In this paper, optical spectra of LiYF4 single crystals doped with Tm3+ ions of various concentrations are reported. The emission intensity at 1.8 ktm first increases with increasing Tm3+ concentration, and reaches ...In this paper, optical spectra of LiYF4 single crystals doped with Tm3+ ions of various concentrations are reported. The emission intensity at 1.8 ktm first increases with increasing Tm3+ concentration, and reaches a maximum value when the concentration of Tm3+ is about 1.28 mol%, then it decreases rapidly as the concentration of Tm3+ further increases to 3.49 mol%. The emission lifetime at 1.8 p.m also shows a similar tendency to the emission intensity. The maximum lifetime of 1.8 μm is measured to be 17.68 ms for the sample doped with Tm3+ of 1.28 mol%. The emission cross section of 3F4 level is calculated. The maximum reaches 3.76 × 10 -21 cm2 at 1909 nm. The cross relaxation (3H6, 3H4 →3 F4, 3F4) between Tm3+ ions and the concentration quenching effect are mainly attributed to the change of emission with Tm3+ concentration. The largest quantum efficiency between Tm3+ ions is estimated to be ,-147% from the measured lifetime and calculated radiative lifetime. All the results suggest that the Tm3+/LiYF4 single crystal may have potential applications in 2 μm mid-infrared lasers.展开更多
Ho3+/yb3+ co-doped LiYF4 single crystals with various Yb3+ concentrations and ,-~ 0.98 mol% Ho3+ concentration are grown by the Bridgman method under the conditions of taking LiF and YF3 as raw materials and a tem...Ho3+/yb3+ co-doped LiYF4 single crystals with various Yb3+ concentrations and ,-~ 0.98 mol% Ho3+ concentration are grown by the Bridgman method under the conditions of taking LiF and YF3 as raw materials and a temperature gradient (40 ~C/cm-50 ~C/cm) for the solid-liquid interface. The luminescent performances of the crystals are investigated through emission spectra, infrared transmittance spectrum, emission cross section, and decay curves under excitation by 980 nm. Compared with the Ho3+ single-doped LiYF4 crystal, the Ho3+/yb3+ co-doped tiYf4 single crystal has an obviously enhanced emission band from 1850 nm to 2150 nm observed when excited by a 980-nm diode laser. The energy transfer from Yb3+ to Ho3+ and the optimum fluorescence emission around 2.0 p-m of Ho3+ ions are investigated. The maximum emission cross section of the above sample at 2.0 p.m is calculated to be 1.08 × 10-20 cm2 for the LiYF4 single crystal of 1-mol% Ho3+ and 6-mo1% Yb3+ according to the measured absorption spectrum. The high energy transfer efficiency of 88.9% from Yb3+ to Ho3+ ion in the sample co-doped by Ho3+ (1 mol%) and Yb3+ (8 tool%) demonstrates that the Yb3+ ions can efficiently sensitize the Ho3+ ions.展开更多
The vacuum ultraviolet (VUV) spectroscopic properties of praseodymium (Pr3+, 1at%) doped LaF3 nanocrystals/glass at room temperature and 20 K are reported. Two types of Pr3+ ions, those in LaF3 nanocrystals and those ...The vacuum ultraviolet (VUV) spectroscopic properties of praseodymium (Pr3+, 1at%) doped LaF3 nanocrystals/glass at room temperature and 20 K are reported. Two types of Pr3+ ions, those in LaF3 nanocrystals and those in the glass host, were excited to 4f 5d band by VUV using synchrotron radiation as an excitation source, and emissions of 1S0 → 1D2 (336 nm), 1S0 → 1I6 (397 nm ) of Pr3+ in the nanocrystals and emissions of 4f 5d → 3HJ, 3FJ of Pr3+ in the glass appeared at the same time. But unlike in the bulk sample crystals, emission of 3P0 → 3HJ, 3FJ as the second step of the quantum splitting (QS) of Pr3+ in the LaF3 nanocrystals was not observed at room temperature, which could be explained that Pr3+ ions in the glass absorbed the energy of 3P0 → 3H4 of Pr3+ in the nanocrystals. Two types of excitation spectra monitoring different emissions were also measured, so it could be observed that the lowest energy of 4f 5d band of Pr3+ in the nanocrystals was about 53 500 cm-1 (186 nm) and in the glass about 33 800 cm-1(295 nm), respectively. These emission and excitation spectra were contrasted to those of bulk sample crystals LaF3∶Pr3+.展开更多
A Dy3+-doped LiYF4 single crystal capable of generating white light by simultaneous blue and yellow light emission of phosphorescent centers is produced. Chromaticity coordinates and photoluminescence intensity vary ...A Dy3+-doped LiYF4 single crystal capable of generating white light by simultaneous blue and yellow light emission of phosphorescent centers is produced. Chromaticity coordinates and photoluminescence intensity vary with excitation wavelength. Under 350, 365, and 388 nm excitation, the crystal shows excellent white light emission. The most efficient wavelength for white light is 388 nm. The CIE coordina.tes are x=0.316 and y =0.321, and the color temperature (Tc) is 6 368 K. These results indicate that the studied crystal is a potential candidate for ultraviolet light-excited white light-emitting diodes.展开更多
The LiYF4 single crystals singly doped Ho3+ and co-doped Ho3+, Pr3+ ions were grown by a modified Bridgman method. The Judd-Ofelt strength parameters (Ω2, Ω4, Ω6) of No3+ were calculated according to the abso...The LiYF4 single crystals singly doped Ho3+ and co-doped Ho3+, Pr3+ ions were grown by a modified Bridgman method. The Judd-Ofelt strength parameters (Ω2, Ω4, Ω6) of No3+ were calculated according to the absorption spectra and the Judd-Ofelt theory, by which the radiative transition probabilities (A), fluorescence branching ratios (β) and radiative lifetime (τ rad) were obtained. The radiative lifetimes of 5/6 and 5/7 levels in Ho3+ (1 mol%):LiYF4 are 10.89 and 20.19 ms, respectively, while 9.77 and 18.50 ms in Ho3+/pr3+ doped crystals. Hence, the τ rad of 5/7 level decreases significantly by introduction of Pr3+ into Ho3+:LiYF4 crystal which is beneficial to the emission of 2.9 μm. The maximum emission cross section of Ho3+:LiYF4 crystal located at 2.05 μm calculated by McCumber theory is 0.51 ×10-20 cm2 which is compared with other crystals. The maximum emission cross section at 2948 nm in Ho3+/pr3+ co-doped LiYF4 crystal obtained by Fuchtbauer- Ladenburg theory is 0.68 × 10-20 cm2, and is larger than the value of 0.53 × 10-20 cm2 in Ho3+ singly doped LiYF4 crystal. Based on the absorption and emission cross section spectra, the gain cross section spectra were calculated. In the Ho3- ions singly doped LiYF4 crystal, the gain cross sections for 2.05 μm infrared emission becomes positive once the population inversion level reaches 30%. It means that the pump threshold for obtaining 2.05 μm laser is probably lower which is an advantage for Ho3+-doped LiYF4 2.05 μm infrared lasers. The calculated gain cross section for 2.9 μm mid-infrared emission does not become positive until the population inversion level reaches 40% in Ho3+/pr3+:LiYF4 crystal, but 50% in Ho3+ singly doped LiYF4 crystal, indicating that a low pumping threshold is achieved for the H03+:5/6 → 5/7 laser operation with the introduction of Pr3+ ions. It was also demonstrated that Pr3+ ion can deplete rapidly the lower laser Ho3+:5/7 level and has influence on the Ho3+:5/6 level. The Ho3+/pr3+:LiYF4 crystal may be a potential media for 2.9 μm mid-infrared laser.展开更多
The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is propo...The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is proposed.展开更多
The LiYF4 single crystal codoped with thulium and holmium ions was successfully grown by the Cz method. The optimal technical parameters obtained were as follows: the pulling rate was 0.16 mm/h; the rotation speed wa...The LiYF4 single crystal codoped with thulium and holmium ions was successfully grown by the Cz method. The optimal technical parameters obtained were as follows: the pulling rate was 0.16 mm/h; the rotation speed was 3 rpm; the cooling rate was 15 °C/h. The result of XRD curve showed that as-grown Tm,Ho:LiYF4 laser crystal belonged to the monoclinic system with scheelite-type structure and space group I41/a. The cell parameters calculated were: a=0.52160 nm, c=1.09841 nm and Z=4. Absorption and fluorescence spectra of Tm,Ho:LiYF4 laser crystal at room temperature were measured and analysed. The absorption cross section, FWHM and absorption coefficient at 779.3 nm calculated were 7.44×10–21 cm2, 8.7 nm and 2.23 cm–1, respectively. An intensive fluorescence emission peak appeared near 2045 nm. The emission cross section and fluorescence lifetime were 0.87×10–20 cm2 and 10.8 ms, respectively. The ratio of Tm–Ho transfer to its back-transfer process was 10.6.展开更多
Mid-infrared(MIR) emissions of 2.4 and 3.5 μm from Tm3+:LiYF4 single crystals attributed to3H4 →3H5 and3H5 →3F4 transitions as well as MIR emissions of 4.2,4.3,and 4.5 μm from Nd3+:LiYF4 lasers attributed to...Mid-infrared(MIR) emissions of 2.4 and 3.5 μm from Tm3+:LiYF4 single crystals attributed to3H4 →3H5 and3H5 →3F4 transitions as well as MIR emissions of 4.2,4.3,and 4.5 μm from Nd3+:LiYF4 lasers attributed to4I15/2 →4I13/2,4I13/2 →4I11/2,and4I11/2 →4I9/2 transitions,respectively,are observed.LiYF4 single crystals possess high transmittance of over 85% in the 2.5-6 μm range.The large emission crosssections of Tm-doped crystals at 2.4 μm(1.9×10-20cm2) and Nd-doped crystals at 4.2 μm(0.84×10-20 cm2) as well as the high rare-earth doping concentrations,excellent optical transmission,and chemicalphysical properties of the resultant samples indicate that Nd3+and Tm3+singly doped crystals may be promising materials for application in MIR lasers.展开更多
The 4f-5d transitions of Er3+ ions doped in crystals were widely studi ed due to their potential applications in quantum cutting phosphors and VUV lase rs,etc.The theory to do the calculations of 4f-5d transitions and...The 4f-5d transitions of Er3+ ions doped in crystals were widely studi ed due to their potential applications in quantum cutting phosphors and VUV lase rs,etc.The theory to do the calculations of 4f-5d transitions and various rela ted aspects,such as the ways to determining various parameters,were summarized .The impacts of various interactions on the spectra were also demonstrated clea rly with Er3+ ions in crystals CaF2 and LiYF4.Predicted results were compared w ith measured spectra.展开更多
Based on the completely parametric crystal-field model, the energy level parameters, including free-ion parameters and crystal-field parameters, obtained by fitting the experimental energy level data sets of Ln^(3+...Based on the completely parametric crystal-field model, the energy level parameters, including free-ion parameters and crystal-field parameters, obtained by fitting the experimental energy level data sets of Ln^(3+) in LiYF_4 were systematically analyzed. The results revealed that the regular variation trends of the major parameters at relatively low site symmetry still existed. The g factors of ground states were calculated using the parameters obtained from least-squares fitting. The results for Ce^(3+), Nd^(3+), Sm^(3+), Dy^(3+) and Yb^(3+) were in good agreement with experiment, while those of Er^(3+) deviated from experiment dramatically. Further study showed that the g factors depended strongly on B_4~6, and a slightly different B_4~6 value of -580cm^(-1) led to g factors agreeing well with the experimental values.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472125 and 51272109)the Natural Science Foundation of Ningbo City,China(Grant No.201401A6105016)K.C.Wong Magna Fund in Ningbo University,China(Grant No.NBUWC001)
文摘In this paper, optical spectra of LiYF4 single crystals doped with Tm3+ ions of various concentrations are reported. The emission intensity at 1.8 ktm first increases with increasing Tm3+ concentration, and reaches a maximum value when the concentration of Tm3+ is about 1.28 mol%, then it decreases rapidly as the concentration of Tm3+ further increases to 3.49 mol%. The emission lifetime at 1.8 p.m also shows a similar tendency to the emission intensity. The maximum lifetime of 1.8 μm is measured to be 17.68 ms for the sample doped with Tm3+ of 1.28 mol%. The emission cross section of 3F4 level is calculated. The maximum reaches 3.76 × 10 -21 cm2 at 1909 nm. The cross relaxation (3H6, 3H4 →3 F4, 3F4) between Tm3+ ions and the concentration quenching effect are mainly attributed to the change of emission with Tm3+ concentration. The largest quantum efficiency between Tm3+ ions is estimated to be ,-147% from the measured lifetime and calculated radiative lifetime. All the results suggest that the Tm3+/LiYF4 single crystal may have potential applications in 2 μm mid-infrared lasers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472125 and 51272109)the K.C.Wong Magna Fund in Ningbo University,China(Grant No.NBUWC001)
文摘Ho3+/yb3+ co-doped LiYF4 single crystals with various Yb3+ concentrations and ,-~ 0.98 mol% Ho3+ concentration are grown by the Bridgman method under the conditions of taking LiF and YF3 as raw materials and a temperature gradient (40 ~C/cm-50 ~C/cm) for the solid-liquid interface. The luminescent performances of the crystals are investigated through emission spectra, infrared transmittance spectrum, emission cross section, and decay curves under excitation by 980 nm. Compared with the Ho3+ single-doped LiYF4 crystal, the Ho3+/yb3+ co-doped tiYf4 single crystal has an obviously enhanced emission band from 1850 nm to 2150 nm observed when excited by a 980-nm diode laser. The energy transfer from Yb3+ to Ho3+ and the optimum fluorescence emission around 2.0 p-m of Ho3+ ions are investigated. The maximum emission cross section of the above sample at 2.0 p.m is calculated to be 1.08 × 10-20 cm2 for the LiYF4 single crystal of 1-mol% Ho3+ and 6-mo1% Yb3+ according to the measured absorption spectrum. The high energy transfer efficiency of 88.9% from Yb3+ to Ho3+ ion in the sample co-doped by Ho3+ (1 mol%) and Yb3+ (8 tool%) demonstrates that the Yb3+ ions can efficiently sensitize the Ho3+ ions.
文摘The vacuum ultraviolet (VUV) spectroscopic properties of praseodymium (Pr3+, 1at%) doped LaF3 nanocrystals/glass at room temperature and 20 K are reported. Two types of Pr3+ ions, those in LaF3 nanocrystals and those in the glass host, were excited to 4f 5d band by VUV using synchrotron radiation as an excitation source, and emissions of 1S0 → 1D2 (336 nm), 1S0 → 1I6 (397 nm ) of Pr3+ in the nanocrystals and emissions of 4f 5d → 3HJ, 3FJ of Pr3+ in the glass appeared at the same time. But unlike in the bulk sample crystals, emission of 3P0 → 3HJ, 3FJ as the second step of the quantum splitting (QS) of Pr3+ in the LaF3 nanocrystals was not observed at room temperature, which could be explained that Pr3+ ions in the glass absorbed the energy of 3P0 → 3H4 of Pr3+ in the nanocrystals. Two types of excitation spectra monitoring different emissions were also measured, so it could be observed that the lowest energy of 4f 5d band of Pr3+ in the nanocrystals was about 53 500 cm-1 (186 nm) and in the glass about 33 800 cm-1(295 nm), respectively. These emission and excitation spectra were contrasted to those of bulk sample crystals LaF3∶Pr3+.
基金supported by the National Natural Science Foundation of China (Nos. 51272109 and 50972061)the Natural Science Foundation of Zhejiang Province(Nos. R4100364 and Z4110072)+1 种基金the Natural Science Foundation of Ningbo City (No. 2012A610115)the K. C. Wong Magna Fund in Ningbo University
文摘A Dy3+-doped LiYF4 single crystal capable of generating white light by simultaneous blue and yellow light emission of phosphorescent centers is produced. Chromaticity coordinates and photoluminescence intensity vary with excitation wavelength. Under 350, 365, and 388 nm excitation, the crystal shows excellent white light emission. The most efficient wavelength for white light is 388 nm. The CIE coordina.tes are x=0.316 and y =0.321, and the color temperature (Tc) is 6 368 K. These results indicate that the studied crystal is a potential candidate for ultraviolet light-excited white light-emitting diodes.
基金supported by the National Natural Science Foundation of China(Grant Nos.51272109 and 50972061)the Natural Science Foundation of Zhejiang Province(Grant Nos.R4100364)the Natural Science Foundation of Ningbo City(Grant No.2012A610115)
文摘The LiYF4 single crystals singly doped Ho3+ and co-doped Ho3+, Pr3+ ions were grown by a modified Bridgman method. The Judd-Ofelt strength parameters (Ω2, Ω4, Ω6) of No3+ were calculated according to the absorption spectra and the Judd-Ofelt theory, by which the radiative transition probabilities (A), fluorescence branching ratios (β) and radiative lifetime (τ rad) were obtained. The radiative lifetimes of 5/6 and 5/7 levels in Ho3+ (1 mol%):LiYF4 are 10.89 and 20.19 ms, respectively, while 9.77 and 18.50 ms in Ho3+/pr3+ doped crystals. Hence, the τ rad of 5/7 level decreases significantly by introduction of Pr3+ into Ho3+:LiYF4 crystal which is beneficial to the emission of 2.9 μm. The maximum emission cross section of Ho3+:LiYF4 crystal located at 2.05 μm calculated by McCumber theory is 0.51 ×10-20 cm2 which is compared with other crystals. The maximum emission cross section at 2948 nm in Ho3+/pr3+ co-doped LiYF4 crystal obtained by Fuchtbauer- Ladenburg theory is 0.68 × 10-20 cm2, and is larger than the value of 0.53 × 10-20 cm2 in Ho3+ singly doped LiYF4 crystal. Based on the absorption and emission cross section spectra, the gain cross section spectra were calculated. In the Ho3- ions singly doped LiYF4 crystal, the gain cross sections for 2.05 μm infrared emission becomes positive once the population inversion level reaches 30%. It means that the pump threshold for obtaining 2.05 μm laser is probably lower which is an advantage for Ho3+-doped LiYF4 2.05 μm infrared lasers. The calculated gain cross section for 2.9 μm mid-infrared emission does not become positive until the population inversion level reaches 40% in Ho3+/pr3+:LiYF4 crystal, but 50% in Ho3+ singly doped LiYF4 crystal, indicating that a low pumping threshold is achieved for the H03+:5/6 → 5/7 laser operation with the introduction of Pr3+ ions. It was also demonstrated that Pr3+ ion can deplete rapidly the lower laser Ho3+:5/7 level and has influence on the Ho3+:5/6 level. The Ho3+/pr3+:LiYF4 crystal may be a potential media for 2.9 μm mid-infrared laser.
文摘The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is proposed.
基金Project supported by Changchun Science and Technology Bureau (2009110)Jilin Provincial Education Department (2009JYT15)Jilin Pro-vincial Science and Technology Department (20100556)
文摘The LiYF4 single crystal codoped with thulium and holmium ions was successfully grown by the Cz method. The optimal technical parameters obtained were as follows: the pulling rate was 0.16 mm/h; the rotation speed was 3 rpm; the cooling rate was 15 °C/h. The result of XRD curve showed that as-grown Tm,Ho:LiYF4 laser crystal belonged to the monoclinic system with scheelite-type structure and space group I41/a. The cell parameters calculated were: a=0.52160 nm, c=1.09841 nm and Z=4. Absorption and fluorescence spectra of Tm,Ho:LiYF4 laser crystal at room temperature were measured and analysed. The absorption cross section, FWHM and absorption coefficient at 779.3 nm calculated were 7.44×10–21 cm2, 8.7 nm and 2.23 cm–1, respectively. An intensive fluorescence emission peak appeared near 2045 nm. The emission cross section and fluorescence lifetime were 0.87×10–20 cm2 and 10.8 ms, respectively. The ratio of Tm–Ho transfer to its back-transfer process was 10.6.
基金supported by the National Natural Science Foundation of China(Nos.51272109 and 50972061)the Natural Science Foundation of Zhejiang Province(No.R4100364)+1 种基金the Natural Science Foundation of Ningbo City(No.2012A610115)the K.C.Wong Magna Fund in Ningbo University
文摘Mid-infrared(MIR) emissions of 2.4 and 3.5 μm from Tm3+:LiYF4 single crystals attributed to3H4 →3H5 and3H5 →3F4 transitions as well as MIR emissions of 4.2,4.3,and 4.5 μm from Nd3+:LiYF4 lasers attributed to4I15/2 →4I13/2,4I13/2 →4I11/2,and4I11/2 →4I9/2 transitions,respectively,are observed.LiYF4 single crystals possess high transmittance of over 85% in the 2.5-6 μm range.The large emission crosssections of Tm-doped crystals at 2.4 μm(1.9×10-20cm2) and Nd-doped crystals at 4.2 μm(0.84×10-20 cm2) as well as the high rare-earth doping concentrations,excellent optical transmission,and chemicalphysical properties of the resultant samples indicate that Nd3+and Tm3+singly doped crystals may be promising materials for application in MIR lasers.
基金Project supported by the National Natural Science Foundation of China (10874173,10704090,11074315,11011120083)the Foundation of the Education Committee of Chongqing (KJ090523)the Knowledge Innovation Project of the Chinese Academy of Sciences (KJCX2-YW-M1)
文摘The 4f-5d transitions of Er3+ ions doped in crystals were widely studi ed due to their potential applications in quantum cutting phosphors and VUV lase rs,etc.The theory to do the calculations of 4f-5d transitions and various rela ted aspects,such as the ways to determining various parameters,were summarized .The impacts of various interactions on the spectra were also demonstrated clea rly with Er3+ ions in crystals CaF2 and LiYF4.Predicted results were compared w ith measured spectra.
基金Project supported by the National Key Basic Research Program of China(2013CB921800)the National Natural Science Foundation of China(11274299,11374291,11574298,11204292,11404321)the Anhui Provincial Natural Science Foundation(1308085QE75)
文摘Based on the completely parametric crystal-field model, the energy level parameters, including free-ion parameters and crystal-field parameters, obtained by fitting the experimental energy level data sets of Ln^(3+) in LiYF_4 were systematically analyzed. The results revealed that the regular variation trends of the major parameters at relatively low site symmetry still existed. The g factors of ground states were calculated using the parameters obtained from least-squares fitting. The results for Ce^(3+), Nd^(3+), Sm^(3+), Dy^(3+) and Yb^(3+) were in good agreement with experiment, while those of Er^(3+) deviated from experiment dramatically. Further study showed that the g factors depended strongly on B_4~6, and a slightly different B_4~6 value of -580cm^(-1) led to g factors agreeing well with the experimental values.