Study On Atomic Single And Two-photon Electromagnetically Induced Transparency Spectra

Electromagnetically induced transparency is one of the important phenomena of interaction between light and atomic system. In general, light can be absorbed by the atomic system when the light interacts with medium. This phenomenon is the transparency for a probe field through atomic system which is driven by a strong coupling field. It is due to the quantum interference induced by the coupling field which is applied on the atom. There appear many interesting physical phenomena together with EIT, such as lasing without inversion, large dispersion without absorption, giant optical nonlinearity at low photon level, propagation at slow velocity, and so on. At the same time, the concept of EIT has been generalized by many researchers. The EIT in the three-level (including A,V and Ξ-type) atomic system has been generalized to that in four-level or more level than four-level atomic system. The single EIT (near a frequency) has been generalized to double or multi-ply EIT which simultaneously happens at different frequency. The single-photon EIT (only for a single probe field) has been generalized to multi-photon EIT (for two or more fields). This plays an important role in multi-channel and quantum communication. In the present thesis, we apply coherent fields (microwave fields) to modulate the single or two-photon transparency spectra, which can lead to the transparency with multi-transparency windows. The width of transparency window and the frequency at which the EIT is created can be modulated by adjusting the strength or detuing for the coherent field.· In chapter1, the electromagnetically induced transparency phenomenon and its development are introduced. In chapter2, two and three-level atoms are chosen as examples to describe the interaction between light and medium by using semi-classical theory, and then to introduce the EIT phenomenon, which is physically explained by using interference paths, dressed basis and density matrix.· In chapter3, a five-level atom is proposed. We have found that some absorption peaks are induced by using two coherent fields, which split the EIT window into three parts. The height of the induced absorption peaks is determined by the Rabi frequency of the coherent field, and the location where the peak appears is determined by detuning. This plays an important role in the modulation of the optical information channels.· In chapter6, a six-level atom with more complicated configuration is proposed. A pumping transition is connected to the ground level of the probe transition in the atom used in chapter5. Two-photon EIT has been discussed in this chapter. The modulation of the two-photon EIT spectra can be realized by adjusting the strengths and the detunings of the two coherent fields. The absorption peaks with the same number as the coherent fields, which split the two-photon EIT spectrum with one transparency window into multi-windows. The width and the height of the induced absorption peaks are modulated by adjusting the strength of the coherent fields. Its location at which the induced absorption peak appears is determined by the detuning. In the last chapter, the summary and the prospect are presented.