| Quantum optics focus on the interaction of atoms and light, in the domain the light can be used to prepare and control the quantum state of atoms or ions. Based on the atomic coherence, many quantum effects have been found. The information of the coherent process between pump and probe light fields and the atomic medium can be obtained via the probe absorption spectra. The electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) have become tools to prepare the quantum state in atomic vapour cell. In addition, laser cooling and trapping of neutral atoms could distinctly avoid the thermodynamic phenomena and processes and make the quantum effects emerge.The works in this thesis beginning with the basical lab configuration, step by step, we developed several homemade grating-external cavity diode lasers (ECDL) and realized the frequency stabilization. Then, with the homemade ECDLs, EIT and EIA coherent spectra have been experimentally investigated. But precision of these coherence spectra is also limited by the Doppler effect. By virtue of the laser cooling and trapping, we can prepare the atomic sample with a temperature of sub mK, in which the Doppler effect can be greatly inhibited. With the development of technologies of cold atoms, preparing and controlling of atomic quantum state shuld be realized. In this thesis main works are as followings:1) Based on the original ECDL configuration, we improve the design and assemble several ECDL systems. They all can be used to driver the transition of Cesium D2 line, with a frequency tunable range of approxinatly 2GHz.2) With the frequency reference of Cesium saturated absorption spectrum (SAS) or Fabry-Perot cavity and the modulation or modulation-free locking scheme, our homemade ECDL can be stabilized by a feedback loop, the frequency fluctuation is less than 1MHz in 50 seconds.3) Based on the degenerated two-level Cesium system 62S1/2Fg=3→62P3/2Fe=2 or 62S1/2Fg=4→62P3/2Fe=5, the EIT and EIA have been investigated via pump-probe spectra.The effect of the intensity and detuning of different coupling laser on EIT and EIA were also demonstrated in experiments. Within the Doppler background, optical pumping among Zeeman sublevels and the speed selection mechanism dominate the spectra.4) With a detuning-fixed intense coupling laser and a frequency scanning probe beam, three-level laser-driven atomic system can be described with the dressed atom picture. The Autler-Townes doublet is experimentally investigated in the doppler-broaded cesium vapor cell. In a Atype three-level system, sub-Doppler spectra have been observed via the probe absorption. And a novel spectra followed by probe scanning is realized by detecting the transmission of the coupling laser. The effects of coupling laser intensity on the splitting and linewidth of the Autler-Townes doublet are experimentally investigated.5) With red-detuning offset locking of cooling & trapping laser, the detuning of cooling laser can be convientialy controllable. By means of double-passed acoustic-optical-frequency shifting system,three pairs of circularly polarized cooling beams intersect at the center of ultrahigh vacuum chamber, vapor cell magneto-optical trap (VCMOT) is realized. About 107 cesium atoms with temperature of 30-50μK are prepared. With developing and improving the programmable controlling system, some external performance part such as voltage controlled oscillator (VCO), acoustic-optical modulator (AOM), radio frequency switch and Magnetic coil circuit switch can be controlled following a programmed time sequence. So the laser intensity, laser detuning and magnetic fields can be controlled.6) After the MOT is released, the cold atoms drop in gravitational field and expand freely with its initial velocity distribution. With the computer controlling of laser and magnetic fields, we setup the system for the fluorescence or absorption detection. So we can measure the number of cold atoms by probe absorption, and derived the temperature of cold atoms from traditional fluorescence time of flight (TOF) spectra or short distance TOF absorption spectra. By virtue of these results, we optimized the MOT, optical molasses and optical lattices parameters.7) Following the MOT, the further sub-Dopplerσ+-σ- cooling stage are realized, the 3D optical molasses are domonstrated. Employing the short distance TOF spectra as a tools, we investigatd the optical molasses cooling.8) A four beams lin⊥lin 3D near resonace optical lattices (NROL) are constructed in the lab. We also successful transfer the atoms from MOT to optical molasses, at last to optical lattice stage. The intensity and detuning effects of lattice beams have been experimentally investiageted. Finally, atoms trapped in the optical lattice with thetemperature of 10μK have a life time about 70ms.
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