In this paper the temperature-related performances of the Yb^3＋：YAG disc laser has been investigated based on quasi-three level rate equation model. A compact diamond window cooling scheme also has been demonstrated...In this paper the temperature-related performances of the Yb^3＋：YAG disc laser has been investigated based on quasi-three level rate equation model. A compact diamond window cooling scheme also has been demonstrated. In this cooling scheme, laser disc is placed between two thin discs of single crystal synthetic diamond, the heat transfer from Yb^3＋：YAG to the diamond, in the direction of the optical axis, and then rapidly conducted radically outward through the diamond to the cooling water at the circumference of the diamond/Yb^3＋ ：YAG assembly. Simulation results show that increasing the thickness of the diamond and the overlap-length （between diamond and water） decreases the disc temperature. Therefore a 0.3-0.5 mm thick diamond window with the overlap-length of 1.5 2.0 mm will provide acceptable cost effective cooling, e.g., with a pump intensity of 15 kW/cm^2 and repetitive rate of 10 Hz, to keep the maximum temperature of the lasing disc below a reasonable value （310K）, the heat exchange coefficient of water should be about 3000 W/m^2K.展开更多
YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. T...YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.展开更多
Yb^(3+):YAG crystal is one excellent material for developing high-power radiation-balanced lasers(RBLs).An experimental study of the laser cooling performances of YAG crystals with various doping Yb^(3+)concentrations...Yb^(3+):YAG crystal is one excellent material for developing high-power radiation-balanced lasers(RBLs).An experimental study of the laser cooling performances of YAG crystals with various doping Yb^(3+)concentrations,especially for application of RBLs,is reported here.With improved Yb^(3+)doping concentration in YAG crystal,though the resonance absorption coefficient increases,the corresponding external quantum efficiency has been found to decrease with the average fluorescence wavelength being red shifted,which is detrimental to anti-Stokes fluorescence(ASF)cooling.The decrease of the external quantum efficiency can cause the first zero crossing wavelength to red shift,which is not conducive to RBLs.Based on the comprehensive study of the cooling characteristics of the series of Yb^(3+)-doped YAG crystals,the optimal Yb3+doping concentration for ASF cooling has been suggested.展开更多
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 met...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.展开更多
文摘In this paper the temperature-related performances of the Yb^3＋：YAG disc laser has been investigated based on quasi-three level rate equation model. A compact diamond window cooling scheme also has been demonstrated. In this cooling scheme, laser disc is placed between two thin discs of single crystal synthetic diamond, the heat transfer from Yb^3＋：YAG to the diamond, in the direction of the optical axis, and then rapidly conducted radically outward through the diamond to the cooling water at the circumference of the diamond/Yb^3＋ ：YAG assembly. Simulation results show that increasing the thickness of the diamond and the overlap-length （between diamond and water） decreases the disc temperature. Therefore a 0.3-0.5 mm thick diamond window with the overlap-length of 1.5 2.0 mm will provide acceptable cost effective cooling, e.g., with a pump intensity of 15 kW/cm^2 and repetitive rate of 10 Hz, to keep the maximum temperature of the lasing disc below a reasonable value （310K）, the heat exchange coefficient of water should be about 3000 W/m^2K.
基金Project supported bythe National Natural Science Foundation of China (50372075)
文摘YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.11604100,11834003,61574056,91536218,and 11874151)the Special Financial Grant from the China Postdoctoral Science Foundation(Grant No.2016T90346)111 Project(No.B12024).B.Zhong thanks L.Z.Deng for helpful discussions.
文摘Yb^(3+):YAG crystal is one excellent material for developing high-power radiation-balanced lasers(RBLs).An experimental study of the laser cooling performances of YAG crystals with various doping Yb^(3+)concentrations,especially for application of RBLs,is reported here.With improved Yb^(3+)doping concentration in YAG crystal,though the resonance absorption coefficient increases,the corresponding external quantum efficiency has been found to decrease with the average fluorescence wavelength being red shifted,which is detrimental to anti-Stokes fluorescence(ASF)cooling.The decrease of the external quantum efficiency can cause the first zero crossing wavelength to red shift,which is not conducive to RBLs.Based on the comprehensive study of the cooling characteristics of the series of Yb^(3+)-doped YAG crystals,the optimal Yb3+doping concentration for ASF cooling has been suggested.
基金supported by the National Natural Science Foundation of China(Grant Nos.61405206,51502292,and 51702322)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant Nos.CXJJ-16M251 and CXJJ-15M055)the National Key Research and Development Program of China(Grant No.2016YFB0402101)
文摘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.
