采用HE_（11）模输出空心光束的原子漏斗与单模光纤束中的原子导引
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摘要
本文简单介绍了中空光束的定义及其产生方法，同时综述了采用中空光纤中红失谐高斯模式、中空光纤中蓝失谐消逝波和蓝失谐暗中空光束实现原子导引的原理、方法和实验及其最新进展，并对各类中空光束的角动量及其转换和应用进行了详细的介绍和讨论。
本文就利用中空光纤中LP_(01)模(标量模型)和HE_(11)模(矢量模型)衍射输出产生中空光束的物理机制进行了详细的理论研究。在弱波导近似下导出了中空光纤中LP_(01)模的电场分布，数值推算了LP_(01)模输出光束的远场和近场分布。从正确的麦克斯韦方程组出发，详细推导了矢量模型下HE_(11)模的场分布，数值计算了HE_(11)模输出中空光束的远场和近场分布，分析了它们的传播特性。研究了各种光纤参数对中空光束输出特性的影响，同时计算了利用HE_(11)模输出中空光束进行原子导引的光学势。此外，我们把中空光纤中LP_(01)模(标量模型)和HE_(11)模(矢量模型)的场分布以及它们各自的输出光束的近场与远场分布进行了比较，发现两种模式的输出光束在近场分布有很大的区别，LP_(01)模输出光束在近场是一个高斯分布，而HE_(11)模输出光束在近场是一个中空光束，在远场两种模式的输出光束分布是基本一致的，这正是由于在中空光纤中采用了弱波导近似以后所引起的误差。此外，我们讨论了HE_(11)模输出中空光束在原子光学中的潜在应用，比如原子导引与原子漏斗等。
最后，提出了采用单模光纤束中间形成的消逝波来实现原子导引的新方案，并进行了相应的理论分析与研究。在本文中，我们采用了二种单模光纤束的方案：其一是利用四根单模光纤来实现原子波导的方案，我们导出了四根单模光纤束组成的类四边形对称中空区域中产生的消逝波光强分布，计算了该中空区域的冷原子光学囚禁势；其二是利用三根单模光纤来实现原子波导的方案，计算了三根单模光纤束组成的类正三角形中空区域中的消逝波光强分布以及该中空区域的冷原子光学囚禁势。研究表明当入射功率仅为mW量级时，该方案即可用于超冷原子的单模波导。
The definition of dark hollow beam (DHB) and its generation are introduced in this thesis. At the same time, the principle, methods and experimental progress of atomic guiding in hollow optical fibers, blue-detuned evanescent wave and dark hollow beams are reviewed in some detail. Finally, the basic definition of the angular momentums of all kinds of the hollow beams and their application are discussed.
The physical mechanism to generate a dark hollow beam from the output beams of a LP01 mode (scalar model) and a HE11 mode (vector model) in a micro-sized hollow optical is analyzed. Under the weakly guiding approximation, we derive the electric-field distribution of the LP01 mode in the hollow fiber. The far- and near-field distribution of the LP01-mode output beam in free space is calculated numerically from Fraunhofer and Fressnel diffraction theory. On the other hand, the electric field and intensity distributions of the HE11 mode in the hollow fiber are calculated by using the exact solutions of Maxwell Equations based on the vector model, and the diffracted near- and far-field distributions of the HE11 -mode output beam under the Fresnel approximation are studies. We derive an analytical expression on the far- field distribution of the HE n -mode output beam in free space and discuss its applicable condition. We also analyze and compare the differences between the HE11- and LP01 -mode output beams, and
find that the near-field distribution of the LPoi-mode output beam is a Gaussian-like one, but the near-field distribution of the HE11 -mode output beam is a doughnut-like one, whereas the far-field distribution of both the LP01- and HE11 -mode output beams are a doughnut one. We also discuss some potential applications of the HE11-mode output beam in atom optics, such as atomic funnel and guiding, and so on.
Finally, we propose two schemes to guide cold atoms in the beam of single-mode fibers. One is evanescent-wave atomic guiding by using four single-mode fibers. We derive the intensity distribution of the evanescent light-wave in the rectangular hollow space of the four single-mode fibers, and calculate the optical potential for guided cold
atoms. The other scheme is evanescent-wave atomic guiding by using three single-mode fibers, and calculate the intensity distribution of the evanescent light-wave in the triangular hollow space and the optical potential for guided cold atoms. Our study shows that these schemes can be used to realize single-mode atomic wavdguide only when the input laser power is equal to a few mW.
本文就利用中空光纤中LP_(01)模(标量模型)和HE_(11)模(矢量模型)衍射输出产生中空光束的物理机制进行了详细的理论研究。在弱波导近似下导出了中空光纤中LP_(01)模的电场分布，数值推算了LP_(01)模输出光束的远场和近场分布。从正确的麦克斯韦方程组出发，详细推导了矢量模型下HE_(11)模的场分布，数值计算了HE_(11)模输出中空光束的远场和近场分布，分析了它们的传播特性。研究了各种光纤参数对中空光束输出特性的影响，同时计算了利用HE_(11)模输出中空光束进行原子导引的光学势。此外，我们把中空光纤中LP_(01)模(标量模型)和HE_(11)模(矢量模型)的场分布以及它们各自的输出光束的近场与远场分布进行了比较，发现两种模式的输出光束在近场分布有很大的区别，LP_(01)模输出光束在近场是一个高斯分布，而HE_(11)模输出光束在近场是一个中空光束，在远场两种模式的输出光束分布是基本一致的，这正是由于在中空光纤中采用了弱波导近似以后所引起的误差。此外，我们讨论了HE_(11)模输出中空光束在原子光学中的潜在应用，比如原子导引与原子漏斗等。
最后，提出了采用单模光纤束中间形成的消逝波来实现原子导引的新方案，并进行了相应的理论分析与研究。在本文中，我们采用了二种单模光纤束的方案：其一是利用四根单模光纤来实现原子波导的方案，我们导出了四根单模光纤束组成的类四边形对称中空区域中产生的消逝波光强分布，计算了该中空区域的冷原子光学囚禁势；其二是利用三根单模光纤来实现原子波导的方案，计算了三根单模光纤束组成的类正三角形中空区域中的消逝波光强分布以及该中空区域的冷原子光学囚禁势。研究表明当入射功率仅为mW量级时，该方案即可用于超冷原子的单模波导。
The definition of dark hollow beam (DHB) and its generation are introduced in this thesis. At the same time, the principle, methods and experimental progress of atomic guiding in hollow optical fibers, blue-detuned evanescent wave and dark hollow beams are reviewed in some detail. Finally, the basic definition of the angular momentums of all kinds of the hollow beams and their application are discussed.
The physical mechanism to generate a dark hollow beam from the output beams of a LP01 mode (scalar model) and a HE11 mode (vector model) in a micro-sized hollow optical is analyzed. Under the weakly guiding approximation, we derive the electric-field distribution of the LP01 mode in the hollow fiber. The far- and near-field distribution of the LP01-mode output beam in free space is calculated numerically from Fraunhofer and Fressnel diffraction theory. On the other hand, the electric field and intensity distributions of the HE11 mode in the hollow fiber are calculated by using the exact solutions of Maxwell Equations based on the vector model, and the diffracted near- and far-field distributions of the HE11 -mode output beam under the Fresnel approximation are studies. We derive an analytical expression on the far- field distribution of the HE n -mode output beam in free space and discuss its applicable condition. We also analyze and compare the differences between the HE11- and LP01 -mode output beams, and
find that the near-field distribution of the LPoi-mode output beam is a Gaussian-like one, but the near-field distribution of the HE11 -mode output beam is a doughnut-like one, whereas the far-field distribution of both the LP01- and HE11 -mode output beams are a doughnut one. We also discuss some potential applications of the HE11-mode output beam in atom optics, such as atomic funnel and guiding, and so on.
Finally, we propose two schemes to guide cold atoms in the beam of single-mode fibers. One is evanescent-wave atomic guiding by using four single-mode fibers. We derive the intensity distribution of the evanescent light-wave in the rectangular hollow space of the four single-mode fibers, and calculate the optical potential for guided cold
atoms. The other scheme is evanescent-wave atomic guiding by using three single-mode fibers, and calculate the intensity distribution of the evanescent light-wave in the triangular hollow space and the optical potential for guided cold atoms. Our study shows that these schemes can be used to realize single-mode atomic wavdguide only when the input laser power is equal to a few mW.
引文
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[42] Courtial. J., et al, Phys. Rev. Lett., 80(15), 3217(1998)
[43] Ashkin. A., et al, Opt. Lett., 11,288(1986)
[44] Simpson. N. B. et al, J. Mod Opt., 43(12), 2485(1996)
[45] Tabosa. J. W. R., et al, Phys. Rev. Lett., 83, 4967(1999)
[46] Allen L., et al, J Opt. B: Quan. Semiclass. Opt., 4, S1 (2002)
[2] J. Durnin, et al,J. Opt. Soc. Am. B, 4(4), 651 (1987).
[3] G. Indebetouw, et al, J. Opt. Soc. Am. B, 6(1), 150 (1989).
[4] X. Wang, et al, Opt. Lett., 18, 767 (1993).
[5] C. Paterson, et al, Opt. Commun., 124, 121 (1996).
[6] A. Vasara, et al, J. Opt. Soc. Am. B, 6(11), 1748 (1989).
[7] H. S. Lee, et al, Phys. Rev. A, 49(6), 4922 (1994).
[8] J. Arlt., et al, Appl. Phys. B, 71,549(2000).
[9] D. McGloin., et al, Appl. Opt., 37(3), 469(1998).
[10] M. W. Beijersbergen, et al, Opt. Commun., 96, 123(1993).
[11] L. Allen, et al, Phys. Rev., A45 (11), 8185(1992).
[12] Jianping Yin, et al, Opt. Commun., 138, 287 (1997).
[13] M. A. Ol'shanii, et al, Opt. Commun., 98, 77 (1993).
[14] S. Marksteiner, et al, Phys. Rev., A50(3), 2680 (1994).
[15] M. J. Renn, et al, Phys. Rev. Lett., 75(18), 3253 (1995).
[16] M. J. Renn, et al, Phys. Rev., A53(2), R648 (1996).
[17] Jianping Yin, et al, Phys. Rev., A58(1), 509 (1998).
[18] Ito H, et al, Phys. Rev. Lett., 76(24), 4500(1996).
[19] Dall R G, et al,J. Opt. B1(1), 396(1999).
[20] Yin Jianping, et al., Opt. Commun., 138, 287(1997).
[21] Yin Jianping, et al., J. Kore. Phys. Soc., 33(3), 362(1998).
[22] Xu Xinye, et al., Phys. Rev., A60(6), 4796(1999).
[23] Ito H, et al, Appl. Phys, Lett., 70(19), 2496(1997).
[24] Yin Jianping, et al., Phys. Rev., A57(3), 1957(1998).
[25] Padgett M. J., et al, Opt. and Quan. Elec., 31,1(1999)
[26] Allen L., et al, Prog. In Optics., 39, 291(1999)
[27] Van Enk., et al, J. Mod Opt., 41(5), 963(1994)
[28] Van Enk., et al, Opt. Commun., 94, 147(1992)
[29] Barnett. Stephen M., et al, Opt. Commun., 110, 670(1994)
[30] J. Arlt., et al, Appl. Phys., B71,549(2000)
[31] Courtial. J., et al, Opt. Commun., 144, 210(1997)
[32] Van Enk. S. J., et al, Opt. Commun., 112, 225(1994)
[33] Nienhuis. Gerard., et al, Opt. Commun., 132, 8(1996)
[34] Courtial. J., et al, Phys. Rev., A56(5),4193(1997)
[35] Dholakia. K., et al, Phys. Rev., 54(5), R3742(1996)
[36] Padgett. M., et al, Am. J. Phys., 64(1), 77(1996)
[37] Courtial. J., et al, Opt. Commun., 173, 269(2000)
[38] He.H, et al, Phys. Rev. Lett., 75(5), 826(1995)
[39] Simpson. N. B., et al, Opt. Lett., 22(1), 52(1997)
[40] Friese. M.E.J., et al, Phys. Rev., A54(2),1593(1996)
[41] Bialynick-Birula. I., et al, Phys. Rev. Lett., 78(13),2539(1997)
[42] Courtial. J., et al, Phys. Rev. Lett., 80(15), 3217(1998)
[43] Ashkin. A., et al, Opt. Lett., 11,288(1986)
[44] Simpson. N. B. et al, J. Mod Opt., 43(12), 2485(1996)
[45] Tabosa. J. W. R., et al, Phys. Rev. Lett., 83, 4967(1999)
[46] Allen L., et al, J Opt. B: Quan. Semiclass. Opt., 4, S1 (2002)