We used the combined sinusoidal and short-lived weak-pulsed loss modulation techniques to investigate nonlinear dynamics in a cw ${\mathrm{CO}}_2$ laser. The effects of discrete phase and amplitude optical switchings and noncritical slowing down have been demonstrated experimentally. Possible applications of these effects for controlling of temporal and transverse structure of laser intensity are discussed.

Relativistic ionization rates and related phenomena are calculated for ground-state hydrogen atoms in the presence of a circularly polarized electromagnetic field. A Dirac formalism is used, with spin effects fully included. A primary purpose of this work is to explore the effects of relativity on atomic strong-field stabilization. A wide range of frequencies is covered, and in all cases relativistic effects first dampen the stabilization phenomenon as the field intensity increases, and then strongly enhance it in the intensity domain where the ponderomotive potential exceeds the electron rest energy. Relativistic effects can produce major changes in the photoelectron energy spectrum, but perhaps the most easily observable effect is the major shift that can occur in the photoelectron angular distribution.

The behavior of spatial solitons in coupled planar optical waveguides is investigated. A full derivation of the appropriate coupled nonlinear Schrödinger equations is given that includes all the nonlinear cross-phase modulation terms. The dynamics of the spatial solitons are developed using the average variational method of Whitham $[—Linear and Nonlinear Waves (Wiley, New York, 1974)]. The main problems addressed concern spatial soliton beam displacement, beam switching, and a few stability problems. Significant mathematical progress has been made, which is also verified by accurate numerical simulations.

It is found that in an externally kicked Jaynes-Cummings model the transient squeezing of the field can be sustained for longer times as compared with the usual dynamics.

We show that Λ three-level atoms interacting with two coherent light fields tuned close to two-photon or dark resonance behave as a saturable dispersive nonlinearity. If one of the light fields is allowed to resonate within an optical cavity the quantum noise in a quadrature of the output light can be almost completely suppressed. As no dynamic retuning of the cavity is required to achieve noise reduction and cold atomic media are readily available in traps which conform in essence to the proposed configuration, an experimental realization would seem within reach.

This paper describes our recent x-ray laser spectral linewidth measurements and discusses the consequences of these measurements. The experiments observed the 206.38- and 182.45-Å laser transitions in neonlike selenium using an extremely high-resolution soft-x-ray spectrometer, and measured the spectral linewidths and relative spectral intensities of the laser lines from amplifiers of varying lengths. The data allow the intrinsic (unamplified) linewidths of the 206- and 182-Å lasers to be extrapolated as 50 and 35 mÅ, respectively. The intrinsic spectral width of the 206-Å laser is somewhat greater than the predicted 43-mÅ Voigt-profile width based on calculated transition rates and on the expected ion temperature in the plasma, and while the number of data points obtained with the 182-Å laser is small and a conclusive comparison with calculations is not possible, the extrapolated intrinsic linewidth of this laser is clearly consistent with the predicted 37-mÅ Voigt-profile width and is not significantly broader or narrower than expected. The data also show significant gain narrowing of both lines with increasing amplifier length and show no significant rebroadening of the 206-Å laser in long, saturated amplifiers. We discuss line broadening and line transfer calculations we have performed which show that the saturated 206-Å laser line transfer behavior can be treated homogeneously due to non-negligible homogeneous lifetime broadening contributions, which significantly reduce inhomogeneous Doppler saturation rebroadening, and due to collisional redistribution rates which are large enough in any case to homogenize the otherwise inhomogeneous Doppler contributions. We also discuss the implications of these results with regard to earlier suggestions that Dicke narrowing effects could play a significant role in determining the intrinsic line profiles of these laser transitions, and we conclude that Dicke narrowing effects are not likely to be significant for either laser.

We study the behavior of two quantized fields interacting with atoms in a coherent population-trapped state. It has recently been shown that such a system generates fields with matched envelopes as well as matched photon statistics. These effects have an important consequence: the matching of any excess noise input at the two channels of the system. We explicitly show the generation of correlated excess noise by a population-trapped atomic system and how this effect may be used to suppress the excess noise and enhance the carrier-to-noise ratio of optical sources.

The evolution operator for an arbitrary spin system in an arbitrary time-varying magnetic field is disentangled into the rotation operator; consequently, the time-ordering problem is shifted into solving the Euler geometric equations. Some realistic transformations are proposed in order to find their analytic solutions. The probabilities and phases characterizing state transitions are also analyzed.

This paper presents a direct one-step and real-time holographic method for the comparison of two diffusely scattered wave fields originating from two random rough surfaces. The possibility of comparing two random rough surfaces by a straightforward real-time holographic procedure adjoins holographic interferometry with a wide range of application possibilities.

Using the q analog of the Holstein-Primakoff boson realization of the su(2) generators, we show that a type of q-deformed binomial state that corresponds to the Heine distribution can be identified as an su(2${)}_{\mathit{q}}$ coherent state. This fact is a q extension of the fact that the ordinary binomial state is a particular su(2) coherent state when the Holstein-Primakoff transformation is employed.

We consider in this paper the quantum limits for measurements on macroscopic bodies which are obtained by employing the concept of decoherence coming from an analysis of the quantum mechanics of dissipative systems. Two cases are analyzed, the free mass and the harmonic oscillator, and for both system we compare our approach with previous treatments of such limits.

The complex-scaled (r→${\mathit{re}}^{\mathit{i}\mathrm{\theta }}$) Stark Hamiltonian of hydrogen is diagonalized with a B-spline basis. Accurate complex energies of low-lying resonances are obtained for a wide range of electric-field strength (from 0.03 to 2.0 a.u.). The high accuracy is attributed to the good stationarity behavior of θ trajectories with a well-adjusted B-spline basis.

Laser-rf double-resonance spectroscopy of ${}_{}{}^{183}{}_{}{}^{}\mathrm{i}$, an isotope of the most refractory element, has been carried out using an Ar-ion sputtering atomic-beam source; the same technique has been applied to ${}_{}{}^{181}{}_{}{}^{}\mathrm{i}$, another highly refractory element. Hyperfine-interaction constants for the 5${\mathit{d}}^4$6${\mathit{s}}^2$ ${}_{}{}^5{}_{}{}^{}$${\mathit{D}}_2$ state in ${}_{}{}^{183}{}_{}{}^{}\mathrm{i}$ and the ground state 5${\mathit{d}}^3$6${\mathit{s}}^2$ ${}_{}{}^4{}_{}{}^{}$${\mathit{F}}_{3/2}$ in ${}_{}{}^{181}{}_{}{}^{}\mathrm{i}$ have been determined with an order of magnitude better precision than achieved for these refractory elements.

Elastic scattering of electron on positronium below the Ps (n=2) threshold is studied by directly solving the modified Faddeev equations in the total-angular-momentum representation. Resonant behavior of phase shifts near the threshold, due to double-excited states of the (${\mathit{e}}^{\mathrm{-}}$${\mathit{e}}^{\mathrm{-}}$${\mathit{e}}^{+}$) system, is obtained. Estimated positions of the resonances are in good agreement with previous results of a complex-coordinate rotation method [Y. K. Ho, Phys. Lett. 102A, 384 (1984) and references therein].

A general analytical formula is proposed to estimate long-range two-electron exchange interactions in the framework of an asymptotic method for atoms with open shells of any angular type as well as for diagonal and nondiagonal cases. Using the computer algebra language maple v, formulas have been derived for open valence shells of s, p, d, and f types.

An Ar target to which Cs vapor could be added, excited by a pulsed beam of 100-MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ ions, was studied as a prototype ion-atom charge-transfer system for pumping short-wavelength lasers. Low-velocity ${\mathrm{Ar}}^{2+}$ ions were efficiently produced; a huge increase in the intensity of the Ar ii 4d-4p spectral lines was observed when Cs vapor was added to the argon. This observation is explained by a selective charge transfer of the Cs 6s electron into the upper levels of the observed transitions. A rate constant of (1.4±0.2)×${10}^{\mathrm{-}9}$ ${\mathrm{cm}}^3$/s for the transfer process was determined.

We present an internally consistent theory of amplification near the minimum of the absorption profile of autoionizing states, with a quantitative application to calcium. We have included a completely specified three-photon pumping, and have obtained quantitative results for the gain that reveal certain unusual aspects of this system. Our results and their extensions are also discussed in the context of present-day experimental possibilities.

Exact results show that two cooperative atoms driven by a laser and damped by the normal vacuum may eventually end up as pure states in the presence of static dipole-dipole interaction.

The even and odd coherent states are generalized for the multimode case. The explicit forms for the photon distribution, Q function, and Wigner function are derived. In particular, it is shown that for the two-mode case there exist strong correlations between these modes, under certain conditions, which are responsible for two-mode squeezing in the case of even coherent states.

A commonly used numerical technique for calculating the harmonic spectrum emitted by an atom exposed to an intense laser pulse is the direct integration of the Schrödinger equation. We compare the spectra calculated using two different models. The first is in one dimension with an approximate hydrogenic soft-core potential and the second is in three dimensions with a Coulomb potential. We use realistic laser pulse conditions (100 fs,800 nm) and intensities at which there is significant ionization, leading to a saturation of the harmonic-generation process. Although the ionization rates in the two models differ, the harmonic spectra and the positions of the cutoff are remarkably similar. Only a relatively small number of angular momentum states is needed in the three-dimensional calculation to give a reliable estimate of the cutoff, even for intensities at which there is strong ionization.