Coherent atomic states prepared by laser field can have quantum interference\nbetween the different transition amplitudes. Therefore, the medium susceptibility\nand optical response can be engineered, leading to many interesting phenomena, such\nas coherent population trapping (CPT), electromagnetically induced transparency\n(EIT), and lasing without inversion (LWI).\nWe studied the coherence effects in various prototype atomic systems, and found\nmany interesting applications. We solved the slow light bandwidth problem by decomposing\nthe pulse and matching each frequency to its EIT window using a magnetic\nfield gradient. We also considered the probe field deflection induced by the driving\nfield distribution in EIT, and showed that even a broadband pulse can be deflected\nwithout serious spreading. In the fast light area, we examined the effects of noise and\nparameter deviations in a bichromatic Raman type white light cavity. Taking advantage\nof the adjustable absorption of EIT, we showed that EIT in a laser cavity can\nhave either first-order or second-order phase transitions. Last but not least, we show\nthat the adiabatic population transfer can be used to reverse the weak measurement\nof an arbitrary field with finite photon number.
We present a general formalism for studying the interaction between laser fields and degenerate-Zeeman-sublevel atoms correct up to the first order in the weak probe field. We derive from this theory the equations of motion for a \ensuremath{\Lambda}-type system involving
S1/2, F=2\ensuremath{\leftrightarrows}
P1/2, F\ensuremath{'}=1\ensuremath{\leftrightarrows}
S1/2, F=1 transitions in
87Rb atoms. These equations are used to numerically investigate the coherent population trapping (CPT) schemes in the
S1/2, F=2\ensuremath{\leftrightarrows}
P1/2, F\ensuremath{'}=1 transition induced by a linearly polarized pumping field and the electromagnetically induced transparency exhibited in the weak probe spectrum in the
S1/2, F=1\ensuremath{\leftrightarrows}
P1/2, F\ensuremath{'}=1 transition. We discuss the effects of the CPT on the probe spectrum with and without the Doppler broadenings by comparing the probe spectrum derived from the real system with that derived from an ideal \ensuremath{\Lambda}-type system. We show that the atoms in the CPT states are shielded from interacting with the probe field while those in the absorbent states make contributions to the weak probe by the Raman anti-Stokes process, and the effect of the real system on the probe field becomes equivalent to the ideal \ensuremath{\Lambda} system only in the strong CPT parameter regime. \textcopyright{} 1996 The American Physical Society.
The dependence of the shape of resonances of coherent population trapping (CPT) on magnetic sublevels of thallium atoms, forming a generalized Λ-system with the magnetic sublevels of the fine-structure levels as lower ones, on the polarization of the radiation fields has been numerically studied. The cases of linear, elliptical, and circular polarizations have been considered. The shape and the number of CPT resonances for different polarizations have been compared. It has been concluded that the electromagnetically induced transparency can be changed by changing the polarization properties of the laser radiation. The possibility to decrease the number of observed resonances may be useful in high-resolution spectroscopy.
For a transition ${F}_{e}=0\ensuremath{\leftrightarrow}{F}_{g}=1$ driven by a linearly polarized light and probed by a transverse light, which has two equal circular components and is orthogonal to the linear polarization of the drive field and magnetic field, quantum coherence effects are investigated. Due to the coupling between the drive Rabi frequency and the Zeeman splitting, electromagnetically induced transparency, electromagnetically induced absorption, and the transition from positive to negative dispersion are obtained, as well as the populations coherently oscillating with a pump-probe detuning in the steady state. At the zero pump-probe detuning, the subluminal and superluminal light propagations are predicted. Finally, there exist the large population fluctuations when we vary the pump-probe detuning.
In the Λ three-level system, we will make use of semi-classical density matrix method to analyze cesium (Cs) hyperfine structure of coherent population trapping (CPT) phenomenon. Coherent population trapping has been widely used in electromagnetically induced transparency, non-inversion laser, optical storage and ultra-slow speed of light fields, then strong-coupling light and weak detecting light form coherent laser light to change the hyperfine structure energy levels of particles number distribution, which impacts on laser pumping magnetic resonance. In this paper, we will discuss the theoretical analysis and system design of laser pumping cesium magnetometer, cesium atomic energy level formed hyperfine structure with the I-J coupling, the hyperfine structure has been further split into Zeeman sublevels for the effects of magnetic field. To use laser pump and RF magnetic field make electrons transition in the Zeeman sublevels to produce the results of magneto-optical double resonance and on this basis we analyze the influence of laser pumping magnetic resonance based on coherent population trapping.