Transition intensity calculation of Yb:YAG

The Yb：YAG is an excellent high-average power and ultra-short pulse laser crystal. Transition intensity parameters A（tp）~k and Huang–Rhys factors are fitted to its emission spectrum by the full-profile fitting method. Calculated results indicate that the emission spectrum of Yb：YAG at cryogenic temperature consists of three pure electron state transitions and two phononassisted transitions, one vibronic transition releases one-phonon of 3 cm^（-1）, and the other vibronic transition absorbs onephonon of 22 cm^（-1）. At 300 K, the phonon assisted transition of 3 cm^（-1） turns into two-or more-phonon assisted transitions.The procedure absorbing phonon can reduce the thermal load of Yb：YAG and improve the laser efficiency, which may be one of the reasons why Yb：YAG has excellent performance. The emission bands of Yb：YAG are broadened thermally, and the peak values decrease by several times. The emission cross sections of Yb：YAG determined by Fuchtbauer–Ladenburg（F–L） formula are remarkably different from those calculated with A（tp）~k, which indicates that it is necessary for a laser material to determine its transition intensity parameters A（tp）~kin order to reasonably evaluate the laser performance.

Optical parameters and energy levels splitting of Ho^(3+) in Ho^(3+): GdVO_4

Ho^3＋ ： GdVO4 is a new laser material suitable for high-power laser systems. In this paper we measure the absorption spectra of Ho^3＋ in the sample Ho^3＋： GdVO4. The intensity parameters are calculated by using the Judd-Ofelt theory. Some predicted spectroscopic parameters, such as the spontaneous radiative transition rate, branching ratio and integrated emission cross section are dealt with. And we also compare the optical parameters with those of other materials. From these results, it is found that there are many transitions which have large oscillator strengths and large integrated emission cross sections. Especially the transitions such as ^5 F4 → ^5 I 8, ^5 S2→^5 I8, ^5 F5 → ^5 I8 and ^5 I7 →^ 5 I8 are useful in solid-state lasers and other fields. Finally, we discuss the splitting of the energy levels of Ho^3＋ in the crystal GdVO4 based on the group theory.

Altitude and intensity characteristics of parametric instability excited by an HF pump wave near the fifth electron harmonic

An ionospheric heating experiment involving an O mode pump wave was carried out at European Incoherent Scatter Scientific Association site in Troms？. The observation of the ultra high frequency radar illustrates the systematic variations of the enhanced ion line and plasma line in altitude and intensity as a function of the pump frequency. The analysis shows that those altitude variations are due to the thermal effect, and the intensity variations of the enhanced ion line are dependent on whether or not the enhanced ion acoustic wave satisfy the Bragg condition of radar. Moreover, a prediction that if the enhancement in electron temperature is suppressed,those systematic variations will be absent, is given.

The influence of cation additives on the NIR luminescence intensity of Er^(3+)-doped borate glasses

Er3+-doped 25BaO-(25-x)SiO2-xAl2O3-25B2O3 transparent glasses are prepared with x = 0,12.5 and 25 by a solid-state reaction.The Er-related NIR luminescence intensity,which corresponds to the transition of 4I15/2-4I13/2,is obviously altered with different silicon/aluminum ratios.The Judd-Ofelt parameters of the Er3+ ions are adopted to explain the intensity change in the NIR fluorescence,and the Raman scattering intensity versus the amount of Al and/or Si components are discussed.The spectra of the three samples are quite similar in the peak positions,but different in intensity.The maximal phonon density of state for the samples is calculated from the Raman spectra and is correlated to the NIR luminescence efficiency.

Properties of Local Structure Surrounding Eu^(3+)Ion in Various Niobate-Silicate Glasses

A Series of niobate silicate glasses doped with Eu 3+ ions were prepared. The emission, phonon side band spectra, fluorescence line narrowing spectroscopy and fluorescence lifetimes in these glasses were studied. The intensity parameters and crystal field parameter of Eu 3+ were obtained. The results indicate that the intensity ratio of the electric dipole to magnetic dipole transition and the intensity parameter Ω 2 increase with the increasing concentration of Nb 2O 5, indicating that the symmetry becomes lower, the Eu O bonds become stronger and the covalency of Eu O bond increases. The value of B 20 decreases with the increasing concentration of Nb 2O 5, indicating that the distance between the Eu 3+ ion and oxygen decreases and the Eu O bond becomes strong, corresponding to the results of the former. As the concentration of Nb 2O 5 increases, the electron phonon coupling becomes stronger, thus the nonradiative transition rate of 5D 0 becomes larger and the lifetime of 5D 0 becomes shorter.

Judd-Ofelt parameters of the up-conversion phosphors： Er3＋ doped BaGd2ZnO5/PMMA and NaYF4/PMMA

We proposed a new approach to determination of Judd-Ofelt intensity parameters of Er^（3＋） doped phosphors via their absorption spectra. To validate this approach, JO parameters of Er^（3＋） doped Ba BaGd_2ZnO_5/PMMA and NaYF_4/PMMA composites were calculated and in a good agreement with the other glass and crystal. The spontaneous radiative transition probability, branching ratio, and radiative lifetime of the optical transitions were calculated by using the Judd-Ofelt theory. Intense near-infrared emission at 1553 nm was observed under 980 nm laser diode excitation at room temperature. The samples possessing high full-width at half-maximum reach 85 nm have potential application in broadband optical amplifier.

Association between ICU quality and in-hospital mortality of V-V ECMO-supported patients—the ECMO quality improvement action(EQIA)study:a national cohort study in China from 2017 to 2019

This cohort study was performed to explore the influence of intensive care unit(ICU)quality on in-hospital mortality of veno-venous(V-V)extracorporeal membrane oxygenation(ECMO)-supported patients in China.The study involved all V-V ECMO-supported patients in 318 of 1700 tertiary hospitals from 2017 to 2019,using data from the National Clinical Improvement System and China National Critical Care Quality Control Center.ICU quality was assessed by quality control indicators and capacity parameters.Among the 2563 V-V ECMO-supported patients in 318 hospitals,a significant correlation was found between ECMO-related complications and prognosis.The reintubation rate within 48 hours after extubation and the total ICU mortality rate were independent risk factors for higher in-hospital mortality of V-V ECMO-supported patients(cutoff:1.5%and 7.0%;95%confidence interval:1.05–1.48 and 1.04–1.45;odds ratios:1.25 and 1.23;P=0.012 and P=0.015,respectively).Meanwhile,the V-V ECMO center volume was a protective factor(cutoff of≥50 cases within the 3-year study period;95%confidence interval:0.57–0.83,odds ratio:0.69,P=0.0001).The subgroup analysis of 864 patients in 11 high-volume centers further strengthened these findings.Thus,ICU quality may play an important role in improving the prognosis of V-V ECMO-supported patients.