Electromagnetically Induced Transparency In Zeeman-sublevel Atoms And Multiple-transparency Windows In Two Laser-driven Atomic System

This thesis is composed of two parts, one is theoretical and experimental discussion of some details related to Electromagnetically induced transparency in Zeeman-sublevel atoms of Rb vapors, the other is theoretical discussion of. Multiple-transparencies lines in a laser-driven atomic system. I. The theoretical and experimental discussion of some details related to Electromagnetically induced transparency in Zeeman-sublevel atoms of Rb vapors. Firstly, we present a three-level Λsystem, show its theory calculation and discussed the physical explanation to the two topics. A qualitative explanation of the relationship between transparency and laser propagation in Doppler broadened media in EIT was presented. To explain the numerical results that co-propagating of ωc and ωp can reduce the effect of Doppler broadening, we used the relationship between dressed states and the detuning of coupling field. The analysis is shown in Fig 1. And then we know that the dressed-state will move as the detuning of the coupling field moves (see Fig. 2), then we can get rone conclusion: the position of the dressed-state will move in the same diection of the movement of the frequency of the laser. This will ensure that the frequency of the laser met by the atoms is still between the dressed-state, and then ensure the condition of the EIT. Secondly, we discuss the theoretical of Electromagnetically induced transparency in Zeeman-sublevel atoms of Rb vapors. We show a relevant energy configuration in 87 Rb atoms with and without the magnetic, shown in Fig.3.In Fig.4 (a)(the dotted line), there is just one clear EIT window in the absence of the magnetic field. But for the magnetic field being, there could be two cases. When the magnetic field is perpendicular to the direction of the laser beam, four EIT windows emerge inside the absorption curve(shown in the dashed line Fig.4 (b)),. And when themagnetic field is parallel to the laser beam , as shown in the dashed of the Fig.4 (c), three EIT windows emerge inside the absorption curve. In addition, to examine the refractive index at the (a) B=0 (b) B=50.0G (c) B=50.0G Fig.4 The absorption and dispersion spectrum as a function of probe detuning. resonance, we plot the real part of the susceptibility as a function of probe detuning in the dotted lines of the Fig.4. We can see medium has large refractive without absorption(see the dotted line of the Fig.4(a)). For Fig.4(b) and (c), we also find that the medium shows large refractive index for these reasonable small absorption, so that the group velocity of the probe laser can be reduced at every EIT windows. Finally, we see the experiment of Electromagnetically induced transparency in Zeeman-sublevel atoms of Rb vapors.First, we introduce the experiment and results of the EIT. All the information of energy levels and optics and measure results can be found from figure 5, 6 and 7. In Fig.5, we show the energy level of the Rb, and the experiment scheme is depicted in Fig.6. The 87Rb atomic vapor contained in a 3-cm long, 3 cm in diameter cylindrical cell and is heated to the temperature of about 50℃.the cell is palced within Helmlotz coils to control.the strength of the magnetic field at the sample. To get the EIT profile, we did as follows: fixed ωc and recorded ? c using the wavelength-meter, scan theωp to get the EIT in Rb atoms. In Fig.7, we show the absorption spectrum of Rb. And we can watch very good picture about EIT (see Fig8), and the dotted line is theory line. We can see our theoretical simulations and analysis are in good agreement with the experimentally measured results. Considering the degenerate Zeeman-sublevels in 87 Rb atoms with the magnetic field on, we get different lines, Fig . 8 EIT of D1 in 87 Rb as shown in Fig.9 and Fig.10. When the magnetic field is perpendicular(a) B=30.0G(b) B=50.0G (parallel) to the direction of the laser beam, we find that the EIT window could splitinto four (three ) narrow windows depending on the direction of the magnetic field relative with the direction of the coherent and probe beams and the polarizations. Fig.9 the absorption when the magnetic field is Perpendicular to the direction of the laser beam with the magnetic-field strength increases, the separation between adjacent peaks get larger and larger, as shown in Fig.9 and Fig.10. And the doted lines is theory lines, we can see the theoretical and experimental spectrums are in good agreement. Absorption(arb.units)Probe Detuning(MHz)C .Multiple-transparency windows in two laser-driven atomic system A Λ-type four-level system interacting with two coherent fields is considered (as shown in Fig.11). We show that the system can become transparent to the probe laser field at two or three different frequencies (see Fig.12), which depends on the strength of the two coherent field. When ? 1 ≠?2, three EIT windows emerge inside the absorption curve(see the dashed line of the Fig.12(b)). And when ? 1 =?2, the EIT window could split into two narrow windows(see the dashed line of the Fig.12(c)). The positions ,width and height of the transparency windows can be manipulated by adjusting the detuning of the driving field. In addition, the group velocity of the probe laser can be reduced at each transparency window(see the dotted lines of the Fig.12).