本文選題：玻色-愛因斯坦凝聚 + 磁轉(zhuǎn)移　； 參考：《山西大學(xué)》2016年博士論文

【摘要】：本文首先介紹了如何從相對低真空度的真空腔室中俘獲高密度超冷玻色氣體,然后運(yùn)用磁轉(zhuǎn)移的辦法,將原子高效率的裝載到超高真空度的二級磁阱中,然后使用遠(yuǎn)失諧的532nm激光封堵磁場零點(diǎn),之后進(jìn)行蒸發(fā)冷卻,最后將87Rb的超冷原子裝載到遠(yuǎn)失諧的交叉偶極阱中,進(jìn)而實(shí)現(xiàn)玻色-愛因斯坦凝聚。在俘獲原子、磁轉(zhuǎn)移冷原子的實(shí)驗(yàn)部分,首先回顧了一些常用的冷卻技術(shù)和概念,其中包括激光冷卻、磁光阱等。然后描述了超冷原子的超高真空腔室系統(tǒng)、實(shí)現(xiàn)超高真空度的方法、搭建簡單可靠穩(wěn)定的激光光路、設(shè)計(jì)四級阱線圈和磁轉(zhuǎn)移線圈、編寫磁轉(zhuǎn)移程序和設(shè)計(jì)控制電路從而使得四級阱和磁轉(zhuǎn)移線圈有序的相互配合、編寫CCD程序從而配合飛行展開吸收成像。在實(shí)驗(yàn)的關(guān)鍵部分,做了詳細(xì)的介紹,例如磁轉(zhuǎn)移線圈的配合部分。其次本文還介紹了鎖相環(huán)的基本原理,分析了不同種類的鑒相器的優(yōu)缺點(diǎn)和實(shí)用性。為了獲得低噪聲、相位相干、差頻大的兩束拉曼激光,介紹了如何將電子鎖相環(huán)推廣到光學(xué)鎖相環(huán),并且設(shè)計(jì)了光學(xué)鎖相環(huán),分析了在調(diào)節(jié)電路過程中的一些關(guān)鍵部件。使用光學(xué)鎖相環(huán)調(diào)制外腔反饋式半導(dǎo)體激光器的壓電陶瓷和電流,進(jìn)而使得非相關(guān)聯(lián)的兩束激光線寬從MHz降低到Hz量級,它們的相噪大幅度降低,將鎖定的兩束拉曼激光照射到超冷原子上,測量了原子態(tài)的拉比振蕩。本文最后介紹了使用兩束拉曼激光作用在超冷原子中模擬電子自旋軌道耦合的模型,并且成功模擬了自旋軌道耦合,然后將一維的自旋軌道耦合推廣到二維空間,使用三束線偏振拉曼光實(shí)現(xiàn)了二維自旋軌道耦合,通過調(diào)節(jié)拉曼光的失諧大小,實(shí)現(xiàn)了狄拉克在動量空間的位置變化。為了拓展二維自旋軌道耦合的應(yīng)用(模擬拓?fù)浠魻栃?yīng)等),在其中一束拉曼光的光路中加入/4波片,由此使得線偏光橢圓極化,由此在二維自旋軌道耦合的哈密頓量中構(gòu)建了垂直于拉曼激光平面的塞曼磁場哈密頓量,通過調(diào)節(jié)入/4波片的角度(調(diào)節(jié)橢圓極化率),就可以調(diào)節(jié)塞曼磁場的大小,由此就將狄拉克點(diǎn)處的帶隙打開,并且通過改變波片的角度可以精確調(diào)節(jié)帶隙的大小。自旋軌道耦合的原子態(tài)之間存在相互作用力,我們通過自旋射頻光譜的技術(shù),使用射頻將原子泵浦到無相互作用的量子態(tài)上,通過能量守恒倒推出相互作用的量子態(tài)的能量色散關(guān)系圖。
[Abstract]:In this paper, we first introduce how to capture the high-density ultra-cold Bose gas from the vacuum chamber with relatively low vacuum, and then use the method of magnetic transfer to load the atom efficiently into the second-order magnetic trap with ultra-high vacuum. Then a remote detuned 532nm laser is used to block the magnetic field zeros, and then evaporative cooling is performed. Finally, the supercooled atoms of 87Rb are loaded into the far detuned cross dipole trap, and the Bose-Einstein condensation is realized. In the experimental part of capture atoms and magnetically transferred cold atoms, some commonly used cooling techniques and concepts are reviewed, including laser cooling, magneto-optic trap and so on. Then, the ultra-high vacuum chamber system of ultra-cold atoms is described, the method of realizing ultra-high vacuum degree, the simple and reliable laser light path, the design of four-well coil and magnetic transfer coil are designed. The magnetic transfer program and control circuit are designed to make the four-well and magnetic transfer coil cooperate in an orderly way, and the CCD program is written to develop absorption imaging with flight. The key parts of the experiment are introduced in detail, such as the matching part of the magnetic transfer coil. Secondly, the basic principle of PLL is introduced, and the advantages and disadvantages and practicability of different kinds of PLL are analyzed. In order to obtain two Raman lasers with low noise, coherent phase and large frequency difference, this paper introduces how to extend electronic phase-locked loop to optical phase-locked loop, designs optical phase-locked loop, and analyzes some key components in the process of adjusting circuit. Using optical phase-locked loop (OPLL) to modulate the piezoelectric ceramics and current of the external cavity feedback semiconductor laser, the linewidth of the non-correlated two beams is reduced from MHz to Hz, and their phase noise is greatly reduced. Two locked Raman lasers were irradiated onto the supercooled atoms, and the rabbi oscillations of the atomic states were measured. In the end, the model of electron spin orbit coupling in ultracold atoms using two Raman laser beams is introduced. The spin orbit coupling is successfully simulated, and then the one-dimensional spin orbit coupling is extended to two dimensional space. Two-dimensional spin orbit coupling is realized by using three-beam linearly polarized Raman light and Dirac's position in momentum space is realized by adjusting the detuning size of Raman light. In order to extend the application of 2-D spin orbit coupling (simulating topological Hall effect etc.), we add 4 wave plates to one of the Raman beams, which leads to the elliptical polarization of linear polarized light. Thus, a Zeeman magnetic field Hamiltonian perpendicular to the Raman laser plane is constructed in the 2-D spin orbit coupling Hamiltonian. By adjusting the angle of the four-wave plate (adjusting the elliptical polarizability), the size of the Zeeman magnetic field can be adjusted. Thus the band gap at the Dirac point is opened and the size of the band gap can be accurately adjusted by changing the angle of the wave plate. There is an interaction between the spin orbit coupled atomic states, and we pump the atoms to quantum states without interaction by using the technique of spin radio frequency spectroscopy. The energy dispersion diagram of the interacting quantum states is derived from the conservation of energy.
【學(xué)位授予單位】：山西大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O469

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