Cui, Wei2016-08-292016-08-292016-08-292016-08-12http://hdl.handle.net/10012/10709This thesis presents a method for calculating the absorption of diode lasers in one-photon, two-photon and (Doppler-free) three-photon excitation configurations. The specific three-photon system studied is atomic Rb, 5s1/2 -5p3/2 - 5d5/2 -np. In principle, three-photon excitation allows for perfect compensation of the Doppler effect. The approach of the method is to construct density matrix equations and solve for the steady state density matrix elements. Solutions are obtained numerically. There is no weak intensity restriction for any laser in the excitation system, and the absorption of all the lasers in the excitation system can be evaluated. The design and testing of a low-noise transimpedance amplifier for measuring absorption is presented.enlaser absorptionRydberg (Rubidium) atomsroom temperature vapor cellmuti-level ladder atomic systemDoppler-free configurationlow-noise transimpedance amplifierMaster Thesis