Ultra low cost single chamber BEC apparatus with
Ultra low cost single chamber BEC apparatus with good optical access 王如泉 Laboratory for Solid State Quantum Information Science The Institute of Physics The 4 th Young Researcher Symposium on Cold Atom Physics and Quantum information Dalian, China August 5 th, 2010
Atomic experiments at IOP BEC of 87 Rb Post doc 王晓锐 Graduate students 罗鑫宇 高奎意 Past student 曹强 Ultra sensitive optical pumped atomic magnetometer Graduate students 曹强 Past students 吴莎,伏吉庆,孔嘉 87 Rb-40 K-6 Li Bose-Fermi mixture Post doc 张文卓 Graduate students 张峰 岳振华 刘鹏飞 Technician 赵渤 Quantum memory based on 87 Rb in optical lattice (cooperation with 吴令安) Graduate students 裴莉亚 芦晓刚
BEC of 87 Rb n BEC apparatus technical details q q q n n Single chamber design Home made DFB diode laser with simple frequency lock scheme All injection lock based laser system Second order RF modulation injection lock for repumping light Unique dark MOT scheme Home developed real time timing control system based on C and Labview BEC results Future improvements
Single chamber vs. double MOT BEC Single chamber BEC JILA 103 pure BEC Stanford 104 pure BEC IOP 105 pure BEC Single chamber BEC Double MOT BEC
Single chamber design vs. Double MOT design: advantages and disadvantages Single chamber Double MOT Vacuum 1 chamber 1 pump 2 chambers 2 pumps Laser cooling 6 laser beams 13 laser beams Optical access 4 free directions 2 D optical lattice 3 free directions 1 D optical lattice No. of BEC atoms 1 x 105 (2~ 5)x 105
Vacuum chamber details
DFB diode laser vs. external-cavity laser 1. Great mechanical stability 2. Large mode hopping free tuning range 3. Very repeatable frequency tuning 4. High precision temperature control (1 m. K) 5. Less frequency cover 6. Broader line width
Saturated spectroscopy F=3 F=2 F=1 F=0 780. 2 nm F=2 6834. 7 MHz F=1
Home made master DFB laser Precision temperature controller Magnetic field modulator Master laser To-3 package DFB diode with peltier cooler Precision current controller, Ramp generator and PID
Cooling laser system diagram 200 MHz AOM Saturation spectroscopy Loading laser MOT Loading (frequency lock precision <1 Mhz) Master laser Level 1 slave Detection and optical pumping Cooling laser 200 MHz AOM Repumping laser 80 MHz AOM 3. 4 GHz RF Modulation To other slave lasers For laser pumped atomic magnetometer 100 MHz AOM Double pass Repumping CMOT & PGC
Home made injection lock lasers Injection lock current controller 4 injection lock lasers Injection lock temperature regulator
Injection lock to the 2 nd RF modulated harmonic side band Master laser Free running slave 6. 83 GHz Injected slave 频率
Dark MOT dark mot: cooling -15 MHz, loading -16. 5 normal mot: cooling -15 MHz, loading -15 MHz cooling power 20 m. W, diameter 11. 4 mm, total intensity 19. 6 m. W/cm^2 loading power 80 m. W, diameter 22 mm, total intensity 21 m. W/cm^2
QUIC trap: 3 D magnetic field simulation XY plane equipotential lines Structure of the QUIC trap Finite element thermal simulation Axial magnetic field Home-made QUIC trap coils
Typical QUIC trap performance 研究小组 轴向曲率Gs/cm^2 径向梯度Gs/cm 物理所 317 210 Hansch 260 225 York University 289 ? 北大 260 225 武汉物理所(Ver 1) The University of Texas at Austin 167 189 195 235
Timing control system 31 channel Digital output PC Timing output data with C++ Output data file AO, DO & Trigger System monitor with Labview Powreful control system Bug fee operation …… PCI 6534 RTSI PCI 6713 trigger FPI 3 8 channel Analog …… channel
Imaging system
Experimental results MOT CMOT 10 m s PGC Quadruple trap
Cooling parameters 原子数 /106 温度 /u. K 密度/cm 3 PSD MOT 5*107 80 2*1010 1*10 -7 CMOT 4. 5*107 60 2*1011 0. 5*10 -6 PGC 4*107 27 0. 2*1011 1*10 -6 Quadruple trap 3*107 160 2*1011 5*10 -7 QUIC trap 3*107 130 1*1011 5*10 -7
Vacuum trap life
1070 KHz 1060 KHz Pure BEC has about 1*105 atoms Final evaporation frequency: 1070, 1060, 1045 KHz. Time of flight 20 ms. 1045 KHz
Anisotropic BEC expansion Anisotropic free expansion of BEC time of expansion : 1 ms, 5 ms, 9 ms, 13 ms, 17 ms
Future improvements: LIAD C. Klempt et al. Light induced atom desorption (LIAD) can greatly increase atom number (5× 105 pure BEC expected)
Future improvements: transfer and Feshbach coils, ultra high resolution in situ imaging n n n Additional transfer coils will be added to achieve full 3 D optical access High spatial imaging resolution <2μm Feschbach resonance coils
87 Rb-40 K-6 Li Bose Fermi Mixture Motivation • Extremely large Diopole-dipole interaction with hetero-nucleus molecules • System stability under cold collision
Experimental difficulties Run away condition 87 Rb-40 K-6 Li Ultra low collision cross section 87 Rb-87 Rb |a|=100 a 0 7 Li-7 Li |a|=30 a 0 Successful group #1 Dickerman Evaporation time =60 s, small degenerate atom No Successful group #2 R. Grimm 100 W dipole trap, very small degenerate atom No Complicated laser system for STIRAP two lasers locked to a optical frequency comb mixture
Mini-trap, BEC of 7 Li Power dissipation <10 W at 120 A Radial field gradient 500 G/cm Axial oscillation frequency 60 Hz Trap depth 80 G
Thank you for your attention!
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