Browsing by Author "Asmelash, Getachew"

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    Dynamics of Degenerate Three-Level Laser With Spontaneous Emission and Noiseless Vacuum Reservoir
    (Addis Ababa University, 2018-02-02) Asmelash, Getachew; Kassahun, Fesseha (PhD)
    In this dissertation we have studied the quantum properties of the cavity light produced by a coherently pumped three-level laser in an open cavity and coupled to a vacuum reservoir via a single-port mirror. We have carried out our analysis by putting the noise operators associated with the vacuum reservoir in normal order and by taking into consideration the interaction of the three-level atoms with the vacuum reservoir outside the cavity. Employing the pertinent master equation for a coherently pumped degenerate three-level atom, we have obtained coupled equations of evolution for the expectation values of the atomic operators. Then applying the large-time approximation scheme to the quantum Langevin equations for the cavity mode operators, we have managed to decouple the equations of evolution for the expectation values of the atomic operators. Applying the solutions of the pertinent equations of evolution, we have calculated the local and global mean photon number, the local and global variance of the photon number, and the local and global quadrature squeezing of the degenerate three-level laser. We have established that a large part of the total mean photon number and the total variance of the photon number are confined in relatively small frequency intervals. Moreover, we have observed that the cavity light is in a squeezed state and the squeezing occurs in the minus qudrature. In addition, we have found that the maximum global quadrature squeezing of the cavity light is 43:42% ( and occurs at = 0:1717 for = 0 ). We have also seen that the cavity light produced by the laser operating under the conditions _ c and _ is in a chaotic state. In addition, we have shown that the presence of the spontaneous emission process leads to a decrease in the mean photon number, the variance of the photon number, and the maximum quadrature squeezing. Furthermore, we have established that the iii maximum local quadrature squeezing of the cavity light is 78:48% ( and occurs at _ = 0:0606 for = 0 ). We have also analyzed the squeezing and statistical properties of a pair of superposed degenerate three-level laser light beams. We have found that the global mean photon number of the superposed two-mode laser light beams is the sum of the global mean photon numbers of the constituent two-mode laser light beams. Furthermore, we have noted that unlike the mean photon number, the variance of the photon number for the superposed two-mode laser light beams is not the sum of the photon-number variances of the constituent two-mode laser light beams. However, it turns out to be four times that of a two-mode laser light beam, for the case in which the separate two-mode laser light beams are identical. Finally, we have found that the superposition of the two-mode laser light beams does not affect the local and global quadrature squeezing, but it increases the global (local) mean photon number and the global (local) variance of the photon number. Thus, we note that the superposition of the two-mode laser light beams leads to a more bright squeezed light.