Four-level System In Quantum Interference

Quantum interference in multi-level and quantum cryptographyhave been interesting topics in the field of quantum optics for recentyears. Many novel physical phenomena such as coherent populationtrapping,lasing without inversion,electromagnetically inducedtransparency and spontaneous emission cancellation based onquantum interference have been discovered. Besides importantacademic values, the result of quantum interference in multi-levelsystem has also promising applications.In this thesis, we try to theoretically and experimentallyinvestigate quantum interference in hybrid resonant system to findthe suitable atomic energy-level schemes that satisfy theinterference conditions, and to explore the influences of quantuminterference on atomic spectrum.So far, quantum interference was investigated largely in three-level system, Based on scheme of driven field and atomic energy-lever, it was fallen into A,V,E configurations. Theoretically, thecancellation effects of quantum interference have been investigatedsystematically. Experimentally, it had only two repots. All the abovedescribed quantum interference effects fall into the category of theelectromagnetic field-atom and molecular interaction. The quantuminterference effects are alsoobserved in radiationless transition.But the constructive quantuminterference has not been reported.In the thesis, by hybrid resonant excitation of sodium atom andsQdium molecular in laser-field this process were studied. The newresults obtained are as following:For the first time, we observed the constructive effects 'ofquantum interference from 4D--4P state. Through a detail analyzea4d discussion by using full quantum- theory of radiation field,s(mi-classic theory of pumping field, and dressed(state theory.For the first time, we dealt with collision-coupling as dressed-state and found that these dressed-states have a cross.In this thesis, we lucubrated that the effect was also affected byIp4rameter b (or a)...