掺杂稀土材料激光冷却的理论研究
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摘要
近年来,基于反斯托克斯荧光制冷的固体材料激光冷却技术得到了快速发
展。本文首先简单介绍了固体材料激光冷却的基本原理及其技术,随后综述了各
种固体激光冷却的新材料、新方案和新结果及其最新实验进展,并介绍了各种荧
光制冷的温度测量技术。最后,展望了反斯托克斯荧光制冷的应用前景和荧光制
冷器的发展。
本文采用简化的二能级系统分析了荧光制冷中的激光抽运-受激辐射过
程。以Tm3+掺杂离子为例,从理论上分析了最小制冷能级间距与激光抽运速率
的关系,研究了不同抽运速率下制冷功率与能级间距的关系以及热-光转换效率
与能级间距的关系,获得了最佳热-光转换效率与抽运速率的关系,从而探讨了
Tm3+掺杂材料用于激光冷却的可行性,并讨论了制冷基体材料的合理选择问题。
本文采用一个二能级系统模型分析了Yb3+离子2F7/2→2F5/2能级之间的吸收
与受激辐射过程,讨论了影响制冷功率的因素,找到了提高制冷功率的途径,详
细分析了掺杂离子浓度、泵浦功率、有效吸收截面对冷却极限的影响。同时对冷
却的物理过程进行了模拟,从而得到了冷却过程中温度随时间的变化曲线,该结
果与实验曲线基本一致,从而验证了采用二能级模型分析反斯托克斯荧光制冷的
合理性。
In recent years, the laser cooling technique of solid materials based on the anti-Stokes fluorescent scattering has obtained fast progress. In this thesis, the basic principle on laser cooling of solid and its technique are first briefly introduced. Second, all of new codling materials, schemes and results and their recent experimental progresses are reviewed in some detail. Meanwhile, different temperature measurement techniques are summarized. Finally, the applied prospect on laser cooling of solid materials and the development of optical refrigerators are briefly discussed and looked ahead.We propose a simplified two-level system to analyze the pumping and stimulated-emission processes. Using the model of Tm~(3+), a theoretical study of the relationship between the minimum energy gap and the laser pumping rate is performed. Under the different pumping rate, the relationship between the energy gap and cooling power and the relationship between the energy gap and heat-light converting efficiency are analyzed. We find the relationship between the optimal heat-light converting efficiency and the pumping rate, and thus prove the feasibility of laser cooling in Thulium-doped material. Meanwhile, the choice of host material is discussed.We propose a two-level model to analyze the absorption and stimulated-emission processes between the Yb~(3+) ~2F_(7/2) ground-state manifold and the ~2F_(5/2) excited-state manifold, and discuss several parameters that influence the cooling power, and find some ways to improve the cooling power. The influences of the doped concentration, pumping power and the effective pump-spot area on laser cooling efficiency are particularly analyzed. At the same time, we make computer simulation about the cooling process and obtain the temperature as a function of the cooling time, it is similar to the experimental results. So this shows that our model is reasonable.
展。本文首先简单介绍了固体材料激光冷却的基本原理及其技术,随后综述了各
种固体激光冷却的新材料、新方案和新结果及其最新实验进展,并介绍了各种荧
光制冷的温度测量技术。最后,展望了反斯托克斯荧光制冷的应用前景和荧光制
冷器的发展。
本文采用简化的二能级系统分析了荧光制冷中的激光抽运-受激辐射过
程。以Tm3+掺杂离子为例,从理论上分析了最小制冷能级间距与激光抽运速率
的关系,研究了不同抽运速率下制冷功率与能级间距的关系以及热-光转换效率
与能级间距的关系,获得了最佳热-光转换效率与抽运速率的关系,从而探讨了
Tm3+掺杂材料用于激光冷却的可行性,并讨论了制冷基体材料的合理选择问题。
本文采用一个二能级系统模型分析了Yb3+离子2F7/2→2F5/2能级之间的吸收
与受激辐射过程,讨论了影响制冷功率的因素,找到了提高制冷功率的途径,详
细分析了掺杂离子浓度、泵浦功率、有效吸收截面对冷却极限的影响。同时对冷
却的物理过程进行了模拟,从而得到了冷却过程中温度随时间的变化曲线,该结
果与实验曲线基本一致,从而验证了采用二能级模型分析反斯托克斯荧光制冷的
合理性。
In recent years, the laser cooling technique of solid materials based on the anti-Stokes fluorescent scattering has obtained fast progress. In this thesis, the basic principle on laser cooling of solid and its technique are first briefly introduced. Second, all of new codling materials, schemes and results and their recent experimental progresses are reviewed in some detail. Meanwhile, different temperature measurement techniques are summarized. Finally, the applied prospect on laser cooling of solid materials and the development of optical refrigerators are briefly discussed and looked ahead.We propose a simplified two-level system to analyze the pumping and stimulated-emission processes. Using the model of Tm~(3+), a theoretical study of the relationship between the minimum energy gap and the laser pumping rate is performed. Under the different pumping rate, the relationship between the energy gap and cooling power and the relationship between the energy gap and heat-light converting efficiency are analyzed. We find the relationship between the optimal heat-light converting efficiency and the pumping rate, and thus prove the feasibility of laser cooling in Thulium-doped material. Meanwhile, the choice of host material is discussed.We propose a two-level model to analyze the absorption and stimulated-emission processes between the Yb~(3+) ~2F_(7/2) ground-state manifold and the ~2F_(5/2) excited-state manifold, and discuss several parameters that influence the cooling power, and find some ways to improve the cooling power. The influences of the doped concentration, pumping power and the effective pump-spot area on laser cooling efficiency are particularly analyzed. At the same time, we make computer simulation about the cooling process and obtain the temperature as a function of the cooling time, it is similar to the experimental results. So this shows that our model is reasonable.
引文
[1] Pringsheim P. Z , Phys, 1929, 57(8) : 739-747.
[2] Vavilov S , J. Phys. (Moscow), 1945,9(1) : 68-71.
[3] Vavilov S, J. Phys. (Moscow), 1946,10(4) : 499-502.
[4] Landau L, J. Phys. (Moscow), 1946, 10(4) : 503-506.
[5] Epstein I, Buchwald MI, Edwards B C , et al. Nature, 1995, 377(12) : 500-502.
[6] Mungan C E , Buchwald M I, Edwards B C , et al. Phys. Rev. Lett., 1997, 78(6) : 1030-1033.
[7] Gosnell T R, Opt. Lett., 1999, 24(15) : 1041-1043.
[8] FinkeiBen E , Potemski M , Wyder P, et al. Appl. Phys. Lett., 1999, 75(9) : 1258-1260.
[9] Hoyt C W , Sheik-Bahae M , Epstein R I , et al. Phys. Rev. Lett., 2000, 85(17) : 3600-3603.
[10] Hoyt C W , Hasselbeck M P , Sheik-Bahae M , et al. J. Opt. Soc. Am. B, 2003, 20(5) : 1066-1074.
[11] Fernandez J , Mendioroz A, Garcia A J , et al, Phys. Rev. B, 2000 , 62(5) : 3213-3217.
[12] 秦伟平,物理学进展, 2000, 20(2) : 93-167.
[13] Murtagh M T., Sigel Jr G H., Fajardo J C., et al. J. Non-Cryst. Solids, 1999 (253) : 50-57.
[14] 衣永青,宁鼎,荆光明.光纤光缆,2003(2) :36-38.
[15] Mendioroz A, Fernandez J, Voda M ,et al. Opt. Lett, 2002, 27(17) : 1525-1527.
[16] 董俊,邓佩珍,徐军等,人工晶体学报,1999,28(2) :140-144.
[17]黄柏标,刘士文,任红文等。固体电子学研究与进展, 1991,11(3): 230-234.
[18] Lamouche G , Lavallard P, Suris R, et al, J. Appl. Phys, 1998, 84(1): 509-516.
[19] Luo X, Eisaman M D, Gosnell T R, Opt. Lett., 1998, 23(8): 639-641.
[20] Rayner A, Friese M E J , Truscott A G , et al. J. Mod. Opt, 2001, 48(1): 103 — 114.
[21] Bowman S R, Mungan C E , Appl. Phys. B, 2000, 71: 807—811.
[22] Epstein RI, Brown J J , Edwards B C , et al, J. Appl. Phys., 2001, 90(9): 4815 — 4819.
[23] Rivlin LA, Zadernovsky AA, Opt. Comm., 1997 ,139: 219-222.
[24] Gauck H, Gfroerer T H, Renn M J , et al, Appl. Phys. A, 1997,64(2): 143 -147.
[25] Rayner A , "Laser cooling of solid ", Ph. D dissertation , University of Queensland Australia, 2002: 1 — 167.
[26] Edwards B C , Anderson J E , Epstein R I, et al, J. Appl. Phys, 1999, 86(11): 6489-6493.
[27] Mungan C E , J. Opt. Soc. Am. B, 2003, 20 (5): 1075-1082.
[2] Vavilov S , J. Phys. (Moscow), 1945,9(1) : 68-71.
[3] Vavilov S, J. Phys. (Moscow), 1946,10(4) : 499-502.
[4] Landau L, J. Phys. (Moscow), 1946, 10(4) : 503-506.
[5] Epstein I, Buchwald MI, Edwards B C , et al. Nature, 1995, 377(12) : 500-502.
[6] Mungan C E , Buchwald M I, Edwards B C , et al. Phys. Rev. Lett., 1997, 78(6) : 1030-1033.
[7] Gosnell T R, Opt. Lett., 1999, 24(15) : 1041-1043.
[8] FinkeiBen E , Potemski M , Wyder P, et al. Appl. Phys. Lett., 1999, 75(9) : 1258-1260.
[9] Hoyt C W , Sheik-Bahae M , Epstein R I , et al. Phys. Rev. Lett., 2000, 85(17) : 3600-3603.
[10] Hoyt C W , Hasselbeck M P , Sheik-Bahae M , et al. J. Opt. Soc. Am. B, 2003, 20(5) : 1066-1074.
[11] Fernandez J , Mendioroz A, Garcia A J , et al, Phys. Rev. B, 2000 , 62(5) : 3213-3217.
[12] 秦伟平,物理学进展, 2000, 20(2) : 93-167.
[13] Murtagh M T., Sigel Jr G H., Fajardo J C., et al. J. Non-Cryst. Solids, 1999 (253) : 50-57.
[14] 衣永青,宁鼎,荆光明.光纤光缆,2003(2) :36-38.
[15] Mendioroz A, Fernandez J, Voda M ,et al. Opt. Lett, 2002, 27(17) : 1525-1527.
[16] 董俊,邓佩珍,徐军等,人工晶体学报,1999,28(2) :140-144.
[17]黄柏标,刘士文,任红文等。固体电子学研究与进展, 1991,11(3): 230-234.
[18] Lamouche G , Lavallard P, Suris R, et al, J. Appl. Phys, 1998, 84(1): 509-516.
[19] Luo X, Eisaman M D, Gosnell T R, Opt. Lett., 1998, 23(8): 639-641.
[20] Rayner A, Friese M E J , Truscott A G , et al. J. Mod. Opt, 2001, 48(1): 103 — 114.
[21] Bowman S R, Mungan C E , Appl. Phys. B, 2000, 71: 807—811.
[22] Epstein RI, Brown J J , Edwards B C , et al, J. Appl. Phys., 2001, 90(9): 4815 — 4819.
[23] Rivlin LA, Zadernovsky AA, Opt. Comm., 1997 ,139: 219-222.
[24] Gauck H, Gfroerer T H, Renn M J , et al, Appl. Phys. A, 1997,64(2): 143 -147.
[25] Rayner A , "Laser cooling of solid ", Ph. D dissertation , University of Queensland Australia, 2002: 1 — 167.
[26] Edwards B C , Anderson J E , Epstein R I, et al, J. Appl. Phys, 1999, 86(11): 6489-6493.
[27] Mungan C E , J. Opt. Soc. Am. B, 2003, 20 (5): 1075-1082.