In this paper, employing the stochastic differential equations associated with the normal ordering, the quantum properties of a nondegenerate three-level cascade laser with a parametric amplifier and coupled to a two-mode thermal reservoir are thoroughly analyzed. Particularly, the enhancement of squeezing and the amplification of photon entanglement of the two-mode cavity light are investigated. It is found that the two cavity modes are strongly entangled and the degree of entanglement is directly related to the two-mode squeezing. Despite the fact that the entanglement and squeezing decrease with the increment of the mean photon number of the thermal reservoir, strong amount of these nonclassical properties can be generated for a considerable amount of thermal noise with the help of the nonlinear crystal introduced into the laser cavity. Moreover, the squeezing and entanglement of the cavity radiation enhance with the rate of atomic injection.

Thin films of KY3F10 : Ho3+ have been successfully prepared by the pulsed laser deposition with a Nd-YAG laser (266 nm, pulse duration of 10 ns, repetition rate of 2 Hz) on a 1 cm × 1 cm silicon substrate in vacuum and for different target-to-substrate distances. The X-ray diffraction (XRD) results show that the films crystallized in the tetragonal polycrystalline phase of KY3F10 (in agreement with JCPDS card No. 27-0465). Theoretical predictions of the thickness profile have been presented, by using some experimental parameters used in the deposition. Assuming the ellipsoidal expansion of the plasma plume, the thickness profiles of films have been estimated from the solution of the gas dynamical equations for the adiabatic expansion of the plasma plume into vacuum. The results show the strong forward direction of the plume and are in a good agreement with experimental results. Both theoretical and experimental results show a decrease in the film thickness for relatively larger values of the target-to-substrate distance, and this could be attributed to a decrease in the deposition rate at such larger distances. Moreover, for a single film, the thickness also decreases for relatively larger radial angles with respect to the normal to the substrate. K e y w o r d s: thickness profile, gas dynamic equations, plasma plume. IntroductionPulsed laser deposition (PLD) is a thin film deposition technique, which has been a popular, versatile, and highly flexible method for the thin film growth for various materials [1][2][3]. Using this technique, the advantage of controlling a thin film stoichiometry accurately can be achieved by controlling the deposition parameters. The expansion of a laser-induced plasma plume increases on its way from the target to the substrate. This varies the particle flux of the target species over the substrate area, which makes the different parts of the same film to have slightly different thicknesses. It is reported that, near the axis of the plasma plume, the angular distribution of the flux species is proportional to cos , where ≫ 1 and is the radial angle with respect to the normal to the substrate [4]. The cause for this strong forward direction is the strong differences in pressure gradients in axial and radial directions. R.K. Singh and J. Narayan investigated the problem of the angular distribution of the mass flow in the plasma expansion, c ○ N. GEMECHU, T. ABEBE, 2018 by using the isothermal solution of the following gas dynamical equations with Gaussian pressure and density profiles [5]:where , , , and are the density, pressure, velocity, and entropy, respectively. However, since there exists a considerable temperature gradient inside the plasma plume [4,6], the consideration of isothermal solutions is inadequate for the description of PLD. S.I. Anisimov et al. considered the adiabatic expansion of a plume, which is a more realistic situation [4] and described the ellipsoidal expansion of a plasma plume in to vacuum by the above gas dynamic equations as well. By assuming that the...

The dynamics of a coherently driven two-level atom with parametric amplifier and coupled to a vacuum reservoir is analyzed. The combination of the master equation and the quantum Langevin equation is presented to study the quantum properties of light. By using these equations, we have determined the time evolution of the expectation values of the cavity mode and atomic operators. Moreover, with the aid of these results, the correlation properties of noise operators, and the large-time approximation scheme, we calculate the mean photon number, power spectrum, second-order correlation function, and quadrature variances for the cavity-mode light and fluorescence. It is found that the half-width of the power spectrum for the fluorescent light in the presence of a parametric amplifier increases, while it decreases for the cavity-mode light. Moreover, we have found the probability for the atom to be in the upper level in the presence of a parametric amplifier.

We have analyzed the squeezing and statistical properties of the cavity light beam produced by a coherently driven degenerate three-level laser with a degenerate parametric amplifier (DPA) 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. Applying the solutions of the equations of evolution for the expectation values of the atomic operators and the quantum Langevin equation for the cavity mode operator, the mean photon number and the quadrature squeezing of the cavity light are calculated. And a large part of the mean photon number is confined in a relatively small frequency interval. Furthermore, we also obtain the antinormally ordered characteristic function defined in the Heisenberg picture. With the aid of the resulting characteristic function, we determine the Q function which is then used to calculate the photon number distribution.

A model of the first and general order kinetics describing the thermoluminescence (TL) from silicon quantum dots consisting of two active electron trap levels and one recombination center is proposed. The two trap levels are located at different trap depths beneath the edge of the conduction band. The rate equations corresponding to each trap level allow us to numerically simulate the variation of the concentration of electrons in the two traps and the TL intensity as a function of the temperature for quantum dots 2-8 nm in diameter. It is shown that the intensity increases with decreasing in the dot size, indicating that the quantum confinement effect enhances the radiative recombination rate. The two peaks of the intensity correspond to the two different active electron trap levels. With an increase in the dot size, the peaks of the intensity corresponding to the deepest trap shift to the high temperature region. The variation of the concentration of electrons in the traps is given, and this result bridges the experimental gap, where the TL glow curves are generated, and the variation of the concentration of electrons in traps is unknown.