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Taiwan’s
NO.1 BEC
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What is “BEC”
?
量子力學基本理論中物質波波長 λd = h/p，h為普郎克常數，p 為粒子動量，如果將粒子溫度降低，動量也會降低，物質波便隨之增長，當物質波波長相當於原子之間間距時，所有原子可視為一個整體系統，稱之為玻色-愛因斯坦凝聚。1995年，美國的C. E.
Wieman、E. A. Cornall與其助手，使用雷射冷卻和磁阱中的蒸發冷卻將約2000個稀薄的氣態的銣-87原子的溫度降低到170 nK後，獲得實驗上第一個了玻色-愛因斯坦凝聚態。四個月後，麻省理工學院的W.
Ketterle使用鈉-23也獲得了玻色-愛因斯坦凝態。2001年諾貝爾物理獎頒給此三人。
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2003 in
Taiwan CCU……
2003年9月3日，在韓殿君助理教授指導下，透過雙磁光阱系統 (MOT)與TOP磁阱，結合蒸發冷卻達成玻色-愛因斯坦凝聚態，成功製造出台灣第一個玻色-愛因斯坦凝聚態。
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Magneto-Optical Trap
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What is
“Magneto-Optical Trap” ?
磁光阱的原子團(Magneto-optical trap, MOT)，意謂著使用雷射冷卻和磁光陷阱的技術，使真空腔中的原子受到阻力的作用侷限在一個區域。這是一個適合研究低溫物理的系統，原子團的溫度約幾百μK的範圍，密度約為1010atom/cm3。
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Atomic Vapour Samples
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Cold-atom medium
(e.g. BEC, MOT, optical lattices, atom chip)
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Warm gas medium
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Application:
(a) Z-scan (nonlinear absorption & refraction)
(b) Refractive-index spectrum
(c) Enhancement using the interferometer
(d) EIA samples
(e) Image measurement about the saturation absorption
(f) Bloch oscillation in the low-dimensional warm gas lattice
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Z-scan
• Nonlinear
optical properties, Kerr effect
• Doppler-broadening-reduced
medium (cold atoms, MOT)
• Doppler-broadened
medium (warm varpour of Rb & Cs atoms)
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Bloch Oscillations
• Using the
nonlinear optical properties of atomic vapor medium, the refractive index
is enhanced under the high intensity. The system performs the periodity
of simple lattice. When the external field is put into the system, a
drive force pushes the photons to oscillate along the lattice.
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Electromagentically-Induced
Absorption (EIA)
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Quantum interference
(EIT, Λ-type,
V-type, & cascade-type + coherent population trapping)
(EIA, N-type &
polarization-paralleled type in the closed system + spontaneous coherence
transfer)
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Normal and anomalous EIA
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Studying absorption and refraction: (1) Absorption spectrum
(2) Using the interferometer to get the phase spectrum and
refractive-index spectrum, or 2d-group-index image
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Phase-Shifting Imaging
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Nondestructive imaging
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Mach-Zehnder interferometer
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