摘要
在實驗上我們研究了在光偶極阱中銫原子的電磁誘發透明。
光偶極阱是利用高功率雷射(Nd: YAG laser, 波長1064 nm)操作在功率3.4W, 聚焦到寬度150μm, 所以侷限深度是-70 μK, 可以捕抓到原子數量是2.6*〖10〗^5, 得到原子密度是5.5*〖10〗^9 N/cm^3. 在光偶極阱中階梯型電磁誘發透明是被操作在|6S_(1⁄2) F=4┤〉 到 |6^2 P_(3⁄2) F=5┤〉躍遷能階和|6^2 P_(3⁄2) F=5┤〉到 |8^2 S_(1⁄2) F=4┤〉躍遷能階。
探測光束的頻率藉由飽和吸收光譜鎖頻在|6S_(1⁄2) F=4┤〉 到 |6^2 P_(3⁄2) F=5┤〉的躍遷頻率上，此外，耦合光束頻率是藉由室溫EIT完成鎖頻，在耦合光束照射光偶極阱之前，利用聲光調變器調變耦合光束的頻率到|6^2 P_(3⁄2) F=5┤〉to |8^2 S_(1⁄2) F=4┤〉躍遷能階附近，當電磁誘發透明中的耦合光束和探測光束存在光偶極阱中，此時藉由觀測光偶極阱中原子數量的變化，我們可以得到探測光束的透明程度，光偶極阱的每一張影像對應到聲光調變器的不同頻率，因此，我們可以得到電磁誘發透明的曲線，且利用了密度矩陣方法可以模擬到實驗數據。

In this experiment, eletromagnetically induced transparency (EIT) of Cs atoms in far-off-resonance optical trap (FORT) is investigated.
The FORT is consisted by a Nd:YAG laser (1064 nm) of laser power 3.4 W, and focus to 150 μm of beamwaist. The trap depth of FORT is established to be -70 μK and can trap 2.6*〖10〗^5 atoms at FORT with atoms’ density of 5.5*〖10〗^9 1/cm^3.
The cascade EIT in FORT is operated at transitions from |6S_(1⁄2) F=4┤〉 to |6^2 P_(3⁄2) F=5┤〉 and from |6^2 P_(3⁄2) F=5┤〉to |8^2 S_(1⁄2) F=4┤〉. The frequency of a probing beam is locked at transition from |6S_(1⁄2) F=4┤〉 to |6^2 P_(3⁄2) F=5┤〉 by saturation absorption spectrum technology. The frequency of a coupling beam is locked at transition from |6^2 P_(3⁄2) F=5┤〉to |8^2 S_(1⁄2) F=4┤〉 by EIT at room temperature, which is as served in the FORT. By shifting radio frequency of AOM frequency of a coupling beam varies nearby transition from |6^2 P_(3⁄2) F=5┤〉 to |8^2 S_(1⁄2) F=4┤〉. The frequency of a couple beam corresponds to each pictures of FORT. When a coupling and a probing beam act on the FORT, the transparency of a probing beam can be got by observing atom numbers in FORT. Estimating atom numbers in each pictures the EIT curve can be got. The simulation of EIT is done and fits experiment data.

[1] Carl Wieman, Gwenn Flowers, and Sarah Gilbert, “Inexpensive laser cooling and trapping experiment for undergraduate laboratories”, Am. J. Phys. 63, 317 (1995).
[2] D.lucas, P.Horak, and G.Grynberg, ” Sisyphus cooling of rubidium atoms on the D2 line: The role of the neighbouring transitions”,Eur, Phys. J. D, 7, 261 (1999).
[3] Mark Kasevich and Steven Chu, ”Laser Cooling below a Photon Recoil with Three-Level Atoms” Phys. Rev. Lett. 69, 1741 (1992).
[4] D. Boiron, A. Michaud, J. M. Fournier, L. Simard, M. Sprenger, G. Grynberg, and C. Salomon, “Cold and dense cesium clouds in far-detuned dipole traps”,Phys. Rev. A 57, R4106 (1998).
[5] C. J. Foot, Atomic Physics (Oxford University Press,2005).
[6] K.-J. Boller, A. Imamolu, and S. E. Harris, “Observation of electromagnetically induced transparency“, Phys. Rev. Lett. 66, 2593 (1991).
[7] T. Hong, J. M. Doyle, M. Lukin, D. Patterson, A. Zibrov, and M. Prentiss, “Electromagnetically Induced Transparency in Buffer-gas-cooled Rb Vapor”, Phys. Rev. A, 79, 013806 (2009).
[8] B. K. Teo, D. Feldbaum, T. Cubel, J. R. Guest, P. R. Berman, and G. Raithel, ”Autler-Townes spectroscopy of the 5S1/2-5P3/2-44D cascade of cold 85Rb atoms”, Phys. Rev. A 68, 053407 (2003).
[9] Y. Alhassid, Yan V. Fyodorov, T. Gorin, W. Ihra, and B. Mehlig, “Fano Interference and cross-section fluctuations in molecular photodissiociation”, Phys. Rev. A 73, 042711 (2006)
[10] M Stähler, R. Wynands, S. Knappe, J. Kitching, L. Hollberg, A. Taichenachev, and V. Yudin, “Coherent population trapping resonances in thermal 85Rb vapor: D1 versus D2 line excitation”, Opt. Lett. 27, 1472 (2002).
[11] D. A. Steck, Cesium D Line Data, http://steck.us/alkalidata/ (1998).
[12] R. Grimm, M. Weidemüller, Y. B. Ovchinnikov, ” Optical dipole traps for neutral atoms”, Adv. At. Mol. Opt. Phys. 42, 95 (2000).