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To evaluate the diagnostic value of metagenomics next-generation sequencing (mNGS) in detecting pathogens in bronchoalveolar lavage fluid (BALF) for pulmonary infection in solid organ transplant patients in intensive care unit (ICU).A retrospective study was conducted, the BALF samples from 46 patients with post organ transplant pneumonia/suspected pneumonia admitted to the Department of Critical Care Medicine of the First Affiliated Hospital of University of Science and Technology of China from August 2018 to August 2021 were collected, all tested by simultaneous mNGS and conventional comprehensive microbial test (CMT), and the results of CMT were used as the reference standard to compare the differences in the diagnostic value of mNGS and CMT for pulmonary infections in solid organ transplant patients, and to analyze the diagnostic value of mNGS for mixed infections.(1) Pneumonia pathogens: a total of 31 pathogens were detected in 35 patients, including bacteria (16 species), fungi (9 species) and viruses (6 species). Among them, 25 pathogens were detected by mNGS and CMT, and only 19 pathogens were detected by mNGS. Among the microorganisms isolated by mNGS method, the detection rates of Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae were higher [51.4% (18/35), 42.9% (15/35), 31.4% (11/35), respectively]; Candida albicans, Aspergillus and Pneumocystis carinii were the most commonly detected fungi [31.4% (11/35), 22.9% (8/35), 22.9% (8/35), respectively]; 20 patients were positive for the virus, and the most commonly detected viruses were cytomegalovirus, herpesvirus and EB virus [28.6% (10/35), 20.0% (7/35), 17.1% (6/35), respectively]. In addition, one case of Brucella was detected by mNGS. (2) Diagnostic efficiency: as far as bacterial detection is concerned, 20 cases of negative results were obtained by CMT detection of 35 samples included in the study, and a total of 10 cases of positive results were obtained by mNGS detection of negative samples; the percentage of mNGS positive samples was significantly higher than that of CMT positive samples [odds ratio (OR) = 5.5, 95% confidence interval (95%CI) = 1.2-24.8, P = 0.02]. When compared with CMT, the sensitivity and specificity of mNGS were 93.3% and 50.0%, and the positive predictive value (PPV) and negative predictive value (NPV) were 58.3%, 91.1%. As far as fungal detection was concerned, there was no significant difference in the percentage of positive samples between the two methods (OR = 1.5, 95%CI = 0.5-4.2, P = 0.60); the sensitivity and specificity of mNGS were 72.2% and 64.7%, and the PPV and NPV were 68.4%, 68.8%; CMT test of the 35 included samples produced 17 negative results, and mNGS test of the negative samples produced 6 positive results. A total of 20 patients tested positive for the virus by mNGS. In addition, 23 patients (65.7%) were diagnosed with pulmonary mixed infection.The use of mNGS to detect pathogens in BALF can improve the sensitivity and specificity of bacterial identification of pulmonary infection in critically ill organ transplant patients, and mNGS has obvious advantages in detecting virus and identifying mixed infections.

In this paper, a combination active thermography and three-dimensional (3D) structural optical imaging is reported on the nondestructive inspection of curved clad composites with subsurface defects. Artificial points are marked on the background of test objective and helpful to obtain the mapping matrix from two-dimensional (2D) thermal wave characteristic imaging data to 3D spatial coordinate’s digital model. The 3D digital model is transformed into a new coordinate system and then reprojected onto the thermal-wave feature image exactly. The fusion of 2D thermal-wave characteristic data and the 3D digital model is achieved by bilinear interpolation. Specimens of carbon fiber reinforced polymer (CFRP) skin-honeycomb sandwich (CFRP-SHS) and High silicon oxygen phenolic resin (HSOPR) sheet with artificial defects are prepared for the experimental investigation. Experimental results indicate that the proposed method can reliably inspect the defects and accurately locate defect positions on the curved surface of CFRP-SHS and HSOPR laminate test sample, and it has a significantly potential for the use of aerospace and aircraft manufacturing and application.

Application of group decision making to practical environmental management problems indicates that effectively avoiding the loss of decision information and reasonably aggregating expert views are two main challenges during the decision-making process. Hence, this paper focuses on the utilization of interval-valued triangular fuzzy numbers for expressing expert opinions and the introduction of Group-G1 and Hamming-based weighted polymerization operator to incorporate the fuzzy information provided by individual experts, into group consensus opinion. The developed integrated fuzzy group decision-making framework was then applied to the evaluation and selection of the most desirable technology for removing low-concentration cadmium ions from water. It has been determined that hydroxide precipitation was the most preferred option at the current stage because of its relative simplicity and high maturity. However, the rankings generated based on expert opinions suggested that adsorption technologies, especially biosorption, could also be preferred because of its low-cost and environment-friendly characteristics. Finally, the reliability of the resulting priority-rankings was investigated by sensitivity analysis. The result showed this fuzzy group decision-making framework is potentially of great value for developing robust environmental recommendations and thus enables experts to make informed decisions and achieve optimal results.

Coexistence of heavy metals and endocrine disrupting compounds in polluted water with competitive adsorption behavior necessitates design of tailored adsorbents. In this work, β-cyclodextrin modified magnetic rice husk-derived cellulose (β-CD@MRHC) which can provide independent functional sites for effectively binding the above two types of contaminants was synthesized and used for Pb(II) and BPA elimination in both unit and multivariate systems. Characterizations results confirmed successful β-CD grafting and Fe

By grafting sulfur-bearing groups onto rice husk with magnesium xanthate, a novel biosorbent (RH-M) was synthesized for removal of cadmium from water. New sulfur containing binding sites were achieved efficiently according to Fourier Transform Infrared Spectroscopy and elemental analysis, and the alternation of surface morphology of RH-M was presented by Scanning Electron Microscopy. The adsorption performance of xanthate-modified biosorbent including adsorbent dosage effect, pH-dependence, kinetic curves and equilibrium isotherms were systematically investigated. The Cd(II) adsorption of RH-M was found to follow Langmuir isotherm model with maximum adsorption capacity of 137.16 mg g−1, significantly higher than that of many other reported adsorbents. The high-density sulfur-bearing groups on the functionalized rice husk surface are believed to improve the cadmium uptake due to a combination of ion exchange and chelation. Moreover, RH-M exhibited fast Cd(II) uptake ability in an exceptionally high correlation with pseudo-second-order kinetic model. Besides, Desorption experiments demonstrated that 0.5 M HNO3 solution could effectively desorb Cd(II) from the biosorbent with recovery rate up to 75% after four consecutive cycles. All these results recommend RH-M as a promising biosorbent for cadmium removal in aqueous solution.

Efficient isomerization of glucose into fructose contributes to the utilization of biomass producing 5-hydroxymethylfurfural (HMF). In this work, we have explored a novel catalyst for isomerization of glucose into fructose. By the mediation of polydopmaine (PDA), MnSn(OH)6 was formed on cryptomelane-type manganese oxide (OMS-2). The composite MnSn(OH)6/PDA@OMS-2 can efficiently catalyze the glucose isomerization to fructose, with a yield of fructose 47 ± 1.6%. When used together with the Bronsted acid catalyst Amberlyst-15, the HMF yield from glucose was 53 ± 2.5%. Consecutive use of the composite demonstrated that after eight cycles the activity can be retained in terms of the yield of fructose. The mechanism of polydopamine-mediated formation of MnSn(OH)6 has been investigated. The desired yield of fructose has been obtained by MnSn(OH)6/PDA@OMS-2, and the preparation of the catalyst has also shown advantages, including low cost and easy preparation, short preparation time (36 h), and low temperature (≤...

Due to the increasing number of unexpected water source pollution events, selection of the most appropriate disposal technology for a specific pollution scenario is of crucial importance to the security of urban water supplies. However, the formulation of the optimum option is considerably difficult owing to the substantial uncertainty of such accidents. In this research, a multi-stage technical screening and evaluation tool is proposed to determine the optimal technique scheme, considering the areas of pollutant elimination both in drinking water sources and water treatment plants. In stage 1, a CBR-based group decision tool was developed to screen available technologies for different scenarios. Then, the threat degree caused by the pollution was estimated in stage 2 using a threat evaluation system and was partitioned into four levels. For each threat level, a corresponding set of technique evaluation criteria weights was obtained using Group-G1. To identify the optimization alternatives corresponding to the different threat levels, an extension of TOPSIS, a multi-criteria interval-valued trapezoidal fuzzy decision making technique containing the four arrays of criteria weights, to a group decision environment was investigated in stage 3. The effectiveness of the developed tool was elaborated by two actual thallium-contaminated scenarios associated with different threat levels.

Because of the increasing frequency and intensity of unexpected natural disasters, providing safe drinking water for the affected population following a disaster has become a global challenge of growing concern. An onsite water supply technology that is portable, mobile, or modular is a more suitable and sustainable solution for the victims than transporting bottled water. In recent years, various water techniques, such as membrane-assisted technologies, have been proposed and successfully implemented in many places. Given the diversity of techniques available, the current challenge is how to scientifically identify the optimum options for different disaster scenarios. Hence, a fuzzy triangular-based multi-criteria, group decision-making tool was developed in this research. The approach was then applied to the selection of the most appropriate water technologies corresponding to the different emergency water supply scenarios. The results show this tool capable of facilitating scientific analysis in the evaluation and selection of emergency water technologies for enduring security drinking water supply in disaster relief.

Herein, microwave-functionalized cellulose derived from rice husk was cost-effectively prepared and employed for Pb(II), Cd(II) and Ni(II) elimination in mono- and multi-component systems. Benefiting from microwave irradiation, the functionalized process was achieved in 6.5 min and the resultant RHMW-X possessed remarkably high adsorption capacities of 295.20 mg/g for Pb(II), 151.51 mg/g for Cd(II) and 72.80 mg/g for Ni(II) within the equilibrium time of 30 min. Noticeably, the metal ions adsorption rate and capacity in binary and ternary systems were lower than that of unary systems. The coexistence of Cd(II) and Ni(II) significantly slowed down the Pb(II) adsorption in binary and ternary systems, while Pb(II) exhibited the most obvious influence on the metal ions uptake in the multi-component systems. FT-IR and XPS results revealed that both ion exchange and chelation were functioned in the metal ions uptake, while physical interaction was also involved in the adsorption process. Moreover, the RHMW-X possessed favorable recyclability with slight adsorption efficiency decline during five cycles in different systems. Particularly, the RHMW-X could effectively purify actual industrial wastewater containing Pb(II), Cd(II) and Ni(II) for meeting regulatory requirements. This work facilitates the omnidirectional improvement of adsorbents for the de-pollution of practical heavy metals wastewater.

Cadmium is highly poisonous to mammals and related water pollution incidents are increasing world-widely. Here, the clean-up of trace Cd(II) by a combined process of microwave-functionalized rice husk (RHMW-M) and poly aluminium chloride (PAC) was investigated for the first time, with the exploration of removal mechanism and efficacy. Microwave irradiation was found to be a new approach to achieve the functionalized procedure, which could decrease the processing time from 2.5 h to 390 s with the Cd(II) uptake of the outcome product soaring from 137.16 mg/g to 191.32 mg/g. The ultra-rapidly prepared RHMW-M exhibited a fast adsorption equilibrium within 30 min over a wide pH range of 5.0–8.0, and the FT-IR and XPS studies confirmed that both ion exchange and chelation were functioned in the Cd(II) uptake process. Controlled by the turbidity threshold of drinking water treatment plant, the feasible dosage of RHMW-M in the absence and presence of 30 mg/L PAC increased from 30 to 760 mg/L, which could effectively deal with the trace Cd(II) at the concentration from 33 μg/L up to 0.933 mg/L, exhibiting much better performance than traditional alkali precipitation. Predictably, this simple and scalable RHMW-M/PAC system could afford a promising end-of-pipe solution for heavy-metal contamination.

By means of creep property measurement and microstructure observation, an investigation has been made into microstructure and creep behavior of a directional solidification Ni-based superalloy at high temperatures. Results show that after full heat treatment, small cuboidal γ′ precipitates distribute in the dendrite regions, while coarser ones distribute in the inter-dendrite regions. In the primary stage of creep, the γ′ phase in alloy is transformed into the rafted structure along the direction vertical to stress axis, and then the creep of alloy enters the steady state stage. And dislocations slipping in the g matrix and climbing over the rafted γ′ phase are thought to be the deformation mechanism of the alloy during steady creep stage. At the latter stage of creep, the alternate slipping of dislocations may shear and twist the rafted γ′/γ phases, which promotes the initiation and propagation of the micro-cracks along the boundaries near the coarser rafted γ′ phase. And the bigger probability of the creep damage occurs in the grain boundaries along 45° angles relative to the stress axis due to them bearing relatively bigger shearing stress.

Pristine rice husk (RH), a kind of agricultural waste based biosorbent, was chemically modified by introducing sulfur-bearing groups with the CS2 treatment under caustic medium. Using response surface methodology (RSM), the interactive effects of three preparation variables on the cadmium uptake and material yield of xanthate-modified rick husk (RH-X) were investigated, and two quadratic regression models were developed to correlate the preparation parameters to the two responses. Through process optimization, the optimal RH-X was finally obtained under the optimum synthesis conditions (i.e., 1.00 CS2-RH ratio, 60.00 min xanthation contact time and 18.50 °C xanthation temperature), resulting in 138.85 mg g−1 of cadmium uptake, and 68.63% of RH-X yield, strictly similar to the values predicted from the models, with extremely small errors of 0.85 and 0.96%, respectively. Overall, cheap and abundant raw materials, low-cost and easily-controlled preparation and excellent cadmium adsorption ability can make RH-X a preferred biosorbent for wastewater decontamination.

By means of creep curves measurement and microstructure observation, an investigation has been made into the influence of the element Re on creep behaviors of single crystal nickel-base superalloy at intermediate temperature. Results show that, after fully heat treated, microstructure of the alloy consists of the cubic γ′ phase embedded coherent in the γ matrix. Comparing with Re-free superalloy, 4.5% Re alloy displays a better creep resistance and longer creep rupture life in the ranges of the applied stresses and temperatures. After crept for 425 h up to fracture at 760 °C/800 MPa, the γ′ phase in the alloy keeps still the regular cubical configuration, which is attributed to the effect of the element Re decreasing the diffusing rate of other elements during creep. The deformation features of the alloy during creep are that the dislocations move in the γ matrix channels and shear into the γ′ phase, the 〈110〉 super-dislocation shearing into the γ′ phase may be decomposed to form the configuration of (1/3)〈112〉 super-Shockleys partials plus the stacking fault, which may hinder dislocations movement and restrain the cross-slipping of dislocations. This is thought to be the main reason of the alloy having a better creep resistance. In the latter stage of creep, the crack is firstly initiated in the interface of γ′/γ phases and propagated along the interface vertical to the stress axis up to the occurrence of the creep fracture, which is thought to be the fracture mechanism of the alloy during creep.

China has suffered various water source pollution incidents in the past decades, which have resulted in severe threats to the safety of the water supply for millions of residents. From the aspects of quantity fluctuation, temporal volatility, regional inequality, pollutant category variation, and accident type differences, this study first characterizes the current status of water source contaminations in China by analyzing 340 pollution events for the period spanning from 1985 to 2013. The results show a general increase in the number of accidents during the period 1985–2006 and then a rapid decline starting in 2007. Spring and summer are high-incidence seasons for pollution, and the accident rate in developed southeastern coastal areas is far higher than that in the northwestern regions. Hazardous chemicals and petroleum are the most frequently occurring pollutants, whereas heavy metals and tailings are becoming emerging contaminants during occasional pollutions. Most of the accidents that occurred before 2005 were blamed on illegal emissions or traffic accidents; however, leakage in production has gradually become a major accident type in the past decade. Then, in combination with government actions and policy constraints, this paper explores the deep inducements and offers valuable insight into measures that should be taken to ensure future prevention and mitigation of emergent source water pollution.

Sudden water source pollution resulting from hazardous materials has gradually become a major threat to the safety of the urban water supply. Over the past years, various treatment techniques have been proposed for the removal of the pollutants to minimize the threat of such pollutions. Given the diversity of techniques available, the current challenge is how to scientifically select the most desirable alternative for different threat degrees. Therefore, a novel two-stage evaluation system was developed based on a circulation-correction improved Group-G1 method to determine the optimal emergency treatment technology scheme, considering the areas of contaminant elimination in both drinking water sources and water treatment plants. In stage 1, the threat degree caused by the pollution was predicted using a threat evaluation index system and was subdivided into four levels. Then, a technique evaluation index system containing four sets of criteria weights was constructed in stage 2 to obtain the optimum treatment schemes corresponding to the different threat levels. The applicability of the established evaluation system was tested by a practical cadmium-contaminated accident that occurred in 2012. The results show this system capable of facilitating scientific analysis in the evaluation and selection of emergency treatment technologies for drinking water source security.

We report on the experimental observation of dynamic behaviors in diode pumped passively Q-switched Nd:GdVO 4 and Nd:YVO 4 lasers. In addition to the period-doubling route to chaos, various periodic windows have also been observed. Based on an extended rate equation model the chaotic nature of the lasers is numerically simulated. It was found that under the experimental condition the model could qualitatively reproduce the experimental observations.

We report on a diode pumped passively Q-switched Nd:Gd 0.64 Y 0.36 VO 4 laser with a Cr 4+ :YAG saturable absorber. We show experimentally that by using an appropriately coated GaAs wafer as output coupler, the Q-switched pulse width can be significantly suppressed. Stable Q-switched pulse train with pulse width of 2.2 ns, peak power of 26.3 kW, repetition rate of 15.38 kHz have been obtained under an absorbed pump power of 8.54 W. The physical mechanism of pulse width narrowing by the GaAs wafer was also experimentally investigated.

A Nd0.0055(Gd0.64Y0.36)0.9945VO4 mixed laser crystal has been successfully grown by the Czochralski method. Properties of this crystal have been introduced. Formed with a simple concave-plano resonator, passive Q-switching operation of a diode-pumped Nd0.0055(Gd0.64Y0.36)0.9945VO4 laser with Cr4+:YAG has been demonstrated. For the Q-switched operation, the maximum average power was measured to be 1.11 W with a corresponding pulse repetition rate of 10 kHz and a Q-switched pulse duration of 7.6 ns. The largest single Q-switched pulse energy of 111 μJ and the highest peak power of 14.61 kW have been obtained in the laser.

We report on a diode-pumped passively mode-locked Nd:Gd0.64Y0.36VO4 laser with a Cr4+:YAG saturable absorber. Q-switched mode locking (QML) with 90% modulation depth was obtained. The peak power of the mode-locked pulse near the maximum of the Q-switched envelope was estimated to be about 1.7 MW at the pump power of 12 W. Besides QML, continuous-wave mode locking was also experimentally realized, for the first time to our knowledge, in the laser under a strong intracavity pulse energy fluence. The mode-locked pulse width is about 2.96 ps at a repetition rate of 161.3 MHz.

We report on the passively Q-switched mode-locking of a quasi-cw (QCW) diode pumped Nd:GdVO 4 laser with Cr 4+ :YAG saturable absorber. We show that by using the QCW pumping high quality Q-switched mode-locking can be easily obtained in the laser even with a simple two-mirror laser cavity configuration. Mode locked pulses with pulse width of about 1 ps at repetition rate variable from 500 MHz to 1 GHz has been obtained.

Trade records show that since the 1990s China has changed from a net exporting to a net importing country with respect to some species of snakes. Imports of snakes to China increased up to 2002, when the National Wildlife Management Authority imposed a suspension of international trade in snakes. We investigated the impact of the ban using the same methods as an earlier study of this trade for the period 1990–2001. We found that both imports and exports of snakes recorded in the CITES Trade Database and the Wild Animal and Plant International Trade Database of China have decreased markedly since 2004. The combination of national-level control measures and CITES regulations appear to have controlled the previously unsustainable utilization of snakes in China.

We report on a diode end-pumped passively mode-locked Nd:GdVO4 laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO4 laser using a GaAs wafer as the saturable absorber.

We have demonstrated a passively Q-switched operation of Nd:GdVO4 laser in which a GaAs crystal is used as the saturable absorber for the first time as far as we know. A maximum average output power of 1.64 W was obtained at an incident pump power of 12 W , the corresponding optical conversion efficiency and peak power were 13.7% and 116.8 W , respectively. The maximum peak energy obtained in the experiment by 50% transmission couple was 19 μJ .

We report on the experimental studies of diode-pumped Nd:GdVO 4 lasers passively Q-switched by Cr 4+ :YAG crystals of different initial transmission. Stable, high average power Q-switched pulses of duration of about 6 ns and peak power of 26.4 kW have been obtained. Passive Q-switched property of the laser under different Nd:GdVO 4 doping concentrations and saturable absorber initial transmissions are experimentally compared.

The thermal conductivities of Nd:YAG, M(Y,Gd)VO4 crystals were measured at 298 K. The value of Nd:GdVO4 crystal along direction was 11.4 W/mK, which was higher than that of YAG crystal measured to be 10.7 W/mK. The principal refractive indices of Nd:GdVO4 crystal in the temperature range from 20 °C to 170 °C were determined by auto-collimation method. Based on the measured values of refractive indices, the Sellmeier equation and expression of temperature dependence of refractive indices have been obtained. The measured results show that the birefringence Δn is 0.22007 at 20 °C and temperature coefficient of birefringence is 4.33 × 10−6/°C for 1.064 μm. These results prove that the GdVO4 crystal is a laser crystal with excellent thermal and birefringence properties. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Raman-scattering investigations in two crystals, Er:Yb:YCa4O(BO3)3 (EYYCOB) and Er:YCa4O(BO3)3 (EYCOB), show that the Yb3+ ions doped in the crystal largely change the crystal Raman spectra especially those of the Raman tensor elements αXX, αZZ, αXY, and αYZ, which imply the better nonlinear optical properties possible for this crystal as a nonlinear optical material, and these Yb3+ ions due to their influence on the symmetry of some Rare-earth (RE)-O octahedra also change their ligand field, which imply the better laser properties possible for this crystal as a laser material. These Raman measurements also show that the characteristic spectra of the crystals is mainly contributed by the BO3 triangles and partly by the Ca(1)O6 octahedra, which imply that the structural rigidity of the crystals is mainly ascribed to the BO bond stretching and bending and partly by the Ca(1)O bonds. On the basis of Judd–Ofelt theory, the effect of the sensitizing Yb3+ ions on the absorbance is analyse by comparing with the absorption spectra of EYYCOB and EYCOB. The spectral parameters around the pumping wavelength of an InGaAs diode laser and the luminescence parameters at about 1500 nm also are calculated for the crystal EYYCOB. These indicate that the crystal EYYCOB as a nonlinear optical and laser material would be excellent especially the radiation laser around 1500 nm to be desirable.

The crystal growth of vanadate crystals is realised. Nd:YVO 4 , Nd:GdVO 4 and Nd:Gd x La 1− x VO 4 ( x =0.80, 0.60, 0.45) are determined effective segregation coefficients and laser properties of these crystals. All the crystals have the zircon structure with the space group of I 4 1 /amd. We find the Nd:YVO 4 crystal is the easiest one to grow among these crystals, the laser and thermal properties of Nd:GdVO 4 are the best, and Nd:Gd x La 1− x VO 4 ( x =0.80, 0.60, 0.45) crystals are the most difficult to be grown among the vanadate crystals. Under the pumping power of a 3 W laser diode, output powers of 1.27 W at 1.06 μm and 800 mW at 1.34 μm for the Nd:GdVO 4 crystal, 1.14 W at 1.06 μm and 780 mW at 1.34 μm for the Nd:YVO 4 crystal, and 1.18 W at 1.06 μm and 671 mW at 1.34 μm for the Nd:Gd 0.8 La 0.2 VO 4 crystal were obtained, and intracavity frequency-doubling to 532 and 670 nm was also demonstrated using KTiOPO 4 and LiB 3 O 5 crystals.

A new liquid-phase method synthesizing Nd:GdVO 4 polycrystalline materials was introduced and excellent Nd:GdVO 4 single crystals were successfully grown by the Czochralski method. The effective segregation coefficients of Nd ion in Nd:GdVO 4 crystal were determined. The main defects and the methods of reducing them have been discussed. The fluorescence lifetimes of different Nd ions in crystal were also measured and found the crystal had obvious concentration quenching effect. In the field of high power laser system, a maximum laser output of 14.5 W at 1.06 μm was obtained, and the optical conversion efficiency is 63.0%. Up to 4.93 W laser output at 1.34 μm was also achieved with slope efficiency of 33.3%.

LD-pumped actively Q-switched intracavity frequency-doubled Nd:GdVO4/KTP red laser has been introduced. A maximum red average output power of 0.78 W at 671 nm was obtained at pulse-repetition frequency (PRF) of 15 kHz and the optical conversion efficiency was 6.5%. At the incident pump power of 12 W , the shortest laser pulse occurred at PRF of 15 kHz . Its full-width at half-maximum and the highest peak power were measured to be 35.8 ns and 3.38 kW . The largest single pulse energy of 56.3 μJ was achieved at PRF of 10 kHz . The influence factors on the Q-switched Nd:GdVO4/KTP red laser have been discussed.

Different Gd/Y polycrystalline materials were synthesized by a liquid-phase reaction method and several Nd:YGdVO 4 crystals with low Nd ion concentrations were successfully grown by the Czochralski method. A component analysis was made and the absorption, emission spectra had been measured. The influence of different Gd/Y ratios on the laser properties was also investigated for the first time. The laser experiments have proved that Nd:YGdVO 4 crystals are good laser materials.

A diode-pumped 1.34 μm Nd:GdVO4 laser operating in cw and active Q-switching modes has been demonstrated. 4.15 W of cw output power was obtained at the highest attainable pump power of 12.3 W, resulting in an optical conversion efficiency of 33.7%, the slope efficiency was determined to be 37.6%. In Q-switching operation, a maximum average output power of 2.7 W was generated at pulse repetition frequency (PRF) of 50 kHz, with an optical conversion efficiency of 22% and a slope efficiency of 29.2%. The laser pulses with shortest duration, highest energy and peak power were achieved at PRF of 10 kHz, the parameters being 15 ns, 160 μJ, and 10.7 kW, respectively. By intracavity frequency-doubling with a type II phased-matched KTP crystal, 0.62 W average power at 0.67 μm was produced at a PRF of 15 kHz, the resulting pulse energy, peak power, and pulse width being 41.3 μJ, 2.2 kW, and 19 ns, respectively. A group of analytical formulae, based on rate equations, are presented to evaluate the operational parameters of an actively Q-switched laser. Calculated results were found to be in close consistency with the experimental data.

The laser outputs of 1.26, 0.95, 0.5 and 0.32 at% Nd-doped concentrations in Nd:YVO 4 crystal samples were performed under high pumping power of laser diode. The reason of different Nd-doped concentrations in Nd:YVO 4 crystals influencing on the laser output properties was explained. The intracavity double frequency laser outputs of Nd:YVO 4 crystal at 532 and 671 nm were also performed. Our experimental results show that the optimum Nd-doped concentration in Nd:YVO 4 crystal is about 0.5 at% under a pumping power of 30 W.

We demonstrated a diode-end-pumped continuous-wave and passively Q-switched Nd:GdVO 4 laser operating at 1.06 μm wavelength with a three-mirror folded resonator. The maximum continuous-wave output power of 8.18 W was obtained at the incident pump power of 22.5 W , with the corresponding optical conversion efficiency of 36.4%. For Q-switched operation, the maximum average output power was measured to be 4.64 W with the corresponding optical conversion efficiency of 25.8%, when the initial transmission of Cr 4+ :YAG crystal was 90%. The shortest pulse width of 83 ns , the largest pulse energy of 20.7 μJ and the highest peak power of 246.7 W were obtained when the Cr 4+ :YAG crystal with an initial transmission of 85% was used.

A diode-end-pumped high-power Nd:GdVO 4 laser operating at 1.34 μm has been demonstrated. The maximum continuous-wave output power of 4.62 W was obtained at the incident pump power of 14.75 W, with the corresponding optical conversion efficiency of 31.3% and the average slope efficiency of 33.1%. By using the experimentally measured threshold pump power and slope efficiency, the stimulated emission cross-section of Nd:GdVO 4 crystal at 1.34 μm was determined to be 1.78×10 −19 cm 2 .

A new liquid-phase method synthesizing Nd:GdVO 4 polycrystalline materials was introduced. High optical quality Nd:GdVO 4 single crystals have been successfully grown by the Czochralski method. The effective segregation coefficients of Nd ion in Nd:GdVO 4 crystal have been measured and discussed. Laser outputs at 1.06 μm and at 1.34 μm were achieved when Nd:GdVO 4 crystal samples of 0.52 at% Nd concentration were pumped by a high-power LD. A maximum output of 14.5 W at 1.06 μm has been obtained when the pump power is to 26 W, giving the slope efficiency of 63%. It is reported the first time that up to 4.64 W power laser at 1.34 μm has been achieved with optical conversion efficiency of 31.4% and slope efficiency of 32.9%.

Polycrystalline materials were synthesized by liquid-phase reaction method and several excellent Nd:GdVO 4 crystals with different concentrations of Nd were successfully grown by the Czochralski method with strict growth control. It is found that the effective segregation coefficient of Nd ion in Nd:GdVO 4 crystal decreases with the increase of Nd concentration at the same pulling rate and rotation rate. The defects in Nd:GdVO 4 crystals were investigated by metallurgical microscope and chemical etching. The etch figures on (1 0 0) (0 1 0) (0 0 1) planes were observed. Rectangular-shaped etch pits on the (1 0 0) and (0 1 0) planes were found but those found on the (0 0 1) plane were square. The main defects found were dislocations, sub-grain boundaries, step faceting, inclusions, color centers, scattering and methods of reducing them have also been discussed.

Laser emission at 1.55 μm has been achieved for the novel laser-nonlinear optical crystal Er:Yb:YCa 4 O(BO 3 ) 3 operated at room temperature, and pumped by a 976 nm diode. A tunable range of 23 nm (1535–1558 nm) was realized with a 50 μm etalon.

In this paper, series crystals Nd:Gd0.8La0.2VO4, Nd:Gd0.6La0.4VO4, and Nd:Gd0.45La0.55VO4 were grown by the Czochralski method. The structure and lattice constants of the series crystals were measured. The morphology of Nd:Gd0.8La0.2VO4 is discussed, and it is composed of {100} and {101} simple forms. The thermal expansion and specific heat of the Nd:Gd0.8La0.2VO4 crystal were also measured. The absorption and emission spectra of the Nd:Gd0.8La0.2VO4 and Nd:Gd0.6La0.4VO4 crystals were measured at room temperature. The laser outputs at 1.06 and 1.34 μm were determined when a crystal sample of Nd:Gd0.8La0.2VO4 was pumped by a laser diode at 808 nm, and the visible green and red laser outputs of the intracavity frequency double at 0.53 and 0.67 μm were determined when nonlinear KTiOPO4 and LiB3O5 crystals were used.

The polarised absorption and fluorescence spectra of Nd:Gd0.8La0.2VO4 crystal are measured and compared to those of Nd:GdVO4. CW laser properties of diode-pumped Nd:Gd0.8La0.2VO4 crystal operating at fundamental wavelengths of 1.06 and 1.34 μm , as well as when intracavity frequency-doubled to 532 and 670 nm , have been studied. The maximum output powers at 1.06 μm , 1.34 μm , 532 nm and 670 nm are 1.18 W , 671 mW , 206 mW and 42 mW respectively, at a diode-launched pump power of 2.9 W . The threshold pump powers are 80, 267, 7 and 15 mW respectively.

A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd : GdVO 4 / KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W , the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns , yielding the highest peak power of 7.44 kW ; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz .

An end-pumped acousto-optically Q-switched Nd:GdVO 4 laser has been demonstrated, from which 7.25 W average output power at 1.06 μm at pulse repetition frequency (PRF) of 60 kHz was obtained with an optical conversion efficiency of 38.1% and an averaged slope efficiency of 43.5%. At incident pump power of 17 W, the highest single pulse energy and peak power were achieved when the laser was operated at a PRF of 10 kHz, and were determined to be 340 μJ and 26.2 kW, respectively. The shortest laser pulse with FWHM width of 11 ns was observed at PRF of 20 kHz. Through intracavity frequency doubling, we obtained 2.18 W average green output power with pulse width of 45 ns at a PRF of 25 kHz, the corresponding optical conversion efficiency was 21.8%, and the resulting single pulse energy and peak power were determined to be 87.2 μJ and 1.94 kW, respectively. The results of theoretical calculations on the basis of rate equations are also presented, showing close consistency with the experimental data.

The absorption properties of Nd:YVO4 crystals with various doping levels and lengths are reported. The effective stimulated emission cross-sections of different doping levels are calculated with measured upper-level lifetimes. Our investigation gives good advice on the optimization of LD end-pumped Nd:YVO4 laser.

A diode-laser-array end-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO4/KTP green laser, formed with a three-mirror folded resonator, has been demonstrated. With 15 W of pump power incident upon the Nd:GdVO4 crystal, a maximum average green output power of 3.75 W was obtained at 50 kHz of pulse repetition frequency, giving an optical conversion efficiency of 25%, whereas the effective intracavity frequency-doubling efficiency was determined to be 72%. At the incident pump power of 12.8 W, the shortest laser pulse was achieved at a pulse repetition rate of 10 kHz, the resulting pulse width, single pulse energy, and peak power were measured to be 35 ns, 108 μJ, and 3.1 kW, respectively.

In this paper, highly Yb-doped Ca 4 GdO(BO 3 ) 3 (Yb : GdCOB) crystals were grown by the Czochralski method. The absorption and fluorescence spectra were measured. The laser of Yb : GdCOB crystal was demonstrated with different output mirrors when it was pumped by a fiber-coupled laser diode (LD) at the wavelength of 976.4 nm. The lowest pumping threshold was 280 mW, the highest light–light conversion efficiency was 33.8%, and the highest slope efficiency up to 70% was thus calculated from the linear part of the curve. The self-frequency doubling (SFD) green laser output was also observed.

Nd : Ca 4 YO(BO 3 ) 3 (Nd : YCOB) and Nd : Ca 4 GdO(BO 3 ) 3 (Nd : GdCOB) crystals were grown by Czochralski method. Thermal expansion and specific heat of these two crystals were experimentally determined. Their fluorescence spectra were measured within the range from 1000 to 1500 nm. Laser output experiments at 1.06 and 1.33 μm of Nd : YCOB and Nd : GdCOB crystals were performed with a cw Ti : sapphire laser as the pump source.

In this paper, Er : Ca 4 YO(BO 3 ) 3 (Er : YCOB) and Er : Yb : Ca 4 YO(BO 3 ) 3 (Er : Yb : YCOB) crystals with large size and excellent quality have been grown by the Czochralski method. The absorption and emission spectra of Er : YCOB and Er : Yb : YCOB crystals have been measured; the emission spectrum of Er : Yb : YCOB crystal shows that the strongest emission peak is located at 1537 nm. An output power of about 2 mW at the wavelength of 1553 nm has been obtained under the pumping power of a fiber-coupled laser diode (LD) of 1600 mW at 976 nm, using a Y direction cut 2.5 mm thick Er : Yb : YCOB crystal sample.