Search

SrHfO3:Ce and SrHfO3:Ce,Al powders were prepared by the solid-state synthesis using the commercial HfO2, SrCO3, CeO2 and α-Al2O3 as the starting materials. All the SrHfO3:Ce and SrHfO3:Ce,Al powders calcined at different temperatures within 1100 °C–1300 °C for 8 h in air exhibited a pure SrHfO3 phase. Meanwhile, the effects of different calcination temperatures and co-doped alumina on the microstructure of SrHfO3:Ce,Al powders were discussed. SrHfO3:Ce and SrHfO3:Ce,Al ceramics were successfully fabricated via the vacuum sintering at 1800 °C for 20 h. The alumina acted as the sintering aid, which promoted the densification and eliminated the intragranular pores of SrHfO3:Ce,Al ceramics. The charge disbalance was effectively compensated by co-doped alumina. SrHfO3:Ce,Al ceramics exhibited a higher light yield of 5700 ph/MeV compared with 4600 ph/MeV obtained in SrHfO3:Ce ceramics. The charge traps in ceramics and their effects on scintillation properties were also investigated by thermoluminescence measurement.

Several sets of Eu-doped Y3Al5O12 (YAG) ceramic samples were synthesized by the vacuum sintering technique. Their structural, optical and magnetic properties were investigated by means of X-ray diffraction, X-ray fluorescence, optical absorption, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Multiple annealing in different atmospheres was employed to understand the nature of strong specific absorption bands peaking at about 250, 370 and 550 nm in the case of these ceramics. The influence of sintering aids used during the preparation of ceramics (such as tetraethyl orthosilicate and/or magnesium oxide) on the optical properties is thoroughly studied. The charge transfer transition in the EuY2+ + F+ pair center is suggested to explain the nature of these absorption bands which is also supported by the peculiarities of the Eu2+ 5d–4f and F+/F luminescence occurrence. Application potential of the studied ceramics in the industrial implementation is discussed as well.

Pr:Lu3Al5O12 transparent ceramics with different doping concentrations (0% − 1 at%) were fabricated using the solid-state reaction and vacuum sintering method. The influence of doping concentration on the luminescent properties was investigated in detail. The 5d-4f emission slightly redshifts with the increase of doping concentration under UV light and X-ray excitation. The slow emission below 290 nm related to antisite defects can be suppressed by the increase of doping concentration at room temperature. The suppression of exciton related emission around 250 nm at 77 K is remarkable. The 0.3 at% Pr doped ceramics show the highest light yield that is 6900 ph/MeV with 1 μs shaping time under the excitation of γ-rays (137Cs). There exists slow components of scintillation process in all the Pr-doped transparent ceramics. Higher doping concentration was found to be beneficial for the suppression of the slow components in the scintillation response and therefore acceleration of the scintillation decay and light yield increase up to certain level. These effects are mainly due to competition of Pr3+ ions with the antisite defects for charge carrier capture in the scintillation process which is also supported by the trends observed in the TSL measurements.

Planar waveguide LuAG/10 at.%Yb:LuAG/LuAG laser ceramics were fabricated by the tape casting method combined with the vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment. The morphologies of the raw materials, tapes and green bodies were observed. The microstructure, optical transmittance and the Yb3+ ions distribution of the LuAG/10 at.%Yb:LuAG/LuAG ceramics with different pre-sintering temperatures after HIP post-treatment were mainly studied. The experimental results showed that the average grain size and in-line transmittance of the HIPed ceramics increased with the increase of pre-sintering temperature. For the LuAG/10 at.%Yb:LuAG/LuAG ceramics pre-sintered at 1825 °C for 20 h and then HIPed at 1700 °C for 3 h under 200 MPa Ar atmosphere, the in-line transmittance of the sample with the thickness of 2 mm was about 74% at 1100 nm and the maximum diffusion distance of Yb3+ was about 166 μm. The bulk and grain boundary diffusion coefficients of Yb3+ ions for the samples pre-sintered at 1775 °C–1825 °C after HIP post-treatment were calculated by Fick's second law by using the LA-ICP-MS. What's more, CW laser at 1030 nm was demonstrated and the maximum output power of 0.4 W with a slop efficiency of 9.4% was achieved.

Planar waveguide laser is a promising candidate for high power solid state lasers. Normally the native inhomogeneous refractive index exists during fabrication process, this will apparently affect power scaling and beam quality. Few quantitative works have been reported to the optimization of this behavior and in practice, try and error routine is needed to set pump conditions. In this work, we manufactured a miniature composite Yb:YAG ceramic waveguide laser via non-aqueous tape casting method, refractivity index gradience is natively generated via border diffusion between the Yb:YAG and YAG layers. We found a simple and effective criterion to treat pump optimization by combining wave optics model and laser rate equations. Guided by this criterion, we obtained an experimental slope-efficiency about 66% with optimized pumping beam parameters. This method could be forward applied in similar designs and much higher power planar waveguide lasers.

Cerium doped terbium aluminum garnet (Ce:TAG) magneto-optical ceramics with different doping concentrations were fabricated using the co-precipitated powders. All the as-synthesized powders exhibit a pure TAG phase and show good dispersity. Highly transparent Ce:TAG ceramics were then successfully fabricated by pre-sintering at 1650 °C for 20 h and HIP post-treating at 1700 °C for 3 h. The 0.5at% Ce:TAG ceramic shows the best transparency, and its transmittance is ~80% in the 600–1500 nm range. The Vertdet constant at 633 nm of the 2.0at% Ce:TAG ceramics is −196.2 rad T−1 m−1, which is 46% larger than that of the commercial TGG single crystals.

Sintering aids may enter the host lattice, create defects, and seriously deteriorate the scintillation properties of ceramic scintillators. In this study, the 0.3at%Pr:LuAG ceramics with different excess of Lu were fabricated by the solid-state reactive sintering without aids. The influences of stoichiometry on the sintering behaviors, optical and scintillation properties of the ceramics are systematically studied. The results show that the stoichiometric ceramics experience an abnormal grain growth during sintering. The Lu excess can restrain the abnormal grain growth of the ceramics because of the impurity drag effect. The excess Al2O3 as optical scattering centers, can also pin in the grain boundary to limit the fast migration of the grain boundaries. The light yield value of the as-sintered ceramics decreases with the increase of Lu content. After air-annealing, the ceramics with appropriate excess of Lu can achieve better optical quality and higher light yield compared to the stoichiometric Pr:LuAG ceramics.

Cr2+:ZnS is an important mid-infrared laser material, and Cr2+:ZnS nanopowders are very important for the fabrication of transparent ceramics. In this paper, Cr2+:ZnS nanopowders were synthesized via a hydrothermal method, in which thioacetamide (TAA) was adopted as sulfur source and reducing agent to avoid the oxidation of Cr2+ ions. The influences of the hydrothermal time and [Zn2+]/[TAA] ratio on the morphology and particle size of the nanopowders were investigated systematically as well as the reaction mechanism. It is believed that the orientated attachment and Oswald ripening both occurred during the hydrothermal reaction, which resulted in the formation of bimodal particle size distribution. After calcination of the nanopowders under Ar/H2 atmosphere, the Cr2+ ions were successfully doped into the Zn2+ lattice sites, which was supported by the X-ray powder diffraction patterns, the absorption and photoluminescence spectra of the calcination products. The optical properties were similar with those of the samples obtained by thermal diffusion, which means that they have the potential application in the fabrication of Cr2+:ZnS transparent ceramics.

A novel magneto-optical material, (Tb0.995Ho0.005)3Al5O12 transparent ceramic, was successfully fabricated using co-precipitated powders. The prepared (Tb0.995Ho0.005)3Al5O12 ceramic exhibits outstanding optical quality and magneto-optical property. For the (Tb0.995Ho0.005)3Al5O12 ceramic pre-sintered at 1650 °C for 20 h with HIP post-treatment at 1700 °C for 3 h, the optical transmittance exceeds 80% in the 500–1500 nm region (except for the absorption bands). The Verdet constant of the sample at 633 nm is about 1.4 times higher than that of the commercial Tb3Ga5O12 single crystal. High transparency and Verdet constant make it an attractive magneto-optical material for the high-power Faraday isolators.

Highly transparent terbium aluminum garnet (Tb3Al5O12, TAG) magneto-optical ceramics were fabricated from co-precipitated nanopowders with tetraethoxysilane (TEOS) as sintering aid by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The ball milled TAG powder shows better dispersity than the as-synthesized powder, and its average particle size is about 80 nm. For the ceramic sample pre-sintered at 1720 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the in-line transmittance exceeds 76% in the region of 400–1580nm (except the absorption band), reaching a maximum value of 81.8% at the wavelength of 1390 nm. The microstructure of the TAG ceramic is homogeneous and its average grain size is approximately 19.7 μm. The Verdet constant of the sample is calculated to be −182.7 rad·T−1·m−1 at room temperature.

In this paper, (Lu1-xGdx)2O3:Eu (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) ceramics were consolidated by the solid-state reaction method combined with vacuum sintering without sintering aids. We investigated the effect of the varying contents of Gd2O3 on the structure and spectroscopic properties of (Lu1-xGdx)2O3:Eu ceramics. X-ray diffraction (XRD) patterns indicate that proper amount of Gd2O3 can incorporate well with Lu2O3 and form Lu2O3-Gd2O3 solid solution. However, excessive Gd3+-doping in Lu2O3 will lead to the cubic phase transforming into monoclinic even hexagonal phase. The Gd3+ substitution no more than 50% of Lu2O3 enhances the radioluminescence, and reduces the fluorescence lifetime. Transmittance, photoluminescence, and radiation damage of the (Lu1-xGdx)2O3:Eu scintillation ceramics were also studied.

Hot-pressing of infrared transparent ZnS ceramics from nanopowders calls for proper particle size of the raw nanopowders to avoid the size-induced low-temperature sphalerite-to-wurtzite phase transition during calcination and sintering. In this paper, ZnS precipitate was solvothermally treated at 180 °C for 10–50 h. After solvothermal treatment, the particle size increased from 4 nm of the as-prepared precipitate to more than 10 nm, which results in better sphalerite phase stability. Even after calcination at 800 °C for 2 h, the major phase of the solvethermally synthesized powders kept as sphalerite phase. Due to the optically isotropic sphalerite phase, as well as the less organic impurities, the hot-pressed ceramic showed much better optical quality than that from the precipitated powders.

Cobalt-doped magnesium aluminate spinel (Co:MgAl 2 O 4 ) 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:MgAl 2 O 4 ceramics were fabricated by hot pressing (HP) of the commercial spinel and the co-precipitated Co:MgAl 2 O 4 powder mixture. The optical properties of Co:MgAl 2 O 4 ceramics were investigated, and the ground state absorption cross section (σ gas ) of Co 2+ was calculated from the curve of the absorption coefficient. For the Co:MgAl 2 O 4 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 Co 2+ is 2.55 × 10 −19 cm 2 at the wavelength of 1540 nm, which is promising as a saturable absorber for solid-state pulse laser operating at 1.5 μm.

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.

Terbium aluminum garnet (Tb 3 Al 5 O 12 , TAG) nanopowders were synthesized by the co-precipitation method using ammonium hydrogen carbonate (NH 4 HCO 3 , AHC) as the precipitant. The influence of ammonium hydrogen carbonate to metal ions molar ratio (AHC/M 3+ , R value) on the properties of TAG precursors and powders was investigated by FTIR, XRD and FESEM. It is found that the compositions of the precursors are nearly the same, and all the 1100°C-calcined powders exhibit a pure TAG phase. However, the R value has a significant influence on the morphology and agglomeration degree of TAG precursors and final powders. The precursor with R=3.6 shows a strong agglomeration, which is retained in the resultant powder. For the TAG precursors and powders with R=4.0, 4.4 and 4.8, they show better dispersity and homogeneity. Using the obtained powders as starting materials, TAG transparent ceramics were successfully fabricated by pre-sintering at 1700 °C for 20 h and then HIP post-treating at 1700 °C for 3 h. The ceramic sample with R=4.0 shows the best transparency, and its in-line transmittance exceeds 55% in the region of 500–1600 nm, reaching about 64% at 1450 nm. The microstructures and the magneto-optical properties of the TAG ceramics with different R values were also studied.

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.

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.

A diode-double-face-pumped Nd:YAG ceramic slab laser amplifier with uniform gain distribution and low depolarization loss was presented. Energy storage of 2.6 J was achieved at 1064 nm with a repetition rate of 200 Hz and a pulse width of 200 us from a 140 mm × 40 mm × 7 mm ceramic slab at a total pump power of 1215 W, corresponding to an optical-to-optical efficiency of 42.8%. An average small signal gain of 5.45 was achieved with a standard deviation of only 0.09 in the cross section, which shown good concentration uniformity. An average depolarization loss of 2.6% at different positions of the slab was obtained due to small thermal gradient of the zigzag configuration.

“Sandwich” structure YAG/Nd:YAG/YAG ceramics with different core (Nd 3+ 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 Nd 3+ doping concentration.

Yttria (Y 2 O 3 ) nanopowders were synthesized by a normal precipitation method using (NH 4 ) 2 SO 4 as dispersing agent. Pure Y 2 O 3 powders without any other phase can be achieved by calcining the precursor at 600 °C for 4 h. The precursor and Y 2 O 3 powders were characterized by TG-DTA, XRD, SEM and BET. In this work, 5 at.%Yb : (La 0.1 Y 1.9 ) 2 O 3 transparent ceramics were made by vacuum sintering at 1650 °C for 10 h. The in-line transmittance of the 5 at.%Yb:(La 0.1 Y 0.9 ) 2 O 3 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 cm 2 , 5.74 × 10 −21 cm 2 and 4.18 × 10 −21 cm 2 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 cm 2 , respectively.

The phoswich detectors can determine the location of nuclear interactions with the matrix and it is an effective approach to improve the spatial resolution at the edge of the field of view in positron emission tomography. In this study, we proposed a kind of bilayer structure garnet ceramic scintillators for phoswich detectors. Bilayer Pr:LuAG/Ce:LuAG ceramic scintillations with different thickness ratio were fabricated through solid-state reaction and vacuum sintering without further cutting or stacking process. The phase, microstructure, fluorescence and scintillation properties were characterized and studied. The decay time of the Pr:LuAG layer was about 21.8 ns while that of the Ce:LuAG layer was 58.6 ns. Different 5d-4f emission bands of 290–450 and 475-700 nm were observed in the Pr:LuAG layer and Ce:LuAG layer, respectively. These two features meet the basic requirements of phoswich detectors. Separation of interactions with γ-ray in different layers has achieved in the pulse height spectra. These properties reveal that this kind of mutilayer structure garnet ceramic scintillators have potential application value in the field of phoswich detectors. This article is protected by copyright. All rights reserved.

Gradient ceramics based on (1-x)PZT + xBiFeO3(x = 0.01, 0.05, 0.10, Zr/Ti = 95/5) were prepared by a conventional solid-state reaction process. The perovskite structure in the system was confirmed ...

Cobalt-doped magnesium aluminate spinel (Co:MgAl 2 O 4 ) 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:MgAl 2 O 4 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:MgAl 2 O 4 powder as the raw materials. The densification mechanism of Co:MgAl 2 O 4 transparent ceramics was discussed. The microstructure and optical properties of the samples were investigated. The ground state absorption cross section (σ GSA ) was calculated from the fitted curve of the absorption coefficient spectrum. The results show that Co:MgAl 2 O 4 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:MgAl 2 O 4 ceramics is calculated to be 3.35 × 10 −19 cm 2 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).

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.

Y 3+ admixing Lu 3 Al 5 O 12 :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 Y 3+ free LuAG:Pr ceramics. Positive effect of Y 3+ 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% Pr 3+ 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 Y 3+ admixture is further explained by vacuum ultraviolet and electron spin resonance experiment.

Transparent Fe 2+ :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 Fe 2+ :ZnS transparent ceramics. Fe 2+ :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 Fe 2+ :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 Fe 2+ :ZnS ceramics with large size, low cost, short cycle, and flexible concentration distribution design.

Transparent 1.0 at% Nd:Lu 2.7 Gd 0.3 Al 5 O 12 (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:Lu 2.7 Gd 0.3 Al 5 O 12 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 cm 2 and 1.23 × 10 −18 cm 2 , respectively. It is proved that Nd:LuGdAG ceramics have the potential to be a new solid-state laser material.

A comprehensive study of the optical, radioluminescence and scintillation properties of both the Lu3+ rich and Lu3+ deficient non-stoichiometric Lu3+xAG:Ce,Mg (Lu3+xAl5O12:Ce,Mg, x = −4, −1, +1 and +4 at.%) ceramics are performed, completed further by the microstructure and defects characterization. Small deviation from the stoichiometric composition as well as Mg2+ codoping plays a crucial role in ceramic transparency, radioluminescence intensity and the timing characteristics of scintillation response. The LuAl antisite defects could be suppressed efficiently by controlling Lu3+ content below stoichiometry of LuAG host. MgO (Mg2+ ions) as effective sintering aids, can improve both the optical quality and scintillation performance (light yield, scintillation decay times and the ratio of fast decay components). We generally discuss the composition dependence of defects and properties tailoring. We also performed the systematic comparative study with the stoichiometric LuAG:Ce,Mg ceramic and the commercial BGO and LuAG:Ce single crystals.

Ho:Lu3Al5O12(LuAG) transparent ceramics are potential 2 μm eye-safe laser materials. Polycrystalline 0.8 at.% Ho:LuAG ceramics with high optical quality were successfully fabricated by solid-state reactive sintering of high-purity oxide powders. The microstructure, the optical transmission, the spectrum characteristic, and the laser performance were investigated in this paper. The average grain size of Ho:LuAG ceramics vacuum sintered at 1830°C for 30 hour is about 14 μm. The in-line transmittance of the sample is measured to be 81.7% and 82.0% at 1000 and 2250 nm, respectively. The absorption and the emission cross sections are calculated to be 0.88 × 10−20 cm2 at 1906 nm and 1.26 × 10−20 cm2 at 2094 nm. Using a thulium-doped yttrium-lithium-fluoride (Tm:YLF) laser with the central wavelength of 1907.5 nm as the pump source, 2.67 W continuous wave (CW) laser operation at 2100.74 nm was obtained with a slope efficiency of 26.5%. The beam quality factor M2 was calculated to be 1.1, which indicated nearly diffraction-limited beam propagation and the laser was the fundamental TEM00 Gaussian mode.

In this paper, (Lu,Gd) 2 O 3 :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 Gd 2 O 3 incorporates well into the Lu 2 O 3 lattices and forms a solid solution. Particularly, strong red emission of 5 D 0 → 7 F 2 transition of Eu 3+ 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 Eu 3+ 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) 2 O 3 :Eu ceramic scintillators may have great potential in medical X-ray computed tomography (CT) due to their excellent properties.

Monovalent Li+ codoped Lu3Al5O12:Ce (LuAG:Ce) optical ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Optical absorption, radioluminescence spectra and scintillation properties such as light yield, scintillation decay times and afterglow were measured and compared with those of the Li+ free LuAG:Ce ceramic and the commercial LuAG:Ce single crystal samples. Positive effect of Li+ codopant consists mainly in the significant increase of scintillation light yield, acceleration of scintillation decay as well as the decrease of afterglow intensity. With 0.3% Li codoping, the obtained LuAG:Ce,Li ceramic displays a light yield of ∼29200 ph/MeV at 10 μs shaping time, higher than that of the LuAG:Ce single crystal and optical ceramic scintillators ever reported. The partial conversion of the stable Ce3+ to Ce4+ centers and the shallow and deep traps effect suppression by the Li+ codoping are discussed.

Lu3-xAl5O12:Ce optical ceramics (Lu(3-x)AG:Ce, x = 1, 2, 3 and 4 at.%, respectively) with Lu3+ compositions ranging from 1 to 4 at.% below stoichiometry content were fabricated by solid state reaction method and further optimized by an air-annealing process. The effect of Lu3+ deficiency on the optical, luminescence and scintillation properties of such a non-stoichiometric Lu3-xAl5O12:Ce ceramics was investigated. Significant influence in the material densification was found leading to strong changes in the transparency, radioluminescence (RL) and scintillation response of these ceramics. Within the range of 1 4 at.% Lu3+ deficiency, Lu-Al antisite defects were suppressed effectively and the Lu(3-x)AG:Ce ceramics displayed an extremely high RL intensity which reaches similar to 4 times higher than that of the latest commercial LuAG:Ce single crystals while its transparency deteriorated. The microstructure, presence of foreign phases and charge traps acting in scintillation mechanism were also Characterized by means of SEM, back scattered electron imaging and thermoluminescence techniques, respectively. (C) 2016 Elsevier B.V. All rights reserved.

Terbium aluminum garnet (Tb 3 Al 5 O 12 , TAG) transparent ceramics were fabricated by the solid-state reactive sintering of a mixture of commercial Tb 4 O 7 and α-Al 2 O 3 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.

The sintering behavior and doping concentration profile of the planar waveguide YAG/Nd:YAG/YAG ceramics by the tape casting and solid-state reaction method were investigated on the basis of densification trajectory, microstructure evolution, and Nd 3+ ions diffusion. The porosity of the green body by tape casting and cold isostatic pressing is about 38.6%. And the green bodies were consolidated from 1100 °C to 1800 °C for 0.5–20 h to study the densification and the doping diffusion behaviors. At the temperature higher than 1500 °C, pure YAG phase is formed, followed by the densification and grain growth process. With the increase of temperature, two sintering stages occur, corresponding to remarkable densification and significant grain growth, respectively. The mechanism controlling densification at 1550 °C is grain boundary diffusion. The diffusion of Nd 3+ ions is more sensitive to temperature than the sintering time, and the minimum temperature required for the obvious diffusion of Nd 3+ ions is higher than 1700 °C. Finally, planar waveguide YAG/1.5 at.%Nd:YAG/YAG transparent ceramics with in-line transmittance of 84.8% at 1064 nm were obtained by vacuum-sintering at 1780 °C for 30 h. The fluorescence lifetime of 4 F 3/2 state of Nd 3+ in the specimen is about 259 μs. The prepared ceramic waveguide was tested in a laser amplifier and the laser pulse was amplificated from 87 mJ to 238 mJ, with the pump energy of 680 mJ.

Cerium-doped lutetium aluminum garnet (LuAG:Ce) and yttrium aluminum garnet (YAG:Ce) transparent ceramics of same dimension were fabricated and their optical and scintillation properties were studied. LuAG:Ce transparent ceramic showed higher light yield under UV and X-ray excitation with respect to YAG:Ce transparent ceramic. YAG:Ce transparent ceramic showed higher light yield under gamma excitation and better energy resolution, which could be due to the considerable amount of slower emission (38.5%) in LuAG:Ce as well as lower optical transparency with respect to YAG:Ce ceramic.

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 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-Al 2 O 3 , Nd 2 O 3 and Y 2 O 3 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.

In this paper, a diode-pumped continuous-wave and passively Q-switched 1.06 μm laser with gain medium of ceramic was demonstrated. Laser output characteristics using Nd:YAG ceramics with different doping concentrations of 1.0%, 2.0%, and 4.0% were studied. A maximum output power of 7.74 W with optical efficiency of 51.6% was obtained through the optimization of the coupler's transmission. By using Cr 4+ :YAG crystals with initial transmissions of 80% and 90% as saturable absorbers, the pulsed ceramic Nd:YAG laser performance was investigated.

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 m 2 /W. The experimental results may provide design guidelines for the high power laser design and its applications.

La 0.2 Y 1.8 O 3 is a new and promising scintillator which is based on the host material without doping. Here the time gated X-ray excited optical luminescence is measured by using the excitation energy below, above and at the La L 3 -edge. A relatively slow and broad emission with peak at 415 nm has been observed as the dominant emission. Also, a weak emission at 360 nm is observed at the fast window, associated with the recombination of trapped excitons in Y 2 O 3 host. The observations show that the broad emission at 415 nm is most likely due to the recombination of trapped excitons associated with the La 3+ doping into Y 2 O 3 sites.

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%.

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 Cr 2+ :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 M 2 was 1.05, indicating nearly diffraction limited beam propagation.

We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y 2 O 3 –Al 2 O 3 –SiO 2 ) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y 3 Al 5 O 12 ) 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.

We demonstrated a diode-pumped-passively mode-locked laser based on a specially designed composite YAG/Yb:YAG ceramic. Theoretical studies reveal that this composite medium was beneficial for reducing the thermal effect. We obtained 1.35-ps pulses with a maximum output power of 475 mW based on an semiconductor saturable absorber mirror mode-locked laser at the room temperature of 22 °C. A maximum laser output power of 240 W was further generated using a master oscillator power amplifier system with the mode-locked YAG/Yb:YAG ceramic laser as the seeding oscillator.

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.

We demonstrated a high power acousto-optical Q-switched Ho:YAG ceramic laser operating at 2090.5 nm that was pumped at 1908 nm by a Tm:YLF laser. A maximum continuous wave power of 22.6 W was obtained, which corresponds to a slope efficiency of 50.6% and an optical-to-optical efficiency of 47.6% with respect to the absorbed pump power. For the Q-switched mode, to our best knowledge, the maximum average output power of 21.2 W was achieved with a minimum pulse width of 20 ns at a pulse repetition frequency of 10 kHz, corresponding to an energy of 2.12 mJ per pulse and a peak power of 106 kW.

Bi4Si3O12:Dy (BSO:Dy) crystals have been grown by the modified vertical Bridgeman method and doping effects on light yield have been investigated. Doped with small amount of Dy2O3 (0.05–0.3 mol%), the light yield and energy resolution of BSO crystals were improved significantly. However, high concentrations of Dy2O3 doping resulted in the decrease of light yield. Pulse height measurement under γ-ray irradiation shows that 0.1 mol% Dy2O3 doping can make the relative light yield of BSO from 24.6% to 35.8% of BGO crystal, with fast decay time of ~90 ns. X-ray excited radioluminescence spectra showed Dy doping has an extra emission in the host emission band (Bi3+ emission) and acts as a sensitizer to the Bi luminescent center. These results indicate that BSO:Dy crystal could be one of promising candidates for replacing BGO in some application such as electromagnetic calorimeter and dual readout in nuclear or high energy physics.