•A Dy-doped LaF3 sing crystal was successfully grown by the Bridgman method.•The spectral parameters of Dy:LaF3 crystal were calculated in detail.•Optical properties of Dy:LaF3 for ∼2.86 μm and 570 nm lasers were systematically studied for the first time.A Dy:LaF3 crystal was grown successfully by the Bridgman method, and X-ray diffraction results show that it is well-crystallized. The room temperature absorption spectra, fluorescence spectra and the fluorescence decay curves were measured. On the basis of J-O theory, the emission probabilities, branching ratios, and the radiation lifetimes of the 4F9/2 and 6H13/2 manifolds were calculated. The stimulated emission cross-sections of the 4F9/2 → 6H13/2 transition (∼570 nm) and the 6H13/2 → 6H15/2 transition (∼2.86 μm) were obtained by the Fuchtbauer–Ladenburg equation. The fluorescence lifetime of the 4F9/2 and 6H13/2 manifolds are 1.37 ms and 9.73 ms, respectively. All these results were first investigated, indicating the Dy:LaF3 crystal a promising material for 570 nm and 2.86 μm laser applications.

•Cr,Fe:ZnSe polycrystalline was first prepared by controlled thermal diffusion method.•The spectroscopic characterization and energy transfer mechanism of Cr,Fe:ZnSe were reported.•The transfer rate is much faster than the photoluminescence decay.•Laser operation at 3.7–4.5 μm via Cr2+ → Fe2+ energy transfer is feasible.The spectroscopic characterization and energy transfer mechanism of iron-chromium co-doped ZnSe polycrystalline (Cr,Fe:ZnSe) were reported with dimension of 15 mm × 15 mm × 2 mm obtained by controlled post-growth thermal diffusion method. The infrared absorption is characterized by a strong broad-band centered at 1770 nm which can be attributed to the only spin-allowed transition 5T2 → 5E within the 3d4 shell of Cr2+ ions. Photoluminescence spectrum shows a relatively strong broad emission band centered at 4.1 μm with a width of 0.8 μm (FWHM) under 1770 nm excitation at room temperature and reveals effective Cr2+ → Fe2+ energy transfer process. Room temperature photoluminescence decay about 8 μs was measured. All the results indicate that Cr,Fe:ZnSe could achieve laser operation at 3.7–4.5 μm via Cr2+ → Fe2+ energy transfer using a more convenient laser pump source in the near IR region.

•Cw dual-wavelength laser of Nd:LaF3 at 1040 nm and ∼1065 nm was detailed demonstrated for the first time.•A maximum output power of 302 mW was obtained with a slope efficiency of 18.5% with respect to the pump power.•Thermal conductivity of Nd:LaF3 crystal was detailed studied in the range of 300–575 K for the first time.A Nd-doped LaF3 crystal was grown by Czochralski method, and the rocking curves of (0 0 2) and (1 1 0) diffraction planes show good crystallinity quality of the as-grown crystal. Room-temperature fluorescence spectrum and transmittance spectrum of Nd:LaF3 crystal were investigated, both indicating probable dual-wavelength emissions at ∼1.04 μm and ∼1.06 μm. The thermal diffusivity and thermal conductivity of Nd:LaF3 crystal were detailed studied. Cw dual-wavelength laser operation of Nd:LaF3 single crystal at 1040 nm and around 1065 nm with LD pumping was demonstrated. A maximum output power of 302 mW was obtained with a slope efficiency of about 18.5% with respect to the pump power. The results of our study indicate the Nd:LaF3 crystal a promising laser crystal.

Large-scale titanium-doped sapphire (Ti:sapphire) crystal was grown in a 380 mm diameter molybdenum crucible using the heat exchange method (HEM) and characterized. The diameter of the core Ti:sapphire single crystal was estimated to be slightly larger than 200 mm. A Ti:sapphire crystal wafer 157 mm in diameter and 28 mm thick was obtained. Characterization based on X-ray diffraction spectroscopy, Raman spectroscopy, and absorption and fluorescence spectroscopy was carried out. The as-grown Ti:sapphire crystal had high intrinsic quality and a large figure of merit (FOM) without additional annealing. The high optical quality of the as-grown Ti:sapphire crystal indicated it is suitable for ultra-fast ultra-high-power lasers in chirped pulse amplification systems.

•Ho:PbF2 crystal was successfully prepared.•The spectral parameters of Ho:PbF2 crystal were calculated in detail.•Optical properties of Ho:PbF2 for 2 μm laser were studied for the first time.A Ho:PbF2 crystal was grown successfully by the conventional technique modified Bridgman method. Based on the Judd–Ofelt theory, the spectral parameters of Ho3+ were studied in detail by using the absorption spectrum of the as-grown crystal. Moreover, the emission probabilities, branching ratio, and radiative lifetime for the as grown crystal were also calculated. The stimulated emission cross-sections of the 5I7 → 5I8 transition were calculated by using the Fuchtbauer–Ladenburg (FL) method. The fluorescence lifetime of the 5I7 manifold was measured with a value of 13.6 ms. We propose that the Ho:PbF2 crystal may be a promising material for 2 μm laser applications.

•The growth and properties of Tb3−xNdxGa5O12 crystal were first reported.•The Verdet constant is larger than that of Tb3Ga5O12 crystal.•The extinction ratio is larger than that of Tb3Ga5O12 crystal.•The Nd3+ and Tb3+ super-exchange interaction may enhance the Verdet constant.Tb3−xNdxGa5O12 single crystal with dimension of Φ22 mm × 28 mm and a good optical quality was grown by the Czochralski method. X-ray powder diffraction was carried out and lattice parameters were calculated, which showed that the single crystal belongs to cubic crystal system. The transmission spectrum in the wavelength range of 450–1500 nm, which indicated the crystal has low absorption coefficient at 900–1450 nm. The Verdet constants of Tb3−xNdxGa5O12 at 532, 633 and 1064 nm wavelengths calculated by the extinction method are 225, 145 and 41 radm−1 T−1, respectively, which are larger than that of commercial TGG (Tb3Ga5O12) reported. The magneto-optical figures of merit of the crystal calculated is 3162°/dB at 1064 nm, and the extinction ratio is larger than that of commercial TGG.

•Highly transparent terbium gallium garnet (Tb3Ga5O12; TGG) single crystal was grown by the FZ method for the first time.•TGG exhibits superior optical and magneto-optical properties grown by FZ method.•The low cost and short growth of FZ method can effectively meet the increasing demand of VI–IR Faraday rotators.Highly transparent terbium gallium garnet (Tb3Ga5O12; TGG) single crystal having a large Verdet constant based on the visible and near-infrared region (VIS–NIR) Faraday rotator was grown by Floating Zone (FZ) growth machine. We successfully grew TGG single-crystal rods of 8–10 mm in diameter, which was suitable for the use in optical devices. The crystal showed a full-width at half-maximum as little as 18 arcsec by the X-ray rocking curve measurement. The Faraday rotation (B = 0.55T) was investigated at wavelength of 532, 632.8, 1064 nm at room temperature. The lower weak absorption coefficient, higher Verdet constant, thermal conductivity and laser induced damage threshold (LIDT) compared to the commercial TGG gives the great potential of using this new method to meet the increasing demand of VIS–NIR Faraday rotators (FRs).

The performances of continuous-wave (CW) and Q-switched Tm/Mg:LiTaO3 lasers were demonstrated in this paper. A maximum CW output power of 1.1 W at 1927.4 nm was achieved under output coupler (OC) of TOC=1.0% with a slope efficiency of 10.1%. Employing a single-layer graphene (SLG) as saturable absorber, pulses as short as 845 ns were obtained at a central wavelength of 1907.5 nm under a repetition frequency of 46.6 kHz, resulting in a single pulse energy of 20.0 μJ and peak power of 23.6 W.

A new red-emitting phosphor Ca9Lu(PO4)7:Ce3+, Mn2+ has been synthesized by solid-state reaction, and its luminescence properties have been investigated. The broad red emission peaked at 645 nm of Mn2+ is greatly enhanced by the sensitizer Ce3+ due to efficient energy transfer from Ce3+ to Mn2+. The energy transfer was demonstrated to belong to a resonant type via a dipole–quadrupole mechanism. The critical distance for Ce3+→Mn2+ energy transfer was calculated to be 15.04 Å by concentration quenching method. Preliminary results indicate that the phosphor might be a promising red phosphor for UV-based white LEDs.Highlights► We found a promising red-emitting phosphor Ca9Lu(PO4)7:Ce3+, Mn2+. ► It shows a broad emission band from 580 nm to 720 nm. ► The energy transfer mechanism from the Ce3+ to Mn2+ ions is a dipole-quadrupole interaction.

Polarized spectroscopic properties of a Ho3+-doped LuLiF4 (Ho:LuLF) single crystal grown by the Czochralski method have been investigated as a promising material for 2 μm and 2.9 μm lasers. The Judd–Ofelt (J–O) model has been applied to the analysis of the polarized room temperature absorption spectra to establish the so-called J–O intensity parameters. Based on the calculated parameters, we determined the emission probabilities, branching ratio and radiative lifetime for the Ho3+ transitions from the excited state manifolds to the lower-lying manifolds. Ho:LuLF crystal shows long fluorescence lifetime of 5I7 manifold (16 ms) and broad absorption and emission spectra, which exhibit strong polarization characteristics. Stimulated emission cross-sections spectra of the 5I6 → 5I7 and 5I7 → 5I8 transitions were derived and compared with those of the other well-known Ho3+-doped laser crystals.Highlights► A 1at.% Ho3+-doped LiLuF4 single crystal with high optical quality was successfully grown by Czochralski method. ► Polarized spectroscopic properties of this crystal were investigated systematically. ► The emission properties of the 5I6 → 5I7 transition of this crystal were studied for the first time to our knowledge.

Comparative study of the optical properties of undoped and 1–3 mol% MgO doped near-stoichiometric LiTaO3 (SLT) crystals were undertaken. It was observed that the red shift in the absorption edge occurred with the increasing MgO doping concentration. The infrared absorption spectrum of the OH-stretch-mode in SLT was measured for crystals of undoped and 1–3 mol% MgO doped compositions. The coercive field for the crystals was measured to be 0.913, 0.610 and 0.735 kV/mm for 1–3 mol% MgO doped SLT, respectively. Photorefractive damage of SLT single crystals with 1–3 mol% MgO doping levels was measured to be 136.29, 180.25 and 222.54 MW/cm2.Highlights► MgO-doped SLT crystals were grown by the Czochralski (Cz) method. ► The red shift in absorption edge and OH-stretch-mode occurred in MgO-doped SLT crystals. ► Mg2+ ions doped decrease the coercive field and increase the photorefractive damage.

A series of red-emitting phosphors Eu3+-doped M2Gd4(MoO4)7 (M=Li, Na) have been successfully synthesized at 850 °C by solid state reaction. The excitation spectra of the two phosphors reveal two strong excitation bands at 396 nm and 466 nm, respectively, which match well with the two popular emissions from near-UV and blue light-emitting diode chips. The intensity of the emission from 5D0 to 7F2 of M2(Gd1−xEux)4(MoO4)7 phosphors with the optimal compositions of x=0.85 for Li or x=0.70 for Na is about five times higher than that of Y2O3:Eu3+. The quantum efficiencies of the entitled phosphors excited under 396 nm and 466 nm are also investigated and compared with commercial phosphors Sr2Si5N8:Eu2+ and Y3A5O12:Ce3+. The experimental results indicate that the Eu3+-doped M2Gd4(MoO4)7 (M=Li, Na) phosphors are promising red-emitting phosphors pumped by near-UV and blue light.Graphical AbstractThe intensity of the red emission of M2(Gd1−xEux)4(MoO4)7 (M=Li, Na) phosphors with the optimal compositions is about five times higher than that of Y2O3:Eu3+.Highlights► Two novel Eu3+-doped red phosphors (Na2Gd4(MoO4)2, Li2Gd4(MoO4)7) were synthesized. ► Their emission intensities are about five times higher than that of Y2O3:Eu3+. ► Their quantum efficiencies are higher than that of commercial red phosphor Sr2Si5N8:Eu2+.

•Ho/Yb:PbF2 crystal was successfully grown.•The spectral parameters of Ho/Yb:PbF2 crystal were calculated in detail for the first time.•Optical properties of Ho/Yb:PbF2 as 2 μm laser crystal were evaluated.Single crystal of Ho3+/Yb3+ co-doped PbF2 has been grown successfully by the conventional technique modified Bridgman method. The spectral parameters of Ho3+ were calculated based on the Judd-Ofelt theory. The transition probabilities, radiative lifetime, and branching ratios were also estimated in detail by the J-O parameters obtained. The 2 μm emission characteristic and fluorescence lifetime of the 5I7 manifold upon excitation of a conventional 970 nm laser diode were measured and investigated. Fuchtbauer-Ladenburg theory was applied to calculate the absorption, emission, and gain cross sections of 5I7→5I8 transition. Based on examination of spectroscopic parameters evaluated, we suggest Ho3+/Yb3+ co-doped PbF2 crystal is a promising candidate for efficient 2 μm laser.

•A Tm-doped LaF3 sing crystal was successfully grown from the melt.•The spectral parameters of Tm:LaF3 crystal were calculated in detail.•Optical properties of Tm:LaF3 for ∼1.84 μm lasers were systematically studied for the first time.Optical properties of a Tm-doped LaF3 single crystal have been detailed investigated as a promising material for ∼1.84 μm lasers for the first time. Judd-Ofelt theory was applied to analyze the absorption spectrum. With the J-O intensity parameters Ωt(t=2,4,6), the emission probabilities, branching ratios and radiative lifetimes for the as-grown crystal were all calculated. The stimulated emission cross-section of the 3F4 → 3H6 transition was obtained by using the Fuchtbauer-Ladenburg method. The gain cross-section for ∼1.84 μm emission becomes positive once the population inversion level reaches 30%. The fluorescence lifetime of the 3F4 manifold was measured to be 15.56 ms. Potential utility of the Tm:LaF3 crystal as laser active material at ∼1.84 μm can be expected.

•A Ho-doped LaF3 sing crystal was successfully grown from the melt.•The spectral parameters of Ho:LaF3 crystal were calculated in detail.•Optical properties of Ho:LaF3 for 2 μm lasers were systematically studied for the first time.•Emission properties of Ho:LaF3 for 5I6 → 5I7 (2.9 μm) transition were reported for the first time.Optical properties of a Ho-doped LaF3 single crystal have been detailed investigated as a promising material for 2 μm and 2.9 μm lasers for the first time. Judd–Ofelt theory was applied to analyze the absorption spectrum to determine the J–O intensity parameters Ωt(t=2,4,6), based on which the emission probabilities, branching ratio and radiative lifetime for the as-grown crystal were all calculated. The stimulated emission cross-sections of the 5I7 → 5I8 and 5I6 → 5I7 transitions were obtained by using the Fuchtbauer–Ladenburg method. The gain cross-section for 2 μm emission becomes positive once the population inversion level reaches 30%. The Ho:LaF3 crystal shows long fluorescence lifetime of 5I7 manifold (25.81 ms) as well as 5I6 manifold (10.37 ms) compared with other Ho3+-doped crystals. It can be proposed that the Ho:LaF3 crystal may be a promising material for 2 μm and 2.9 μm laser applications.

A new red-emitting phosphor Ca9Lu(PO4)7:Ce3+, Mn2+ has been synthesized by solid-state reaction, and its luminescence properties have been investigated. The broad red emission peaked at 645 nm of Mn2+ is greatly enhanced by the sensitizer Ce3+ due to efficient energy transfer from Ce3+ to Mn2+. The energy transfer was demonstrated to belong to a resonant type via a dipole–quadrupole mechanism. The critical distance for Ce3+→Mn2+ energy transfer was calculated to be 15.04 Å by concentration quenching method. Preliminary results indicate that the phosphor might be a promising red phosphor for UV-based white LEDs.Highlights► We found a promising red-emitting phosphor Ca9Lu(PO4)7:Ce3+, Mn2+. ► It shows a broad emission band from 580 nm to 720 nm. ► The energy transfer mechanism from the Ce3+ to Mn2+ ions is a dipole-quadrupole interaction.

•Four Er-doped LiYF4 crystals with different Er-concentrations were grown.•Luminescence properties of the four crystals were analyzed in detail.•Heavily 15 at% Er-doped YLF crystal was found proper in up-conversion or ∼3 μm laser applications.Four Er-doped LiYF4 crystals with different Er-concentrations were grown by Czochralski method. The laser crystals were characterized by measurements of ICP-AES, XRD, absorption spectra, up-conversion fluorescence spectra, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence spectra, as well as luminescence decays. It was found that the heavily 15 at% Er-doped YLF crystal is more proper in up-conversion or ∼3 μm laser applications; while the 5 at% Er-doped YLF is a better candidate for ∼1.5 μm lasers within these four crystals.

Barium magnesium fluoride (BaMgF4—BMF) is a promising material for ultraviolet (UV) all solid-state lasers, but harmful scattering centers are always present in BMF crystals grown by the Czochralski method. In this work, scattering centers were observed only in the middle and upper parts of the as-grown crystals, whereas no light scattering was found in bottom parts. Furthermore, scattering centers can be removed by annealing at temperatures near the melting point, while they can also be created in the originally scatter-free crystals after being annealed at relatively low temperatures. Based on the results of post-growth heat treatments, the presence of a solid solution region near the melting point of BMF is proposed, and scattering centers were attributed to the precipitation of second-phase particles during crystal growth. Combining this hypothesis and the temperature distribution in the growth chamber, we are able to explain the scattering center formation mechanism and their inhomogeneous distribution in the as-grown crystals. This research will enable the growth of higher optical quality BMF crystals used in ultraviolet all solid-state lasers.