Coherent Population Transfer And Study On Nonlinear Frequency Conversion Efficiency

Atoms and molecules prepared in well-defined quantum states are instrumental in modern atomic and molecular physics, not only in coherent control of chemical reactions, but also in various new areas, e.g. quantum information, atom optics, light propagation through matter, lasing without inversion, quantum optics, high harmonic generation, and others. Recently, techniques to prepare the atoms and molecules have attracted much attention.In the paper, the first section analyzes Stark-chirped rapid adiabatic passage (SCRAP), which can give a complete transfer of atomic or molecular population between two bound states, by means of level-crossing technique and dressed states theory. The transfer of populations is controlled by the detuning of the pump laser from the transition frequency and the delay between Stark-shifting pulse and pump pulse.1) When the detuning is the range 0 < â–³₀ < S₀ , and the delay between Stark-shifting pulse and pump pulse is zero, the population transfer efficiency is zero between the ground state and excited state. When the delay of the Stark-shifting pulse with respect to the pulse of the coupling-laser Rabi frequency guarantees strong pump intensity of the two resonances while the weak pump intensity. The SCRAP method can give a population-transfer efficiency approaching unity. The population profile becomes asymmetric as is the result of reference paper [36]2) With the theoretical analysis and numerical calculation, when the detuning of the pump laser is equal to zero, the population of two states is equal; the system remains robust and maximum coherence superposition. Moreover, the robustness of the population is insensitive to variations in the intensities of the pump and Stark laser.The potential of the nonlinear optics with maximum coherence has been demonstrated for the regime of undepleted coherence and hence for an undepleted pump field. The second section analyzes the four-wave mixing conversion efficiency with large atomic coherence, considers a process of difference-frequency mixing in the ^ -type three level system. Because of the process of the difference-frequency mixing.