We demonstrate that the reciprocal-space Hamiltonian method for quantizing the electromagnetic fields in a dispersive dielectric medium leads to inconsistencies when applied to the cases of plasmon polaritons and coupled phonon-plasmon polaritons. In particular, we show that the use of the standard expressions for the dielectric functions in these two cases leads to the violation of the Huttner-Barnett velocity-ratio sum rule and, hence, to the breakdown of the equal-time canonical field commutation relations. We show that correct behavior is recoverable after the dielectric functions are appropriately regularized. Regularization effectively leads in each case to the introduction of an additional transverse low-frequency polariton branch. This is sufficient to rectify the theory and there is no need to invoke the presence of the longitudinal modes. The theory is illustrated with reference to the coupled phonon-plasmon polaritons of Si-doped GaAs. © 1996 The American Physical Society.

Lai and Haus [Phys. Rev. A 40, 854 (1989)] recently introduced the use of a photon configuration-space wave function to analyze optical soliton propagation in a fiber. This is of interest as photon wave functions have long been the source of controversy; the work of Lai and Haus was the first to demonstrate that they could be of use in quantum optics. The systematic reduction of photon configuration-space wave functions directly from QED was recently carried out, which puts the general approach on solid ground. Here we apply the photon configuration-space approach systematically to the dynamics of the soliton center of mass and phase spread, and to squeezing in optical fibers. The predictions of the configuration-space model agree with results from the quantum field theory linearization models, which provide an important benchmark for the new approach. The configuration-space model leads ultimately to a description of the soliton as a quantum object that obeys free particle dynamics in relative position and phase. Phase squeezing appears in the configuration-space model as a consequence of free particle dynamics following initial phase localization due to the use of an initial classical soliton state. © 1996 The American Physical Society.

An analytic solution of the Bloch equation is presented using a class of asymmetric complex functions as a driving function. These may involve both amplitude and frequency modulation functions. Analytic solutions that have been previously derived include the amplitude modulated (‘‘real’’) hyperbolic secant pulse and its asymmetric generalization in addition to the complex sech/tanh pulse. The solution presented in this paper contains all of these as particular cases. The solution in its complex form is closely associated with an adiabatic fast passage experiment and renders robust magnetization inversion provided the rf amplitude exceeds a certain threshold. © 1996 The American Physical Society.

An extension of the standard Raman-coupled Jaynes-Cummings model has been made to include atomic external effects due to quantization of atomic motion. The collapse-and-revival phenomena in population inversion and in atomic motion, the velocity-selective population and their relation for a motion-quantized atom are given on the basis of a fundamental constant characterizing the interaction strength between the field modes and the atomic internal and external states. This study reveals how the initial statistics of atomic momentum affect the atomic internal dynamics and how those of the fields affect the atomic external dynamics through the atomic internal states. An exact expression for the time evolution of the density operator has been given for two fields and the center-of-mass motion initially in coherent states and in an arbitrary superposition of atomic momentum eigenstates. The statistics of atomic external and internal quantities such as the radiation force and the atomic momentum are given. © 1996 The American Physical Society.

A rigorous density-matrix approach has been applied to the interaction between an autoionizing system and electromagnetic radiation. The balance equations have been derived and analytical expressions for the inversionless lasing threshold and saturation output have been obtained. Using the intersubband transitions as an example, the potential performance of the inversionless laser has been analyzed and found to be inferior to that of the conventional laser. © 1996 The American Physical Society.

We study the two-photon excitation rate and the spectrum of a three-level atom in the Ξ configuration interacting with a resonant cavity mode which is coupled to a broadband squeezed vacuum through its input-output mirror. We show that the optical Bloch equations in the cavity environment are formally identical to these in free space but, in the bad-cavity limit, with cavity-modified parameters describing the injected squeezed vacuum. It is shown that the two-photon excitation rate (which is proportional to the upper-level population) has two components, one depending linearly and the other quadratically on the squeezed photon number N, in excellent agreement with experiment [Georgiades et al., Phys. Rev. Lett. 75, 3426 (1995)]. The presence of the term quadratic in N is entirely due to the effectively imperfect correlation of the squeezed photon pairs in the bad cavity. We also find that the two-photon excitation spectrum (as measured by the fluorescent emission from the upper level to the intermediate level) exhibits an extremely narrow peak at line center, under appropriate choices of the bad-cavity parameters. All these results are independent of the squeezed phase. © 1996 The American Physical Society.

The decay of an excited two-level atom in a cavity with mirrors of finite transmittivity is studied with the help of a generalized multimode master equation that has been established recently. The time evolution of the decaying atom is obtained by accounting for the interaction with infinitely many quasimodes. The analytical and numerical results are compared with those of the standard multimode master equation and of a universe-mode approach. © 1996 The American Physical Society.

We report results of the study of soft-x-ray amplification in a discharge-created plasma under an externally applied axial magnetic field. This technique is observed to improve the uniformity and divergence of the beam of a 46.9-nm discharge-pumped Ne-like Ar soft-x-ray amplifier by decreasing the plasma density gradients at the time of lasing. At the optimum strength of 0.15 T, the magnetic field also causes an increase in the laser beam intensity. At higher fields the Zeeman effect is found to contribute to line broadening, decreasing the laser output. © 1996 The American Physical Society.

The constrained minimization independent-fermion kinetic-energy kernel, ${\mathrm{\delta }}^2$${\mathit{T}}_{\mathit{s}}$[ρ]/δρ(r)δρ(${\mathbf{r}}^{\prime }$), has a zero mode for all ρ(r), while it is non-negative for ρ(r) noninteracting v representable. © 1996 The American Physical Society.

The macroscopic electric field resulting from the space charge produced in electron-impact experiments has been characterized by using secondary electrons of well-defined energy (e.g., Auger or autoionizing electrons) as a probe. It is shown that the measurement of the kinetic-energy shifts suffered by secondary electrons is a suitable tool for the analysis of the self-generated electric field in a low-density plasma. © 1996 The American Physical Society.

Fast positive ions and atoms with energies ranging from some 100 eV to 100 keV are scattered under a grazing angle of incidence from a clean and flat (100) surface of a monocrystalline KI sample. We observe for halogen projectiles an almost complete negative-ion conversion, i.e., negative-ion fractions up to 98.5%. Our data show a characteristic dependence on the projectile velocity, which provides important additional information on the mechanisms of formation of negative ions in the scattering from the surface of an insulator. © 1996 The American Physical Society.

We have analyzed the recently measured single, double, and triple ionization of Ar by strong laser pulses in terms of an independent-electron model. An excellent fit to the highest intensity data is obtained in terms of two single-electron ionization probabilities that correspond to the initial 3p bound orbitals being in the m=0 or ±1 substates. Their relative magnitudes are understood in terms of the tunneling of electrons that are in differently oriented bound orbits, and they both exhibit the expected approach to unity as the limiting over-the-barrier electron ejection is realized. The n-electron ionization probabilities go through maxima and crossings at the highest intensities that are well described by the independent-electron model. © 1996 The American Physical Society.

We have measured the locations and widths of the avoided level crossings between (n+3)s states and n,k Stark states in Rydberg Rb atoms with principal quantum numbers n between 16 and 25. We use two-step laser excitation to excite (n+3)s states in the presence of an electric field and observe a change in the number of atoms driven to higher-lying states by blackbody radiation as the electric field is tuned through the avoided level crossings. We have measured both the positions and widths of the avoided crossings. © 1996 The American Physical Society.

We report the results of our simulations of the interaction of a laser pulse with a three-level atom. A coupling of the upper level to the continuum is modeled by introducing an irreversible loss. Result shows that one can suppress the ionization by choosing the proper shape of the laser pulse. © 1996 The American Physical Society.

The determination of the harmonic oscillator wave function from position distribution and its time derivative is investigated. Quite simple definitive equations result for the expansion coefficients of the wave function in the Fock basis and yield a unique solution. The effect of a finite spatial resolution of the measurements is taken into account. © 1996 The American Physical Society.

Spatial correlation effects are analyzed in a laser near and below its threshold of oscillation by integrating the modifications in the correlation function of intensity fluctuations and related parameters. The pump parameter of the laser is shown to depend on the field spatial coherence which arise due to transverse-mode structure of the laser field implying modifications of the spectrum in the time domain. © 1996 The American Physical Society.

The radiation reaction force due to individual emitters of a homogeneously broadened gain sheet is calculated from the multimode quantized electromagnetic field. This force can be placed in the dipole moment operator equation of motion, and takes a form similar to superradiance. A small correction factor in the laser rate equations for an optical gain sheet placed in a large dimension cavity is derived. For small cavity systems, such as the Fabry-Pérot microcavity, the correction factor may be increased. © 1996 The American Physical Society.

We calculate the lifetime of the vacuum trapping state in a micromaser, using both the Monte Carlo wave-function method and an analytic approximation, and show it to be a rapidly changing function of the average number of atoms in the cavity, when this number is much smaller than one. Our method leads to a realistic simulation of experiments, allowing for different field profiles, temperatures, and atomic velocity spreads. © 1996 The American Physical Society.