We have investigated the two basic types of Hanle fluorescence spectra, distinguished by the direction of observation, from a V-type atom with a ${\mathrm{J}}_{\mathrm{g}}$ =0⇆${\mathrm{J}}_{\mathrm{e}}$ =1 transition excited by a linearly polarized laser. In the absence of a magnetic field to lift the Zeeman degeneracy of the sublevels, the incoherent fluorescence spectrum ${\mathrm{G}}_{\mathrm{X}}^{\mathrm{inc}}$(ω) is dark for all Rabi frequencies, while the incoherent fluorescence spectrum ${\mathrm{G}}_{\mathrm{Y}}^{\mathrm{inc}}$(ω) exhibits a single peak for small Rabi frequencies and a Mollow-like triplet for large Rabi frequencies. However, if a magnetic field is applied, the incoherent spectra are composed, in general, of five peaks. When ${\mathrm{\omega }}_{\mathrm{B}}$ ≪Ω, the incoherent spectrum ${\mathrm{G}}_{\mathrm{X}}^{\mathrm{inc}}$(ω) has four peaks, while ${\mathrm{G}}_{\mathrm{Y}}^{\mathrm{inc}}$(ω) has a Mollow-like triplet, and the integrated area (i.e., the fluorescence intensity) under the spectrum ${\mathrm{G}}_{\mathrm{X}}^{\mathrm{inc}}$(ω) is much less than that of ${\mathrm{G}}_{\mathrm{Y}}^{\mathrm{inc}}$(ω). When ${\mathrm{\omega }}_{\mathrm{B}}$ ≫:Ω, both incoherent spectra have a two-peak structure similar to that of a two-level atom far off resonance, but the integrated area under the spectrum ${\mathrm{G}}_{\mathrm{X}}^{\mathrm{inc}}$(ω) is much greater than that of ${\mathrm{G}}_{\mathrm{Y}}^{\mathrm{inc}}$(ω). When ${\mathrm{\omega }}_{\mathrm{B}}$ =Ω≫:γ, both spectra have a similar five-peak structure, and the same integrated area. The results obtained are interpreted in the dressed atomic state representation. In the strong-field limit, the secular approximation is invoked, and analytical expressions of the resonance fluorescence spectra are derived which demonstrate the dependence of the peak heights and widths of the resonance fluorescence spectra on the intensities of the magnetic and linear polarized laser fields in a more transparent way.

Two aspects of the relativistic version of the Einstein-Podolsky-Rosen-Bohm (EPRB) experiment with massive particles are discussed: (a) a possibility of using the experiment as an implicit test of a relativistic center-of-mass concept, and (b) influence of the relativistic effects on degree of violation of the Bell inequality. The nonrelativistic singlet state average 〈ψ|a⋅σ⊗b⋅σ|ψ〉=-a⋅b is relativistically generalized by defining spin via the relativistic center-of-mass operator. The corresponding EPRB average contains relativistic corrections which are stronger in magnitude than standard relativistic phenomena such as the time delay, and can be measured in Einstein-Podolsky-Rosen-Bohm-type experiments with relativistic massive spin- particles. The degree of violation of the Bell inequality is shown to depend on the velocity of the pair of spin- particles with respect to the laboratory. Experimental confirmation of the relativistic formula would indicate that for relativistic nonzero-spin particles centers of mass and charge do not coincide. The result may have implications for quantum cryptography based on massive particles.

The formulation of the evolution operator for the multiphoton Jaynes-Cummings interaction in the decomposition form is presented, in terms of the SU(2) rotation transformation proposed by the present author [J. Mod. Opt. 39, 2209 (1992)]. The study of the dynamical evolution of the photon statistics for the case of intensity dependent coupling with m-photon atomic transition exhibits a number of novel features (sub-Poissonian and oscillatory distributions). It is shown that for m=1 the field distribution oscillates exactly in a periodic sequence without the limitation of the large mean photon number n-bar, and that for m=2 the oscillatory distributions emerge at one-quarter and three-quarters of the revival time for the initially high boson excitation regardless of the initial condition of the atomic state.

We show that the three degenerate modes of family q=2 in a ${\mathrm{CO}}_2$ laser with high cylindrical symmetry produce a rotating pattern in which frequency degeneracy is removed. The rotation frequency is determined by the nonlinear interaction with the atomic medium. This is an example of the antifrequency locking phenomenon typical of class-B lasers. The measured rotation frequencies for different values of the discharge current agree well with theoretical predictions.

We discuss the condition under which a pair of closely lying levels, when coupled to a fourth level via a single-laser field, exhibit population trapping without decay to a lower level. In the discussion, the decay between the pair and the fourth level is taken into account. When the fourth level is lower than the pair, the condition for population trapping in the pair can be satisfied under arbitrary laser intensity by adjusting the laser detuning. When the fourth level is above the pair, population trapping in the pair is impossible when the decay from the fourth level to the pair is included. The influence of the decay between the pair and the fourth level on the spontaneous spectrum from the pair to the lower level is also studied.

Using a weakly nonlinear analysis, we study the behavior of a homogeneously broadened laser in the vicinity of the second threshold. We show that the dynamics is described by a complex Ginzburg-Landau equation coupled to a Fokker-Plank equation. Although the cubic term of the Ginzburg-Landau equation is destabilizing for all parameter values, bounded solutions exist because of the strong nonlinear dispersion ('dispersive chaos'). A careful numerical study of the original Maxwell-Bloch equations is also carried out to investigate the role played by off-resonant solutions.

Theory and experiment are presented that suggest a new avenue for designing femtosecond temporal probes in which multiple spatially overlapped noisy (nontransform limited) quasi-cw laser light beams are tailored in a controllable fashion by dispersion. The generation of femtosecond probes is demonstrated experimentally by combining the output from two distinct nanosecond pulsed dye lasers to form a single ``tailored'' beam having a double-peaked spectral density corresponding to the superposition of emission spectra of each of the dye lasers. The interferograms produced from this single beam display features on the time scale significantly shorter than the autocorrelation time of either of the component beams alone. The theory, incorporating controllable dispersion effects, correctly captures the interferometric patterns seen in noisy light two-color frequency summing experiments and is general enough to treat experiments involving the spatially combined emission of an arbitrary number of light sources. Concepts both of noisy light spectroscopy and of amplitude modulated pulse shaping are applied. Applications of such tailored noisy light sources to wave-packet preparation and even photochemical control may be anticipated.

We examine the response of a coherently driven two-level atom interacting with a broadband squeezed vacuum to a probe beam of arbitrary intensity. The equations of motion for the reduced density matrix elements are numerically solved by nonperturbative matrix inversion methods. For large driving intensities, the absorption spectrum exhibits a number of multiphoton absorption peaks with increasing probe strength in a standard vacuum and in a squeezed vacuum with small photon numbers, while the multiphoton absorption peaks are wiped out for large squeezed photon numbers. Strong gain without inversion at line center can be obtained in the presence of the squeezed vacuum when the probe strength does not exceed the driving one. The absorption spectrum is phase sensitive. We also find the presence of remarkable, very narrow structures at line center. In general, the spectrum is symmetric when Φ=0 and π; otherwise, it is asymmetric and displays a dispersivelike profile at line center.

We investigate systems of few harmonic oscillators with mutual nonlinear coupling. Using classical trajectories—the solutions of Hamiltonian equations of motion for a given nonlinear system—we construct the approximate quasiprobability distribution function in phase space that enables a quantum description. The nonclassical effects (quantum noise reduction) and their scaling laws can be so studied for high excitation numbers. In particular, the harmonic oscillators represent modes of the electromagnetic field and the Hamiltonians under consideration describe representative nonlinear optical processes (multiwave mixings). The range of the validity of the approximation for Wigner and Husimi functions evolved within the classical Liouville equation is discussed for a diverse class of initial conditions, including those without classical counterparts, e.g., Fock states.

The behavior of diffraction losses in multiapertured laser resonators is theoretically and experimentally investigated. In the case of geometrically unstable resonators, it is shown that the combination of several apertures whose diameters have been independently optimized to reduce the laser diffraction losses leads to a still lower value for these losses. This puzzling fact is verified experimentally for a negative branch unstable resonator laser containing up to five intracavity apertures. In the case of geometrically stable resonators, it is shown that the introduction of a first intracavity aperture that selects the fundamental mode leads to modifications of the fundamental mode shape which, besides being relatively small, are sufficient to make the diffraction losses oscillate with the diameters of the following extra intracavity apertures. In particular, the diameters of these apertures can be optimized to reduce the diffraction losses below the value obtained with the first aperture only. These predictions are experimentally verified in the case of a dynamically stable cavity high power Nd:YAG (yttrium aluminum garnet) laser. In all cases, the calculations based on the Huygens-Fresnel principle exhibit a good agreement with the experimental results.

We investigate the behavior of a two-level atom in a multimode cavity driven from the side by a time-dependent field. The time-dependent fields we have looked at are (i) pure amplitude modulated, (ii) pure frequency modulated, (iii) single sideband, and (iv) general three-mode fields. Each of these fields results in two (for the single-sideband case) or three modes separated by the modulation frequency. We find that when the driving field mode spacing is a multiple of the cavity mode spacing, the multimode cavity field created by the driven two-level atom becomes exactly 180° out of phase with the external driving field in steady state. This results in a zero net field at the position of the atom and, hence, the atom remains unexcited regardless of the strength of the external driving field. This is very reminiscent of the field-induced transparency effect as described by Cardimona et al. [J. Phys. B 15, 55 (1982)] in which the various dipole transitions of a multilevel atom dressed by a coherent field are driven 180° out of phase with each other, producing a zero net fluorescence. We also show that, in the limit of an infinite cavity, the multimode equations reduce to the neoclassical equations of Stroud and Jaynes [Phys. Rev. A 1, 106 (1970)].

A generalization to the complex plane of Einstein's addition law of velocities is used to calculate energy levels and wave functions at any place in quantum potentials of arbitrary shape. Some examples are presented (resonant tunnel effect, truncated harmonic oscillators). A comparison with the usual poles method is also discussed.

In this work a method is established for isolating effects due to single or successive two-body scatterings from those arising from three-body coupling in a three-particle Coulomb system above the complete breakup threshold. It is shown that three-body interactions decide the weighting of individual scattering amplitudes, and hence, determined the interference pattern of these amplitudes. In addition, the method is applied to the analysis of low-energy, electron-impact ionization of atomic hydrogen in the coplanar asymmetric energy-sharing kinematic. The ionization dynamic leading to the measured cross section is unraveled. It is demonstrated that, unlike the situation at higher energies, at low incident energies the cross section is largely decided by interferences indicating a strong three-body coupling.

The asymptotic limits of the leading term of the energy shift between a pair of molecules due to exchange of three virtual photons are calculated using nonrelativistic quantum electrodynamics. In the electric dipole approximation, this discriminatory interaction depending on the handedness of each species, corresponds to the near- and far-zone energy shifts between two hyperpolarizable molecules. The far-zone result, exhibiting an ${\mathrm{R}}^{\mathrm{-}11}$ dependence on intermolecular separation is compared with far-zone limits of higher multipole polarizable interaction energies arising from a two-photon exchange.

Continuum x rays originated from radiative electron capture into continuum states (RECC) of relativistic ${\mathrm{Ne}}^{10+}$ ions have been observed. It has been found that the intensities of x rays decrease as their energy increases and the observed spectra show a clear edge which corresponds to the maximum energy transferred to free electrons under energetic projectile-ion collisions. The edge becomes dramatically sharp as the incident projectile energy decreases from 290 to 75 MeV/amu, indicating that the cross sections for RECC sharply increase at low projectile energies, which is in agreement with the theoretical expectation.

A method has been developed to calculate the integral cross sections from the measured generalized oscillator strengths that are fitted by a Fourier expansion. The method has been applied to the e-Xe and e-${\mathrm{N}}_2$ scattering problems. Excellent agreement has been obtained with existing measured values for the transitions to ${5\mathrm{p}}^5$ ${(}^2$ ${\mathrm{P}}_{3\mathrm{/}2}$ )6s and ${5\mathrm{p}}^5$ ${(}^2$ ${\mathrm{P}}_{1\mathrm{/}2}$ )6s of Xe at 100 and 500 eV. For the vibrational states, v=1–4, of the ${\mathrm{b}}^1$ ${\mathrm{\Pi }}_{\mathrm{u}}$ electronic state of ${\mathrm{N}}_2$ at 300 eV, good agreement with the data calculated by the Lassettre expansion has also been achieved.

Total quantum mechanical cross sections for photodetachment of ${\mathrm{H}}^{\mathrm{-}}$ in parallel E and B fields are examined both analytically and numerically to extract information which has a classical interpretation, thereby complementing recent classical and semiclassical periodic orbit studies.

The revival structure of Stark wave packets is considered. These wave packets have energies depending on two quantum numbers and are characterized by two sets of classical periods and revival times. The additional time scales result in revival structures different from those of free Rydberg wave packets. We show that Stark wave packets can exhibit fractional revivals. We also show that these wave packets exhibit particular features unique to the Stark effect. For instance, the wave functions can be separated into distinct sums over even and odd values of the principal quantum number. These even and odd superpositions interfere in different ways, resulting in unexpected periodicities in the interferograms of Stark wave packets.

We derive a set of cavity-modified Maxwell-Bloch equations for a two-level atom in a cavity driven by a coherent field from the single-atom Fokker-Planck equation in the bad-cavity limit. These equations have the same form as the Maxwell-Bloch equations for a two-level atom in free space interacting with a coherent field. The presence of a cavity is reflected in three cavity-modified parameters: decay rate ${\gamma }_{\mathrm{eff}}$, Rabi frequency ${\mathrm{\Omega }}_{\mathrm{eff}}$, and detuning ${\mathrm{\Delta }}_{\mathrm{eff}}$. We show that the cavity-modified Maxwell-Bloch equations provide an easy way to study cavity-modified spontaneous emission, cavity-induced radiative energy level shifts, and vacuum Rabi splitting.

We present two-dimensional, high-resolution, spatial images of the 196-Å laser emission from the output aperture of a neonlike germanium laser which is created by illuminating a slab target with a series of short 100-ps pulses from the Nova laser. Simulations of the gain which are propagated through the plasma density gradients to calculate the spatial distribution of the laser intensity are compared with the experiments and show good agreement. The importance of refraction in the propagation calculation manifests itself in the laser intensity peaking 150 μm from the target surface, even though the gain peaks 50 to 60 μm from the target surface.