► Cavity mirrors were deposited onto the faces of the unprocessed cleaved plate. ► An efficient 1.9 μm laser was demonstrated under diode laser pumping. ► CW output power of 250 mW was obtained when incident pump power was 1.15 W. ► Slope efficiency with respect to absorbed pump power was 61%.

•An Er3+-doped Sr3Yb2(BO3)4 crystal was grown by the Czochralski method.•Polarized spectral properties of the Er:Sr3Yb2(BO3)4 crystal were investigated.•Quasi-CW 1.55 μm laser of 0.75 W was obtained in the crystal.•1.55 μm Er3+ laser in a ytterbium stoichiometric crystal was first realized.Undoped and Er3+-doped Sr3Yb2(BO3)4 crystals were grown by the Czochralski method. Room temperature polarized spectral properties of the Er:Sr3Yb2(BO3)4 crystal were investigated. The efficiency of the energy transfer from Yb3+ to Er3+ ions in this crystal was calculated to be about 95%. End-pumped by a diode laser at 970 nm in a hemispherical cavity, a 0.75 W quasi-CW laser at 1.5–1.6 μm with a slope efficiency of 7% and an absorbed pump threshold of 3.8 W was achieved in a 0.5-mm-thick Z-cut crystal glued on a 5-mm-thick pure YAG crystal with UV-curable adhesive.

A pure and a Tm3+-doped Li3Ba2La3(WO4)8 single crystal were grown by the top seeded solution growth method from Li2WO4 flux. The structure of the pure crystal was determined by the single-crystal X-ray diffraction method. It crystallizes in the monoclinic space group C2/c with a = 5.323(6) (Å), b = 13.091(15) (Å), c = 19.48(2) (Å), β = 91.18(3)°, and Z = 2. In the structure, La3+ and Li+ share the same 8f lattice site with a ratio of occupancy of 0.75:0.25. The high structural disorder of the Li3Ba2La3(WO4)8 crystal leads to inhomogeneous spectral broadening of Tm3+ ions contained within it, for which the absorption bands around 795 nm are broad and emission bands around 1.9 μm are smooth. Pumped by a quasi-continuous-wave diode laser at 795 nm, an output power of 3.0 W with slope efficiency of 40% around 1.9 μm was achieved in a Tm3+:Li3Ba2La3(WO4)8 crystal. The results indicate that the Tm3+:Li3Ba2La3(WO4)8 crystal is a promising gain medium for a tunable laser around 1.9 μm.

An Er3+:BaGd2(MoO4)4 single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves were measured. In the framework of Judd–Ofelt theory, intensity parameters, spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes were calculated. Besides, green upconversion fluorescence was also observed.Highlights► An Er3+:BaGd2(MoO4)4 single crystal was grown by the Czochralski technique. ► The polarized spectroscopic properties of Er3+:BaGd2(MoO4)4 crystal were studied. ► The crystal exhibits large emission cross section and broad bandwidth around 1.55 μm. ► The results reveal that Er3+:BaGd2(MoO4)4 crystal is a potential laser material.

A Nd3 +-doped transparent oxyfluoride glass ceramic containing Ca5(PO4)3F nanocrystals was prepared by thermal treatment at the crystallization temperature for the precursor glass. The transmittances of the precursor glass and the glass ceramic with a thickness of about 2 mm are up to 84.7% and 77.4% in the visible range. The volume fraction of Ca5(PO4)3F nanocrystals in the glass ceramic is about 19% and the ingress fraction of Nd3 + ions into the Ca5(PO4)3F nanocrystals is about 32%. The peak absorption cross-section increases to 224% at 807 nm and the full width at half maximum for the 807 nm band decreases from 17.5 to 3.5 nm after the crystallization process. The peak stimulated emission cross-section increases from 1.89 × 10− 20 to 2.42 × 10− 20 cm2 at 1062 nm and the effective width of the emission line for the 1062 nm band decreases from 34 to 29 nm after the crystallization process. The improvement of spectroscopic properties indicates that the glass ceramic is potentially applicable as the 1.06 μm laser material.Highlights► Existence of Nd:Ca5(PO4)3F nanocrystals was demonstrated by low temperature spectra. ► Nd3 + concentration in Ca5(PO4)3F nanocrystals was estimated from absorption spectra. ► The glass ceramic is potentially applicable as the 1.06 μm laser material.

Efficient eye-safe 1.6 μm monolithic laser was realized in a c-cut, 0.7-mm-thick Er3+:Yb3+:YAl3(BO3)4 microchip end-pumped by a quasi-continuous-wave 970 nm diode laser. At incident pump peak power of 20.4 W, a maximum output peak power of 2.6 W with a slope efficiency of 19% was obtained when the waist radius of pump laser beam was 220 μm. The spectra and profiles of output beam of the Er3+:Yb3+:YAl3(BO3)4 monolithic laser were measured. The influences of the waist radius of pump laser beam on the slope efficiency and threshold of the monolithic laser were also investigated.

Trivalent thulium-doped K5Bi(MoO4)4 single crystals were grown by the Czochralski method. Its polarized absorption and fluorescence spectra and fluorescence decay curves were recorded at room temperature. On the basis of the Judd–Ofelt theory, the spectral parameters of the Tm3+:K5Bi(MoO4)4 crystal were calculated. The cross relaxations between Tm3+ ions were analyzed. The emission cross sections of the 3F4 → 3H6 transition were obtained by the Fuchtbauer–Ladenburg formula and then the gain cross sections around 1.9 μm were calculated. The peak emission cross section and width of emission band around 1.9 μm are comparable to those for Tm3+:YAG and the tunable range is about 280 nm for the potential ∼1.9 μm laser operation via the 3F4 → 3H6 transition.Highlights► Detailed spectral properties of Tm3+-doped K5Bi(MoO4)4 were analyzed. ► The peak emission cross section around 1.9 μm is comparable to that of Tm3+:YAG. ► About 280 nm tunable range of the potential ∼1.9 μm laser operation can be expected for the Tm3+:K5Bi(MoO4)4 crystal.

A Ho3+-doped NaLa(MoO4)2 single crystal was grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The spontaneous emission probabilities, radiative lifetimes, and fluorescence branching ratios of the typical fluorescence multiplets of Ho3+ ions were calculated. The polarized stimulated emission and gain cross-sections of the 5I7 → 5I8 transition were obtained. The results show that the Ho3+:NaLa(MoO4)2 crystal is a promising gain medium for tunable and ultrashort pulse lasers operating around 2.0 μm.Research highlights► A Ho3+-doped NaLa(MoO4)2 single crystal was grown by the Czochralski method. ► Polarized spectroscopic properties of the crystal are reported. ► The crystal is a promising gain medium for 2.0 μm laser with large tunable range.

Nd3+-doped bismuth borate glasses were synthesized by the conventional melt-quenching method and the spectroscopic properties related to the operation of 1.06 μm laser were investigated. Efficient quasi-continuous-wave laser oscillations around 1065 nm were demonstrated in the glasses. In a hemispherical cavity end-pumped by a Ti:sapphire laser, a maximum output peak power of 185 mW with slope efficiency of 25% was achieved in a 3.1-mm-thick 0.5Nd2O3·99.5(4Bi2O3·6B2O3) glass, and the absorbed pump threshold was about 70 mW. Furthermore, laser oscillation was achieved in a range from 1058 to 1075 nm, which shows that tunable and ultra-short pulse lasers may be realized in the glasses.

Bismuth borate glasses doped with a series of Tm3+ concentrations were successfully prepared by the melt-quenching technique. Their absorption spectra, fluorescence spectra, and fluorescence decay curves were recorded at room temperature. On the basis of the Judd–Ofelt theory, the intensity parameters and other spectral parameters related to the luminescent performance were obtained. Especially, the fluorescence concentration quenching of the 1G4 multiplet and the related mechanisms were analyzed detailedly. Consequently, an approach to investigate the fluorescence concentration quenching in Tm3+-doped materials is proposed.

A Pr3+-doped KY(MoO4)2 single crystal was grown by the Czochralski method. The polarized absorption and fluorescence spectra of the Pr3+:KY(MoO4)2 crystal were measured at room temperature. The stimulated emission cross-sections for the transitions from the 3P0 multiplet were estimated from the fluorescence spectra. The fluorescence lifetime of the 3P0 multiplet was estimated from the fluorescence decay curve at room temperature. The analysis of spectral properties shows that the Pr3+:KY(MoO4)2 crystal is a promising gain medium for visible lasers.

The polarized absorption spectra, infrared fluorescence spectra, upconversion visible fluorescence spectra, and fluorescence decay curve of orientated Nd3+:KGd(WO4)2 crystal were measured at room-temperature. Some important spectroscopic parameters were investigated in detail in the framework of the Judd–Ofelt theory and the Fuchtbauer–Ladenburg formula. The effect of the crystal structure on the spectroscopic properties of the Nd3+ ions was analyzed. The relation among the spectroscopic parameters and the laser performances of the Nd3+:KGd(WO4)2 crystal was discussed.

A high optical quality Er3+-doped NaGd(WO4)2 single crystal with dimensions of ∅18 × 50 mm3 has been grown using the Czochralski method. The structure of the grown crystal was proved by X-ray powder diffraction. The accurate concentration of Er3+ ion in the crystal was measured. The absorption spectra, fluorescence spectra and fluorescence lifetime of the crystal were measured at room temperature. Green up-conversion luminescence has been observed when the crystal is excited at 965 nm.

Er3+-doped YAl3(BO3)4 (YAB) crystal has been grown by the top-seeded solution method. The Judd–Ofelt (J–O) theory has been applied to analyze the polarized absorption spectra of Er3+ ions in the uniaxial crystal measured at room temperature, and the effective J–O parameters have been determined as: Ω2 = 8.38 × 10−20 cm2, Ω4 = 1.61 × 10−20 cm2, Ω6 = 1.50 × 10−20 cm2. The parameters have been used to calculate the spontaneous emission probability and radiative lifetime of 4I13/2 manifold for the Er3+ ions. The fluorescence lifetime of this manifold has been measured and the quantum efficiency has been estimated. The emission cross-sections for the 4I13/2 → 4I15/2 transition calculated using the Fuchtbauer–Ladenburg and the reciprocity methods are compared.

Er3+-doped Li6Y(BO3)3 single crystal with dimensions of ϕ20 × 40 mm3 has been grown by the Czochralski method and the accurate concentration of Er3+ ions in the crystal was measured. The structure of the grown crystal was proved by X-ray powder diffraction and its hygroscopic behavior was also studied. The absorption spectrum, fluorescence spectrum, and decay curve of the crystal were measured at room temperature. The spectroscopic parameters of the crystal were compared with those of other Er3+-doped crystals.

Visible quantum cutting has been observed in Pr3+-doped PbWO4 crystal under ultraviolet excitation. Quantum cutting in this crystal consists of the 1S0 → 1D2 (around 325 nm) and 1D2 → 3H4 transitions (around 604 nm). Energy transfers between the host and Pr3+ ions can convert the ultraviolet emission from the 1S0 → 1D2 transition into a visible emission from the 3PJ (J = 0, 1) and 1D2 multiplets in the range of 490–650 nm. This work provides a potential approach for the development of high efficient visible quantum cutting phosphors and scintillators.Quantum cutting observed in Pr3+:PbWO4 crystal consists of the 1S0 → 1D2 and 1D2 → 3H4 transitions. Energy transfers between the host and Pr3+ ions can convert the ultraviolet emission from 1S0 → 1D2 into a visible emission. This work provides a potential approach for the development of high efficient visible quantum cutting phosphors and scintillators.

Top seeded solution growth of ytterbium-doped gadolinium aluminium borate (Yb3+:GAB) crystals with different Yb3+ concentration (x = 0.125, 0.33, 0.509, and 0.74) is reported. The polarized absorption spectra, emission spectra, and fluorescence lifetime of 50.9 at.% Yb3+-doped GAB crystal were measured at room temperature. The X-ray powder diffraction proved that the structure of the 50.9 at.% Yb3+:GAB crystal is the same as the pure GAB crystal with space group R32. The spectroscopic parameters of the crystal were compared with those of low Yb3+-doped GAB crystal. The results show that the Yb3+:GAB crystals with high Yb3+ concentration are potential candidates for compact and efficient microchip laser media.

Yb3+-doped La2(WO4)3 single crystals were grown by the Czochralski technique. Absorption and fluorescence spectra of the crystal were recorded at the room temperature. The stimulated emission cross-sections of Yb3+ ions were calculated using the reciprocity method and Fuchtbauer–Ladenburg formula, respectively. The fluorescence decay curves of 2F5/2 manifold of Yb3+ ions were recorded at room temperature for both crystal and powder samples. The effect of radiation trapping on the spectroscopic properties is discussed. Comparison with other Yb3+-doped laser crystals is made. The results show that Yb3+:La2(WO4)3 crystal is a promising laser material.

Based on a quasi-three-level system, a theoretical model of end pumped fundamental continuous wave (CW) Yb3+:YAl3(BO3)4 (Yb3+:YAB) microchip laser is proposed. The fluorescence concentration quenching effect, temperature distribution in the gain medium, and the absorption of the host have been taken into account in the model. A comparison between the calculated results and those of experiments reveals that this model is reasonable to some extent and applicable not only to the Yb3+:YAB microchip laser, but also to other quasi-three-level microchip lasers.