Transparent MgO ceramics were fabricated by spark plasma sintering (SPS) of the commercial MgO powder using LiF as the sintering additive. Effects of the additive amount and the SPS conditions (i.e., sintering temperature and heating rate) on the optical transparency and microstructure of the obtained MgO ceramics were investigated. The results showed that LiF facilitated rapid densification and grain growth. Thus, the MgO ceramics could be easily densified at a moderate temperature and under a low pressure. In addition, the transparency and microstructure of the MgO ceramics were found to be strongly dependent on the temperature and heating rate. For the MgO ceramics sintered at 900 °C for 5 min with the heating rate of 100 °C/min and the pressure of 30 MPa from the powders with 1 wt% LiF, the average in-line transmittance reached 85% in the range of 3 – 5 μm, and the average grain size is ∼0.7 μm.

•Highly transparent Co:MgAl2O4 ceramics were fabricated by vacuum pre-sintering combined with hot isostatic pressing.•The densification mechanism of Co:MgAl2O4 transparent ceramics was investigated systematically.•By HIP treatment, the in-line transmittance of Co:MgAl2O4 ceramics pre-sintered at 1500 °C for 5 h exceeds 80% at 2500 nm.•The ground state absorption cross section of 0.02 at.% Co:MgAl2O4 ceramics is calculated to be 3.35×10-19 cm2 at 1540 nm.•Co:MgAl2O4 transparent ceramics is promising as a saturable absorber for solid-state pulse laser operating at 1.5 μm.Cobalt-doped magnesium aluminate spinel (Co:MgAl2O4) is one of the most important saturable absorbers for the passive Q-switching of solid-state lasers operating at eye-safe wavelength of 1.5 μm. In this work, highly transparent Co:MgAl2O4 ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment, using the mixture of the commercial spinel and the lab-made Co:MgAl2O4 powder as the raw materials. The densification mechanism of Co:MgAl2O4 transparent ceramics was discussed. The microstructure and optical properties of the samples were investigated. The ground state absorption cross section (σGSA) was calculated from the fitted curve of the absorption coefficient spectrum. The results show that Co:MgAl2O4 ceramics fabricated by vacuum sintering at 1500 °C for 5 h and then HIP post-treatment at 1650 °C for 3 h perform good transparency, whose in-line transmittance exceeds 80% at 2500 nm. Moreover, the ground state absorption cross section of 0.02 at.% Co:MgAl2O4 ceramics is calculated to be 3.35 × 10−19 cm2 at the wavelength of 1540 nm, which is promising for the application to the passive Q-switching of solid-state laser operating in the near infrared region (NIR).

•LuYAG:Pr ceramic scintillators were prepared successfully without any additives.•With 0.15% Pr3+ doping, the prepared LuYAG:Pr ceramics displays a light output of 28500 ph/MeV at 3 μs shaping time.•The light yield of the obtained LuYAG:Pr ceramics is higher than that of the LuAG:Pr ceramic scintillators ever report.•The vacuum ultraviolet and electron spin resonance experiment were performed to explain the reason for this improvement.Y3+ admixing Lu3Al5O12:Pr ceramics are fabricated successfully by the solid state reaction method and further optimized by an air-annealing process. Optical absorption, photoluminescence spectra and scintillation properties such as radioluminescence, and light output are measured and compared with those of the Y3+ free LuAG:Pr ceramics. Positive effect of Y3+ codopant consists mainly in the significant increase of scintillation light output, as well as the decrease of relative intensity of slow component. With 0.15% Pr3+ codoping, the obtained LuYAG:Pr ceramic displays a light output of 28500 ph/MeV at 3 μs shaping time, higher than that of the LuAG:Pr ceramic scintillators ever report. The effect of Y3+ admixture is further explained by vacuum ultraviolet and electron spin resonance experiment.

•Fabrication, microstructure, optical transparency and laser performance of the planar waveguide ceramics are investigated.•In-line transmittance of the ceramic planar waveguide YAG/10at%Yb:YAG/YAG reaches 83.6% at 400 nm.•Planar waveguide ceramics realize an output power of 1.6 W at 1030 nm with a slope efficiency of 34.4%.Highly transparent YAG/10at.%Yb:YAG/YAG planar waveguide ceramics were fabricated by the non-aqueous tape casting and solid-state reactive sintering technology. The tapes are relatively homogeneous and the green body shows a dense structure without distinct interfaces after the treatment of debinding and cold isostatic pressing. YAG/10at.%Yb:YAG/YAG ceramics with almost full dense structure were obtained by vacuum-sintering at 1760 °C for 30 h. For the mirror-polished sample with the thickness of 3.5 mm, the In-line transmittance was measured to be 83.6% at the visual wavelength of 400 nm. The diffusion distance of the Yb3+ ions was about 215 μm along the thickness direction of the ceramics. In the lasing experiments, the YAG/10at.%Yb:YAG/YAG planar waveguide ceramics were end-pumped by a 976 nm semiconductor diode laser and enabled efficient continuous-wave lasers, which resulted in a maximum output power of 1.6 W and a slope efficiency of 34.4% at 1030 nm.

•“Sandwich” structure YAG/Nd:YAG/YAG ceramics were prepared by dry pressing and vacuum sintering of oxide powder mixture.•Different core (Nd3+ doped area) lengths of 1 mm, 5 mm and doping concentrations of 1 at.%, 2 at.% were investigated in detail.•Smaller average grain size was found in the specimen with the large core and high doping concentration.•With increase of core length, the optimum OC transmission increases and better laser performance can be obtained.•Long core length and high Nd3+ concentration bring the noticeable thermal lens effect and thermally induced birefringence.“Sandwich” structure YAG/Nd:YAG/YAG ceramics with different core (Nd3+ doped area) lengths of 1 mm, 5 mm and doping concentrations of 1 at.%, 2 at.% were prepared by dry pressing and vacuum sintering of oxide powder mixture. Smaller average grain size was found in the specimen with the larger core and higher doping concentration. With the increase of core length, the optimum transmission of output coupler increases from 10% to 19% and better laser performance can be obtained. However, longer core length causes the noticeable thermal lens effect, which influences the beam quality significantly. It is also reflected in the thermally induced depolarized beam pattern, which becomes more obvious with the longer core length and higher Nd3+ doping concentration.

•Yttria (Y2O3) ultrafine nanopowders were synthesized by a normal precipitation method.•5 at.%Yb:(La0.1Y1.9)2O3 transparent ceramics were fabricated by vacuum sintering at 1650 °C for 10 h using the precipitated yttria powders.•The in-line transmittance of the 5 at.%Yb:(La0.1Y0.9)2O3 ceramics is 81.3% at the wavelength of 1032 nm.•This prepared Yb:(La0.1Y1.9)2O3 transparent ceramics have the potential for high energy and short pulse lasers.Yttria (Y2O3) nanopowders were synthesized by a normal precipitation method using (NH4)2SO4 as dispersing agent. Pure Y2O3 powders without any other phase can be achieved by calcining the precursor at 600 °C for 4 h. The precursor and Y2O3 powders were characterized by TG-DTA, XRD, SEM and BET. In this work, 5 at.%Yb:(La0.1Y1.9)2O3 transparent ceramics were made by vacuum sintering at 1650 °C for 10 h. The in-line transmittance of the 5 at.%Yb:(La0.1Y0.9)2O3 ceramics is 81.3% at the wavelength of 1031 nm. The absorption cross-sections of the sample are calculated to be 1.20 × 10−20 cm2, 5.74 × 10−21 cm2 and 4.18 × 10−21 cm2 at 976, 951 and 906 nm, respectively. The emission cross-sections of the emission peak located at around 1031 and 1073 nm are 1.13 × 10−20 and 0.42 × 10−20 cm2, respectively.

•Well dispersed Tb4O7 powders were synthesized by the carbonate-precipitation method.•TAG transparent ceramics were vacuum sintered from the precipitated Tb4O7 powders.•The in-line transmittance of the TAG ceramics reaches 58.3% at 633 nm and the Verdet constant is −180.4 rad T−1 m−1.Tb4O7 nanopowders were synthesized by the precipitation method using ammonium hydrogen carbonate (AHC) as the precipitant. The influence of calcination temperature on the properties of Tb4O7 powders was investigated by FTIR, XRD and FESEM. It is found that 1000 °C is the optimum calcination temperature for Tb4O7 powders used for fabrication of Tb3Al5O12 (TAG) transparent ceramics, and the average particle size of the 1000 °C-calcined powder is about 150 nm. Using the 800 to 1100 °C-calcined Tb4O7 powders as raw materials, TAG transparent ceramics were fabricated by vacuum sintering at 1700 °C for 20 h. The sample sintered from 1000 °C-calcined Tb4O7 powders shows the best transparency, and its in-line transmittance is above 55% in the 500–1480 nm region, reaching 58.3% at the wavelength of 633 nm. The microstructures and the magneto-optical properties of the TAG ceramics sintered from 800 to 1100 °C-calcined Tb4O7 powders were also studied.

•Fine and low-agglomerated TAG powders were synthesized by co-precipitation.•TAG transparent ceramics were prepared by vacuum sintering and HIP post-treatment.•TAG ceramics fabricated have better magneto-optical properties than TGG crystals.Terbium aluminum garnet (TAG) precursor was synthesized by a co-precipitation method from a mixed solution of terbium and aluminum nitrates using ammonium hydrogen carbonate (AHC) as the precipitant. The powders calcined at different temperatures were investigated by XRD, FTIR and FESEM in order to choose the optimal calcination temperature. Fine and low-agglomerated TAG powders with average particle size of 88 nm were obtained by calcining the precursor at 1100 °C for 4 h. Using this powder as starting material, TAG transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) sintering. For the sample pre-sintered at 1700 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the average grain size is about 3.9 μm and the in-line transmittance is beyond 55% in the region of 500–1600 nm, reaching a maximum transmittance of 64.2% at the wavelength of 1450 nm. The Verdet constant at 633 nm is measured to be −178.9 rad T−1 m−1, which is 33% larger than that of the commercial TGG single crystal (−134 rad T−1 m−1).

•Ultra-fine and low agglomerated 5 at%Yb:Sc2O3 powders were synthesized by a co-precipitation method.•Yb:Sc2O3 transparent ceramics with transmittance of 73.9% at 1100 nm were fabricated by vacuum sintering at 1850 °C for 10 h.•The microstructures, the optical and spectroscopic properties of 5 at%Yb:Sc2O3 transparent ceramics were mainly investigated.Ytterbium doped scandium oxide (Yb:Sc2O3) nano-powders were synthesized by a co-precipitation method. Ammonium hydrogen carbonate (NH4HCO3) and ammonia sulfate ((NH4)2SO4) were used in the precipitation process as the precipitant and dispersing agent, respectively. Structural properties and morphology of the precursor and nano-powders were investigated by BET, XRD, and SEM measurements. Ultra-fine and low agglomerated 5 at%Yb:Sc2O3 powders with the average particle size of 86 nm were obtained after calcination of the precipitate at 1100 °C for 5 h, that was found to be the optimal temperature for preparation of 5 at%Sc2O3 powders for further sintering. 5 at%Yb:Sc2O3 transparent ceramics with in-line transmittance of 73.9% at 1100 nm and average grain size of 182 μm were fabricated by vacuum sintering of the optimal powder at 1850 °C for 10 h. The microstructure, the spectroscopic properties and the gain characteristics of obtained 5 at%Yb:Sc2O3 ceramics were also studied and discussed.

•Transparent Co:MgAl2O4 ceramics were fabricated by hot pressing with LiF addition.•The σgas of Co2+ in 0.05 at.% Co:MgAl2O4 ceramics is 2.55 × 10−19 cm2 at 1540 nm.•Co:MgAl2O4 optical ceramics is a promising saturable absorber for 1.5 μm pulse laser.Cobalt-doped magnesium aluminate spinel (Co:MgAl2O4) could be the most effective saturable absorber (SA) for Q-switching solid-state lasers operating at 1.5 μm. Using LiF as the sintering aid, highly transparent Co:MgAl2O4 ceramics were fabricated by hot pressing (HP) of the commercial spinel and the co-precipitated Co:MgAl2O4 powder mixture. The optical properties of Co:MgAl2O4 ceramics were investigated, and the ground state absorption cross section (σgas) of Co2+ was calculated from the curve of the absorption coefficient. For the Co:MgAl2O4 ceramics hot-pressed at 1600 °C for 2 h under 30 MPa with 1 wt.% LiF addition, the in-line transmittance reaches about 77% at 1000 nm and 1700 nm, and the ground state absorption cross section of Co2+ is 2.55 × 10−19 cm2 at the wavelength of 1540 nm, which is promising as a saturable absorber for solid-state pulse laser operating at 1.5 μm.

Transparent magnesium aluminate spinel (MgAl2O4) ceramics were fabricated by hot-pressing of the MgO and α-Al2O3 powder mixture using LiF as a sintering aid. Effects of the LiF additive on densification, microstructure and optical properties of MgAl2O4 ceramics were systematically investigated. It has been found that the addition of LiF can effectively remove the porosity and increase the optical transparency of MgAl2O4 ceramics. For the spinel ceramics HP-ed at 1550 °C for 3 h with 1 wt% LiF addition, the average grain size is about 36 µm and the in-line transmittance exceeds 60% at the wavelength of 800 nm.

•Pr,Mg:LuAG transparent ceramics were fabricated by solid-state reactive sintering.•Annealing in air below 900 °C improves the 5d-4f emission efficiency of Pr,Mg:LuAG.•Annealing at higher temperature deteriorates the luminescence properties of ceramics.Polycrystalline 0.2at%Pr:Lu3Al5O12 (Pr:LuAG) transparent ceramics were fabricated by solid-state reaction using 0.01 wt% MgO as sintering aid. The as-sintered ceramics were annealed in air at different temperatures. Optical absorption, photoluminescence, X-ray excited luminescence and pulse height spectra obtained after different annealing were compared. Modifications of the oxygen vacancy concentrations are found to govern the changes of the optical and scintillation response for annealing temperatures lower than 1000 °C, while the oxidation of Pr3+ to Pr4+ plays a more important role for higher temperatures. Air annealing up to 700 °C is an effective tool to improve the 5d-4f emission efficiency of MgO co-doped Pr:LuAG transparent ceramics. The highest radioluminescence intensity is obtained for the 700 °C annealed sample. At variance, higher temperature annealing leads to the deterioration of 5d-4f photoluminescence and scintillation properties because of the self-absorption of Pr4+ and energy transfer from Pr3+ to Pr4+. In addition, we find that the 4f-4f slow emission of ceramics shows different response characteristics under different irradiation sources.

Neodymium doped yttrium aluminum garnet (Nd:YAG) transparent ceramics were fabricated from Nd:YAG nanopowders synthesized via a reverse precipitation method by vacuum sintering and successive hot isostatic pressing (HIP) post-treatment. The powders obtained by calcining the precursor at 1100 °C for 4 h and then ball milling for 2 h with 0.5 wt% TEOS as sintering aid were used to fabricate Nd:YAG ceramics. The green bodies were vacuum sintered at 1500–1800 °C for 10 h, followed by the HIP at 1600 °C for 3 h in 200 MPa Ar atmosphere. Influence of the calcination temperature on the phase, morphology and particle size evolution of the nanopowders, as well as the optical transparency and microstructure of the obtained Nd:YAG ceramics before and after the HIP post-treatment was investigated in detail. It was found that for the post-treated 1800 °C-vacuum-sintered Nd:YAG ceramic sample, the in-line transmittance increased from 48.0% up to 81.2% at the lasing wavelength of 1064 nm.

•The Cr3+ doped LuAG transparent ceramics were rarely if ever reported, especially for scintillator use.•Cr3+:LuAG ceramics show a high steady state scintillation efficiency under X-ray excitation, comparable to the Ce3+ or Pr3+ doped LuAG ceramics.•The X-ray induced emission lies in 706 nm with a broad emission peak shape, demonstrating a red scintillator use.•The Cr:LuAG/Ce:LuAG dual layer structured composite ceramic demonstrated a broad and continuous emission from 400 nm to 800 nm.Cr3+ doped Lu3A15O12 transparent ceramics were developed as a new red scintillator ceramics. These ceramics were fabricated by a solid state reaction method under vacuum sintering at temperature range of 1550 °C–1890 °C for 10 h. The doping effect of different Cr3+ concentration (0, 0.1, 0.3 and 0.5 at. %) and air annealing effect were investigated as well. The transparent ceramics (70% @1 mm in visible light range) with dense microstructure were obtained when sintered at 1890 °C for 10 h, the average grain size of 0.3 at.% Cr:LuAG was calculated to be 7 μm. Photo-luminescence spectra revealed that there are two typical excitation bands at around 450 nm and 600 nm which were ascribed to the d–d transitions of Cr3+. 0.3 at. % Cr:LuAG exhibited the optimum photoluminescence intensity and fast decay. Radio-luminescence under X-ray excitation indicated a characteristic Cr3+ emission peaking at 687 nm and 706 nm respectively. The Lu3+Al antisite defects related emission at around 300 nm was observed to decrease with the doping of Cr3+. The steady luminescence efficiency (XEL spectrum integral) is around 20 times of the commercial BGO crystals, more important, the broad and continuous red emission between 600 nm and 800 nm demonstrated Cr:LuAG ceramics a prospective application as new red scintillators.

•Multi-component garnet Nd:Lu2.7Gd0.3Al5O12 transparent ceramics were fabricated for the first time.•The microstructures, optical transmission and spectroscopic characteristics of Nd:Lu2.7Gd0.3Al5O12 ceramics were studied.•Nd:Lu2.7Gd0.3Al5O12 transparent ceramics have the potential to be a new solid-state laser material.Transparent 1.0 at% Nd:Lu2.7Gd0.3Al5O12 (Nd:LuGdAG) ceramics were fabricated by the solid-state reactive sintering method using commercial powders as starting materials. The powders were mixed in ethanol with tetraethoxysilane (TEOS) and MgO, dried and pressed. The compacts were vacuum-sintered from 1725 °C to 1800 °C for observing the microstructure and the optical transmittance of Nd:Lu2.7Gd0.3Al5O12 ceramics. The sample sintered at 1800 °C for 10 h has an almost dense and homogenous structure with the average grain size of 12.8 μm, whose in-line transmittance is about 70% at 1064 nm. The absorption and emission cross sections were calculated to be 1.0 × 10−20 cm2 and 1.23 × 10−18 cm2, respectively. It is proved that Nd:LuGdAG ceramics have the potential to be a new solid-state laser material.

Highly transparent aluminum oxynitride (AlON) ceramics were fabricated by pressureless sintering with hot isostatic pressing (HIP) post-treatment. The experimental results showed that the optical transparency of AlON ceramics was improved markedly over the visible and near-infrared range by HIP at 1825 °C for 3 h in 200 MPa argon gas, which derived from the elimination of residual pores in the prepared ceramics. For AlON ceramics pre-sintered at 1800 °C, the transmittances of the sample increased from 63.6% to 84.8% at 600 nm and from 75.4% to 86.1% at 2000 nm, respectively. The average grain size of the HIPed sample was about 47.9 μm.

Nd:LuAG transparent ceramics were fabricated by a solid-state reaction method using commercial high-purity oxide powders as raw materials. The microstructure, optical transmittance, fluorescence spectrum and laser performance of 0.8 at.% Nd:LuAG transparent ceramics were investigated. It is found that the relative density and grain size for Nd:LuAG ceramics increase with the increase of sintering temperature. The specimen sintered at 1830 °C for 30 h is dense and homogeneous in structure with an average grain size of about 39.6 μm, whose in-line transmittances are 82.8% at 1064 nm and 81.8% at 400 nm. The main fluorescence emission peak is centered at about 1063.5 nm and the fluorescence lifetime is 240 μs. The optimum laser properties are obtained with the 300 μm pumping beam and 25% output coupler, corresponding to a slope efficiency of 43.4% and an optical–optical efficiency of 39.3%. In addition, the depolarization caused by the thermally-induced birefringence was also investigated.

Aluminum oxynitride (AlON) powders were synthesized by the carbothermal reduction and nitridation process using commercial γ-Al2O3 and carbon black powders as starting materials. And AlON transparent ceramics were fabricated by pressureless sintering under nitrogen atmosphere. The effects of ball milling time on morphology and particle size distribution of the AlON powders, as well as the microstructure and optical property of AlON transparent ceramics were investigated. It is found that single-phase AlON powder was obtained by calcining the γ-Al2O3/C mixture at 1550 °C for 1 h and a following heat treatment at 1750 °C for 2 h. The AlON powder ball milled for 24 h showed smaller particles and narrower particle size distribution compared with the 12 h one, which was benefit for the improvement of optical property of AlON transparent ceramics. With the sintering aids of 0.25 wt% MgO and 0.04 wt% Y2O3, highly transparent AlON ceramics with in-line transmittance above 80% from visible to infrared range were obtained through pressureless sintering at 1850 °C for 6 h.

•Homogeneous and ball-shaped yttria nano-powders were synthesized by the precipitation method.•Influences of R value on composition and morphology of precursor and yttria powders were mainly investigated.•Influence of ammonium sulfate addition on morphology of yttria powders was studied.Yttria (Y2O3) nano-powders were synthesized by the normal-strike precipitation method. The influences of R (NH4HCO3/M3+, molar ratio) and ammonium sulfate addition were studied throughout the preparation process. Several analytic techniques such as XRD, TG/DSC, SEM and FTIR were used to determine the characteristics of the precursors and Y2O3 powders. It was found that morphologies and phases of the precursors were evidently influenced by the R value. The phases of the precursors were Y2(CO3)3·2.79H2O when R was 3–4, while the composition of the precursors with R = 4–5 was (NH4)aY(OH)b(CO3)c·xH2O. Homogeneous needle-flake shaped particles composed of coadjacent grains with diameters of about 70 nm were obtained as the R = 3–4. The rhombohedral flake-shaped particles were the products with R = 5–6. The mechanism of the influence of R value on the precipitation of the precursor was also investigated in this work. Pure Y2O3 nano-powders were obtained by calcining the precursors at 1000 °C for 4 h regardless of what the R value was. Sulfate ions affect not only dispersion of nanopowders, but also their grain size. Results obtained in this work are contributed to the controllable synthesis of yttria powders.

•Highly transparent Yb:LuAG ceramics are prepared by the solid-state reactive sintering.•The comparison of physical properties between Yb:LuAG and Yb:YAG ceramics is observed in detail.•The microstructure, transmittance, fluorescence spectrum and laser performance of Yb:LuAG ceramics are investigated systematically.We reported on the fabrication and properties of 2.5 at.% Yb:LuAG ceramics prepared by a solid-state reactive sintering method using commercial available powders as starting materials. The Yb:LuAG ceramics sintered at 1850 °C for 50 h have a dense and homogeneous structure with the average grain size of about 60 μm. The transmittances of the Yb:LuAG ceramics with the 3 mm thickness are 82.6% at 400 nm and 84.0% at 1100 nm. The maximum luminescence peak is located at about 1029 nm and the fluorescence lifetime is 1.3 ms. It is demonstrated that the Yb:LuAG ceramics have excellent mechanical properties, furthermore the thermal expansivity and thermal conductivity are even better than those of Yb:YAG ceramics. Continuous-wave (CW) laser operation is obtained with the maximum output power of 2.1 W and a slope efficiency of 41.7% for non-coated Yb:LuAG ceramics with the output coupler of T = 10%.

Highly transparent Nd:YAG ceramics were fabricated by non-aqueous gelcasting and vacuum sintering for the first time, using epoxy resin and polyamine curing agent as gelling system. The influences of dispersant, solid loading and the organics of gelling system on the viscosity of suspensions and the stability of suspensions were discussed. The optimized nonaqueous slurry was of 54 vol% solid loading, comprising the commercial α-Al2O3, Nd2O3 and Y2O3 powders. The slurry with low viscosity and good fluidity was obtained by using 0.45 wt% PEI as dispersant. The homogenous and dense green body was obtained through solidificating the slurry in-situ. The green body after burnout had a relative density of 55.0% with a narrow pore size distribution. The transmittance of the Nd:YAG ceramics sintered at 1775 °C for 30 h with the thickness of 1.5 mm reached 83% at 1064 nm. The average grain size of the sample was about 71 μm.

•A silica optical fiber doped with yttrium aluminosilicate (YAS, Y2O3–Al2O3–SiO2) nanoparticles in the core was designed and fabricated.•The YAS nanoparticles in the fiber core can improve the nonlinearity.•Supercontinuum generation by multiple solitons and dispersive waves was obtained.We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y2O3–Al2O3–SiO2) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y3Al5O12) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950 °C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750 nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500 nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7 dB uniformity is obtained at the wavelength region of ∼990–1980 nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100 nm, a narrow SC spectrum from ∼1020 to 1180 nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

•TAG transparent ceramics were fabricated by the solid-state reactive sintering at 1700 °C for 20 h.•The Verdet constant of TAG ceramics is −179.4 rad. T−1 m−1 at 633 nm, much larger than that of TGG single crystal.•The TAG glass exhibits high optical transmittance and excellent magneto-optical properties.Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics were fabricated by the solid-state reactive sintering of a mixture of commercial Tb4O7 and α-Al2O3 powders with tetraethoxysilane (TEOS) and MgO as sintering aids. Samples sintered at 1700 °C and 1725 °C for 20 h were utilized to examine the phase compositions, optical quality, microstructure and magneto-optical property. X-ray diffraction (XRD) results show that the sample sintered at 1700 °C has a pure garnet crystal structure, while the characteristic diffraction peaks of TAG disappear when sintered at 1725 °C. The sample sintered at 1725 °C shows high transparency and the optical transmittance is beyond 80% in the region of 600–1500 nm. It is found that the sample sintered at 1700 °C exhibits homogeneous grains with the average size of about 5.97 μm, however, no TAG grains are observed in the sample sintered at 1725 °C. The Verdet constants of the samples sintered at 1700 °C and 1725 °C are −179.4, −179.3 rad T−1 m−1 at 633 nm, respectively. The thermal depolarization of the sample sintered at 1725 °C increases up to 2 × 10−4 at maximum laser power of 91 W, which corresponds to the isolation ratio of 37 dB.

•High quality Er3+:YAG transparent ceramics have been prepared.•Z-scan technique was used to characterize the nonlinear response of the Er3+:YAG ceramics.•The third-order nonlinear optical parameters of Er3+:YAG ceramics have been obtained.By performing the Z-scan measurements with ultrafast femtosecond laser centered at 800 nm wavelength, we can unambiguously distinguish the real and imaginary part of the third-order optical nonlinearity of the erbium-doped YAG ceramics. The reverse saturable absorption of the erbium-doped YAG ceramics has been observed experimentally, and the nonlinear refractive index of the ceramics is estimated to be about 10−21 m2/W. The experimental results may provide design guidelines for the high power laser design and its applications.

•Designed and made a fiber laser operating at 1940 nm with a slope efficiency of 40.6%.•Passively Q-switched Ho:YLF laser pumped by Tm3+-doped fiber laser.•Achieved 15.6 ns single pulse width with 2.3 kHz pulse repetition frequency.We demonstrate a compact and efficient passively Q-switched (PQS) Ho:YLF laser pumped by a self-made all-fiber laser. Firstly, we design and make an all-fiber laser operating at 1940 nm with a slope efficiency of 40.6%. Then, the all-fiber laser was used to pump Ho:YLF laser directly. In the CW (continues-wave) operation Ho:YLF laser, the maximum output power was 7.79 W, corresponding to the slope efficiency of 55.2%. Using Cr2+:ZnS as the saturable absorber, the average power of 6.03 W was achieved with the slope efficiency of 45.9%. The shortest pulse duration was 15.6 ns and the pulse repetition frequency was 2.3 kHz at the pump power of 20.4 W. The pulse energy was a constant as 2.7 mJ when the pump power exceeded 15 W. The beam quality factor of M2 was 1.05, indicating nearly diffraction limited beam propagation.

Well-dispersed yttria nanopowders were synthesized by a precipitation method from yttrium nitrate solution using ammonium hydrogen carbonate as a precipitant. Needle-like precursor Y2(CO3)3·2.79 H2O undergoes fragmentation and decomposition into isolated quasi-spherical Y2O3 particles upon calcination in air. Highly transparent YAG ceramics were fabricated from the as-synthesized Y2O3 powder and the commercial α-Al2O3 powder by vacuum sintering. Phase transformation, morphology evolution, and sinterability of Y2O3 powders, microstructure and optical properties of YAG ceramics were investigated in detail. The densification, grain growth, linear shrinkage and phase transformation of the as-sintered ceramics were also explored. The activation energy for grain growth in the ceramic sample is 881 kJ/mol. With optimized preparation conditions, YAG ceramics with the average grain size of about 20 μm were fabricated by sintering at 1780 °C for 20 h, whose in-line transmittance reached 83.7% and 80.3% at the wavelength of 1064 nm and 400 nm, respectively.

Highly transparent 2 at.% Nd:YAG ceramics were prepared by a solid-state reaction sintering method using commercial high-purity powders of α-Al2O3, Y2O3 and Nd2O3. For the Nd:YAG ceramics sintered at 1750 °C for 50 h, a dense and pore-free microstructure with average grain size of about 15 μm was obtained, whose in-line transmittances reached 84.2% at 1064 nm and 81.7% at 400 nm, respectively. As the surface conditions of Nd:YAG ceramic influence the laser behavior significantly, especially the laser-induced damage, the interaction between laser and Nd:YAG ceramics was mainly investigated. Three kinds of Nd:YAG ceramics with different surface roughness were prepared by different polishing processes. It was found that the surface roughness influenced the laser-induced damage threshold significantly. In addition, we also calculated the laser-induced damage threshold and observed the damage morphology of ceramics.

The sintering behavior of neodymium doped yttrium aluminum garnet (Nd:YAG) ceramics was investigated on the basis of densification trajectory, microstructure evolution and transmittance. Nd:YAG ceramics with in-line transmittance of 83.9% at 1064 nm and 82.5% at 400 nm were obtained by direct cold isostatic pressing (CIP) at 250 MPa and solid-state reactive sintering at 1790 °C for 30 h under vacuum. Compared with the porosity and the average pore diameter of the sample from uniaxial dry-pressing followed by CIP, those from direct CIP are much smaller. The samples pressed at 250 MPa were sintered from 1500 °C to 1750 °C for 0.5–20 h to study their sintering behavior. At the temperature higher than 1500 °C, pure YAG phase is formed, followed by the densification and grain growth process. The relative density and the grain size increase with the increase of sintering time and temperature, and the sintering behavior is more sensitive to temperature than holding time. The mechanism controlling densification and grain growth at sintering temperature of 1550 °C is grain boundary diffusion.

Transparent Nd:YAG ceramics were fabricated by solid-state reactive sintering of Y2O3, α-Al2O3 and Nd2O3 powders with TEOS and MgO as sintering aids. The powders were ball-milled, dried, sieved and calcined at different temperatures. Samples sintered at 1745 °C for 10 h were utilized to observe the microstructure and the optical transmission. It is found that heat treatments of the powder mixtures above 600 °C for 1 h are necessary to remove the carbon contamination but below 800 °C for 4 h can avoid strong aggregation of the powder. So there is a room for heat-treatment, between 600 °C and 800 °C that can obtain Nd:YAG ceramics with almost pore-free microstructures and high transparency. Highly transparent Nd:YAG ceramic with 84.3% in-line transmission at 1064 nm was fabricated by sintering the 800 °C-1 h-heat-treated powder mixture at 1745 °C for 50 h. Even at wavelength of 400 nm, the transmittance of the sample reached 82.9% and the optical scattering coefficient was as low as 0.71% cm−1.

•Fabrication of YAG transparent ceramics by solid-state reactive sintering.•Phase transformation, densification, microstructure evolution of Nd:YAG ceramics.•Investigation on grain growth kinetics of Nd:YAG ceramics.•Influence of sintering conditions on optical transmission of Nd:YAG ceramics.Transparent polycrystalline YAG ceramics were fabricated by solid-state reactive sintering of a mixture of commercial α-Al2O3 and Y2O3 powders with tetraethoxysilane (TEOS) and MgO as sintering aids. Pressed samples were sintered from 1500 °C to 1750 °C in vacuum. Phase transformation, densification, microstructure evolution, grain growth kinetics and optical transparency of YAG ceramics were examined. Fully dense YAG transparent ceramic with average grain size about 17 μm was obtained by vacuum sintering at 1730 °C for 10 h and the in-line transmittance of the sample was 80.9% at 1064 nm wavelength. The maximal transmission 82.8% was demonstrated for the sample sintered at 1730 °C for 20 h, whose average grain size was about 22 μm. These pure YAG ceramics can be used for optical windows applications.

•Heat-treatment in oxygen may decrease the internal porosities of Y2O3 powders.•Heat-treatment of Y2O3 improved the size matching with Al2O3 after milling.•Pretreatment of Y2O3 powders optimized the microstructure of Nd:YAG ceramics.•Heat-treatment of Y2O3 powders improved the transparency of Nd:YAG ceramics.Influence of Y2O3 commercial powders preheat-treating in oxygen atmosphere on solid-state reactive sintering of Nd doped yttrium aluminum garnet (Nd:YAG) transparent ceramics was investigated. The ceramics were fabricated by solid-state reactive sintering of commercial α-Al2O3, Nd2O3 and either untreated or heat-treated Y2O3 powders. It was found that the preliminary heat-treatment of the Y2O3 powders in oxygen atmosphere may reduce the internal porosities of the Y2O3 powder and optimize the matching with α-Al2O3 powder, increases relative density of the green body and transparency of ceramics. The highest transparency was achieved when the Y2O3 powder was pretreated at 1000 °C. The in-line transmittances are 83.7% and 82.1% at the wavelength of 1064 nm and 400 nm, respectively. Basic reasons of the Y2O3 powders preheat-treatment influence on the microstructure and optical transmission of Nd:YAG transparent ceramics were established.

Transparent YAG ceramics were prepared by the aqueous and non-aqueous based tape casting methods. The rheological property of the slurries was analyzed by the viscosity–shear rate curves. The thermal character was detected by the TG–DTA analysis. The microstructures of the tapes and ceramics were compared. The influence of density of the tape on the ceramics were discussed. The in-line transmittance curves were compared to analyze the optical quality of obtained samples. Results indicate that the methods mentioned above can achieve transparent YAG ceramics with multilayer structure. The transmittance of the sample prepared by the aqueous tape casting is above 81% at 400 nm and the sample fabricated by the non-aqueous tape casting possesses higher optical properties. The transmittance is higher than 82% at 400 nm and reaches 84% at 1064 nm.

The suspensions of the powder mixture of yttria and alumina were prepared by the aqueous tape casting method. Rodia DP270, Dolapix CE64, citric acid and Dammonium 3008 were used as dispersing agents. The morphologies of the powders and the fracture surface of the green body were observed by scanning electron microscopy (SEM). The zeta potential test was employed to characterize the surface charge states of different suspensions. The dispersion of the suspensions was analyzed by the rheological tests and the sedimentation experiments. The results indicated that the yttria and alumina powder mixtures were well dispersed by the dispersing agents. The rheological curves showed shear thinning behavior. The most efficient dispersing agent was Dammonium 3008. The optimum usage of Dammonium 3008 was 1.0 wt.%. The green body was dense and no interface between the adjacent layers was found. The in-line transmittance of the as-sintered YAG ceramic was higher than 80% between 400 and 1100 nm.Rheological curves as a function of various dispersing agents (1) No dispersant; (2) Citric acid; (3) Dolapix CE64; (4) Rhodia DP270; (5) Dammonium 3008

Yttrium aluminum garnet (YAG) precursor was synthesized via a coprecipitation method with aluminum nitrate and yttrium nitrate as raw materials, using ammonium hydrogen carbonate (AHC) as the precipitant. Fine and low-agglomerated YAG powder was obtained by calcining the precursor at 1200 °C. The primary crystallites were measured to be ∼120 nm in size and weakly agglomerated to a particle size of ∼500 nm, indicating a high degree of sinterability. With 0.5 wt% tetraethyl orthosilicate (TEOS) and 0.1 wt% magnesia as sintering aids, transparent YAG ceramics were fabricated by vacuum sintering at 1730–1790 °C for various hours. The influences of sintering temperature and holding time on the microstructure and transmittance of YAG ceramics were discussed.

Highly transparent 1.0 at%Nd:YAG laser ceramics were fabricated by solid-state reaction and vacuum sintering. The densification, the microstructure evolution, the optical, the mechanical and the thermal properties of the Nd:YAG ceramics were investigated. Fully dense Nd:YAG ceramic with average grain size of ∼15 μm was obtained by sintering at 1720 °C for 30 h. The grain boundary was clean and no secondary phase was observed. The in-line transmittance was 82.5% at 1064 nm. The absorption coefficients at 808 nm and 1064 nm were 4.52 cm−1 and 0.16 cm−1, respectively. The fluorescence spectrum for Nd:YAG ceramic was almost identical with single crystal and the fluorescent lifetime was 257 μs. With 341 mW of maximum absorbed pump power, laser output of 26 mW has been obtained with an oscillation threshold and a slope efficiency of 100 mW and 11.8%. The Vicker’s hardness, Young’s modulus, bending strength, fracture toughness values were 12.5 GPa, 221 GPa, 229 MPa and 2.21 MPa m1/2, respectively. The thermal conductivity at room temperature was 9.7 W/m K and the average linear thermal expansion coefficient from 30 to 1000 °C was 8.713 × 10−6 K.

•Single-longitudinal-mode Ho:YAG ceramic laser is demonstrated for the first time.•A 1908 nm all-fiber Tm-doped fiber laser was used as pump source.•By inserting etalons, the maximum single-longitudinal-mode output power was 530 mW.•Single-longitudinal-mode operation in the range of 2091.1–2092.1 nm was demonstrated.We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M2 factor was measured to be 1.23.

Transparent Fe2+:ZnS polycrystals are 3–5 μm mid-IR laser gain materials with great importance. In this paper, a novel route combining wet-chemical co-precipitation, hot-pressed sintering and post hot isostatic pressing (HIP) treatment was proposed for Fe2+:ZnS transparent ceramics. Fe2+:ZnS powders were synthesized successfully by the wet-chemical co-precipitation method, which was suitable for particle size and morphology controlling and then ceramics consolidation. Transparent Fe2+:ZnS ceramics with comparatively high optical quality were successfully fabricated by two step sintering method combining hot pressing and post-HIP treatment. This approach is a promising candidate for fabricating Fe2+:ZnS ceramics with large size, low cost, short cycle, and flexible concentration distribution design.

In this paper, (Lu,Gd)2O3:Eu ceramics were consolidated by the solid-state reaction method combined with vacuum sintering at 1820 °C for 10 h. It is found that the Gd2O3 incorporates well into the Lu2O3 lattices and forms a solid solution. Particularly, strong red emission of 5D0→7F2 transition of Eu3+ at 611 nm, matched well to the spectral sensitivity of typical CCD arrays, was observed in the photoluminescence and radioluminescence spectra. What's more, radioluminescence intensity of the 4f→4f transitions of Eu3+ reaches up to 10 times of bismuth germanium oxide (BGO) single crystal reference scintillator. Intensities of the radioluminescence and the integrated thermoluminescence versus temperatures, as well as the influence of annealing treatment on the thermoluminescence intensity, were also studied. We think that (Lu,Gd)2O3:Eu ceramic scintillators may have great potential in medical X-ray computed tomography (CT) due to their excellent properties.