Browsing by Author "Nayfeh, Munir H."
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- Adiabatic Following in Two-Photon TransitionNayfeh, Munir H.; Nayfeh, Ali H. (American Physical Society, 1977-03-01)The coherent interaction of two smoothly varying, near-resonant, two-photon pulses with a three-level system can be described by "two-photon damped Bloch equations" which are analogous to those for a one-photon transition in a two-level system except for the presence of a two-photon coupling and a frequency shift. These equations are solved for the cases γ1, γ2≪Ω, γ1=γ2, and γ2k2ε4Ω2, γ1≪Ω, where γ1 and γ2 are the atomic energy and phase relaxation widths, respectively, and Ω is the Rabi frequency. The leading contribution to the refractive index is intensity dependent, caused by the level shifts inherent in multiphoton processes; it includes a relaxation dependent part which is important at times shorter than γ−11. The second-order contributions depend on the square of the intensity and the time-integrated square of the intensity. The latter contribution, which is relaxation dependent, causes line asymmetry at the long-wavelength wing; it consists of a term proportional to γ2−γ1 and only important at early times and a term proportional to 2γ2−γ1.
- Double Resonance with Pulsed FieldsNayfeh, Munir H.; Nayfeh, Ali H. (American Physical Society, 1979-04-01)An analytical semiclassical expression is derived for the two-photon transition in a three-level system under the influence of two pulsed fields. We study the Autler-Townes doublet as a function of the time dependence of the field amplitudes and the relaxation widths of the levels. The time variations of the field amplitudes cause shifts in the doublet and modify the radiative decay widths of the levels. The validity of the treatment extends into the intermediate-intensity regime.
- Effect of Relaxation on Self-Induced TransparencyNayfeh, Munir H.; Nayfeh, Ali H. (American Physical Society, 1978-09-01)We derive an equation of motion of the Bloch-vector tipping angle and the area theorem in the presence of relaxation. We derive relaxation-dependent shifts in the equilibrium nπ areas. Part of these shifts depends on a weighted time integral of the sine of the area, and hence these shifts remove the propagation degeneracy of pulses having equal areas but different shapes.
- Intensity-Induced Quenching of Absorption of Diatomic Molecules in Two Near-Resonance Laser FieldsNayfeh, Munir H.; King, K.; Hillard, G. B.; Shahin, I. S.; Nayfeh, Ali H. (American Physical Society, 1982-10-01)The interaction of a diatomic molecule with two near-resonance laser fields is investigated with the use of a one-dimensional anharmonic oscillator model. Our study shows that, over a certain range of intensity of one of the laser fields, induced quenching of the absorption takes place.
- Optical resonance of a two_level atomic systemNayfeh, Munir H.; Nayfeh, Ali H. (American Institute of Physics, 1976)The method of multiple scales is used to derive a solution of the damped optical Bloch equations of a two_level atomic system due to a strong pulsed field. The time dependence of the oscillations of the atomic inversion influenced by detuning and power broadening is found. The population inversion consists, in general, of three terms: a quasisteady term, quasisteady term that decays with time, and an oscillatory term that also decays with time. In the limit of constant fields, the solution of Torrey for damped systems and that of Rabi for undamped systems are recovered. For an adiabatic switching of the field, the solution for undamped systems reduces to that of Crisp in the adiabatic following limit. An equation describing the field envelope is derived for an arbitrary amount of detuning. At exact resonance, this equation reduces to a pendulum equation, in agreement with previous analyses.
- Population difference of two_level atomic system due to a running pulsed fieldNayfeh, Munir H.; Nayfeh, Ali H. (American Institute of Physics, 1975)The method of multiple scales is used to derive an expression for the population difference in an absorbing atomic system due to a running pulsed field. The main contribution to this expression comes from a quasi_steady_state part which has the same functional form as the hole produced by a continuous running field, except that the saturation parameter contains the time dependence of the field. The expression includes also an oscillatory term and a quasisteady term, which decay with a rate that is equal to the inverse of the lifetime of the levels.