Experimental And Theoretical Research On Magneto-optical Trap And Optical Dipole Trap Of Cesium Atoms

The interaction between atoms and photons has been investigated comprehensively by Cavity Quantum Electronics-Dynamic (Cavity QED) in the last decades. With the manipulation of atoms developed by laser cooling and trapping and improvement of high finesses cavity with ultra-low losses, the interaction between atoms and photons has reached what is called strong-coupling range in optical domain. In this case, an entangled atom-photon-cavity system is established and this very novel system is widely used for quantum information science, such as quantum measurement, quantum computation, quantum state preparation, quantum communication, etc.But the most difficult and important part of building such entanglement machine is to control definitely the individual atoms. With the progress of laser cooling and trapping, the neutral atoms have been cooled and trapped. Even a single atom now can be controlled by an optical dipole trap and singe atom and single-photon strong interaction and controlling each other have been demonstrated inside an optical cavity, although trapping a single atom for a long time is still a challenge.There are three main parts in this thesis. In the first part, we describe the designing and construction of vapor cell magneto-optical trap (VCMOT) in our lab. Then, show the optical dipole trap of cesium based on the work of VCMOT. In the third part, some preparation works for cavity QED research are presented. The main works and results we have accomplished are as follows:1) Red-detuned locking of cooling/trapping laser to the cycling transition of cesium cooling has been accomplished by means of a double-passed acoustic-optical frequency shifting system and the technique of saturated absorption spectroscopy. The short-term residual frequency jitter is less than 350KHz;2) Automatic controlling system by computer programs has been established for laser cooling and trapping and cavity QED experiment. The laser and magnetic fields can be controlled by the acoustic-optical modulator and the electronic-controlled logic gate respectively.3) An ultrahigh-vacuum chamber and its vacuum pumps system are designed and constructed for cesium VCMOT and cavity QED. Vacuum degree of 2.5 10-6Pa and 8.6 10-7Pa can be maintained for a long period;4) A finely optical system has been designed and constructed for our cesium VCMOT. The system has its own style. The trapping beams can be independently adjustable and three double-passed circularly polarized cooling/trapping beams intersect at the center of MOT. About 1 107 cesium atoms with equivalent temperature of ~270 K are successfully trapped in our VCMOT.5) A single focused transverse red-detuned laser beam is employed to construct the optical dipole trap. The position and waist of laser beam can be adjusted conveniently. The detuning of the trapping laser is 120GHz and laser power near the focus is about 300m W. The dipole trap is characterized via the fluorescence of trapped cesium atoms. The measured light shift is 24MHz.6) The standing-wave optical dipole trap in the ultra-high finesse micro-cavity is discussed. Some factors related to the trap potential and heating rate are considered, such as the laser detuning, the changing of cavity length, laser power of trapping beam, and the linewidth of laser.7) An ultra-high finesse micro-cavity is established in our lab. The cavity length is measured to be about 48 m and the cavity losses are determined by the cavity ring-down(CRD) technique. The finesse of the micro cavity is measured to be 203,000. The corresponding critical photon number mo and critical atom -number no is 0.007and 0.03 respectively. Both of them are much less than 1, which shows the possibility of researching the strong interaction between atoms and photons.8) A balanced optical heterodyne detection system is established. The cw minimum measurable power of 3.5fW is reached, whereas the minimum detectable mean photon number of...