Laser Cooling And Trapping And Two Photos Absorption Via Quantum Interference

Laser cooling and trapping is an active field in the last few decades (no years). The theoretical and experimental researches on atomic slowdown have been begun since 1970's. This thesis simply reviews the progress of laser cooling and trapping of neutral atoms, and recounts the progress of building our MOT and trapping Rubidium atoms particularly. It also introduces the basic theory on measuring the temperature of cold atoms with short-distance time-of-flight method, and analyzes the error between theoretical and approximate formula. Using semi-classical theory, we analysed the quantum interference effect on the susceptibility of probe beam in N-type four-level cold atomic system. The study results show that the linear absorption of the probe beam can be eliminated remarkably, while the nonlinear absorption of the probe beam can be enhanced remarkably under the appropriate resonant condition.This thesis is divided into two parts: (1) we achieved a single frequency and narrow linewidth diode laser used in the cooling and trapping of Rb atoms by injection locking method. The power of the cooling beam is 60 mw and the wavelength is 780 nm. We realized the cooling and trapping of Rb atoms in MOT. Based on the basic theory of short-distance time-of-flight method, we compared the error between theoretical expressions and approximate expressions.(2) Using semi-classical theory, we analysed the quantum interference effect on the susceptibility of probe beam in N-type four-level atomic system.