Evaporative Cooling Of⁸⁷ Rb And⁴⁰K Atoms In To BEC And DFG Mixture In An Optical Dipole Traps

Bose-Einstein condensate (BEC for short) and Degenerate Fermi gas (DFG for short) are the most important materials in the condensate physics and ul-tra-cold physics. We can study many phenomena based on the condensate in-stead of the traditional materials. It will bring us more convenience to simulating traditional materials. So scientists try their best to achieve the ultra-cold range about100nK to get BEC and DFG. Firstly, they use RF (radio frequency) or MW (microwave) evaporative cooling in a magnetic trap whose zero point was removed by an Ioffe coils or a far blue-tuned light. But this magnetic evapora-tive cooling method has many disadvantages, such as noise of the current will cause a great shaking of magnetic trap, the construction of the set-up is so com-plicated to fix, and time controller is also complicated to adapting to the steps for evaporative cooling. So we try to reach the ultra-cold range by evaporative cooling in the optical dipole trap.We have already got BEC and DFG in a QUIC magnetic traps using RF evaporative cooling. In this thesis, we make a new set of our experiment—an1064nm crossed optical dipole trap. We recapture the pre-cooled atoms into the optical dipole trap, after loading atoms into the optical dipole trap, we decrease the power of the crossed-dipole beams, and then the last atoms will collide each other, they will reach a lower temperature until reaching the ultra-cold range. Then we get BEC and DFG in dipole trap again.In this thesis, the theory of the optical dipole trap was discussed in details. Especially, the interaction of D1line and D2line of the alkali with dipole light was demonstrated both theoretical and experimental. The trap frequency of the87Rb atoms and40K atoms were calculated and measured respectively. Besides, the setup of the optical dipole traps was showed using a big block. Avoiding the shaking of the pointing and the feedback circuits were introduced at length. And the transportation of the atoms through a long distance was showed briefly. Based on BEC and DFG in optical traps, we study the Feshbach resonance and gauge potential.