The quantization of the electromagnetic field between moving boundaries in four-dimensional spacetime is studied. We consider the particular case of a field confined between two infinite conducting plates moving with constant relative velocity. It is shown that this motion produces squeezed states and leads to the production of particles at the expense of the Casimir energy. Analytic formulas for the Bogoliubov and the squeezing coefficients are obtained. The energy momentum tensor and its spectrum are evaluated from the field correlations.

A method is presented for theoretically investigating the properties of a one-atom micromaser with stationary non-Poissonian pumping. The method is based on treating the statistics of the arrival times of the individual pump atoms with the help of the theory of stochastic point processes. Considerable simplification is achieved by assuming the pump statistics to be described by a stationary renewal process. Thus the influence of super- as well as sub-Poissonian pumping with different strengths of correlation between the pump atoms and different correlation decay times may be studied quantitatively. The level-selective statistics of the atoms leaving the cavity is investigated as well as the photon statistics of the cavity field. Moreover, the relation to the other models used in the literature for describing the micromaser pump statistics is discussed. It is found that for sub- (super-)Poissonian pumping, the stationary expectation value of the cavity photon number (which corresponds to its time-averaged value) is larger (smaller) than the conditioned mean photon number that would result from averaging over the number of photons present in the cavity at the time instants immediately before the injection of the individual pump atoms. For Poissonian pumping, both quantities are shown to be equal. The relative standard deviation of the stationary cavity photon number is decreased (increased) for sub- (super-) Poissonian pumping, in comparison to the corresponding values that would result from Poissonian pumping. Moreover, it turns out that for sub- (super-)Poissonian pumping, the normalized coincidence probability density for the detection of the outgoing deexcited atoms is smaller (larger) than the normalized cavity field intensity correlation function at zero time delay. The difference decreases with increasing lifetime of the pump-atom correlations. Finally, the level-selective delayed coincidence probability densities of the outgoing atoms and their waiting-time distributions are found to be affected greatly by the correlation strength as well as the correlation decay time of the incoming pump atoms.

The Jaynes-Cummings model of a two-level atom interacting with a single quantized mode of radiation field is generalized to include the effects of stochastic fluctuations in the atom-field coupling. The coupling coefficient is assumed to fluctuate either in phase or in frequency. The fluctuations are modeled by binary random telegraph processes. Invoking the Markovian property of the telegraph noise, we derive in these two cases an equation for the density operator averaged over the distribution of fluctuations. The solution of this equation is used to study the resulting decoherence effects in the dynamical behavior of the atom and the statistical properties of the field.

We consider the influence of acceleration on the radiative energy shifts of atoms in Minkowski space. We study a two-level atom coupled to a scalar quantum field. Using a Heisenberg picture approach, we are able to separate the contributions of vacuum fluctuations and radiation reaction to the Lamb shift of the two-level atom. The resulting energy shifts for the special case of a uniformly accelerated atom are then compared with those of an atom at rest.

Resonance fluorescence of two two-level atoms driven by a coherent laser field propagating parallel to the interatomic axis is examined, taking into account the dipole-dipole interaction. We show that the number of peaks in the fluorescence intensity depends on the direction of observation with respect to the interatomic axis and on whether the system is driven by a standing-wave or a running-wave laser field. When the system is driven by the standing-wave field the fluorescence intensity shows two peaks and a dip for an observation direction perpendicular to the interatomic axis and three peaks in the direction parallel to it. When the system is driven by the running-wave field only two peaks are observed for the perpendicular direction. We explain these features in terms of the collective states of the system and show that the directional effect can be attributed to the fact that the antisymmetric state of the system does not radiate in the direction perpendicular to the interatomic axis. Photon statistics also demonstrate the directional effect for the standing-wave field. Frequency regimes are found where sub-Poissonian photon statistics occur. Depending on the direction of the observation, a state close to a Fock state can occur for one or two frequencies of the driving field, corresponding to zero-photon-number fluctuations or maximum sub-Poissonian behavior. The fluorescence spectrum is found to depend on the direction of observation and the interatomic separation. For small interatomic separations and a standing-wave driving field the spectrum exhibits seven lines for the perpendicular direction and 13 lines in the direction parallel to the interatomic axis. For the running-wave field the spectrum shows 13 lines independent of the direction of observation. Moreover, we show that for particular interatomic separations dark regimes appear in the spectrum. We discuss the effect of the dipole-dipole interaction on the dark states and explain the spectral features in terms of the dressed-atom model. We also consider the absorption spectrum of a weak probe beam illuminating the two-atom system. We show that apart from a weak dispersion structure, the spectrum shows large peaks as one of the atoms is moved to successive nodes of the field.

The quantum-mechanical problem of bosons, in a square well in one dimension and interacting with a δ function, is analyzed and solved. The resulting Bethe-ansatz wave function is a sum, over the Weyl group of Lie algebra ${\mathit{B}}_{\mathit{N}}$, of nondiffractive waves. The secular equation of the spectrum is obtained and its thermodynamic limit is discussed.

Raman scattering of the Q(1) line in ${\mathrm{H}}_2$ gas was investigated from the spontaneous to the stimulated scattering region using a frequency-doubled Q-switched Nd:YAG laser (where YAG denotes yttrium aluminum garnet). We measured the Raman Stokes energy as a function of the laser power and the radial distribution of the Stokes intensity for the unfocused and the focused Gaussian laser beam. There is good agreement between the experiments and the results of a nonorthogonal mode theory in the region of stimulated Raman scattering. For cell lengths short compared to the Rayleigh range of the laser beam or for Raman cells far from the beam waist, stimulated Raman scattering is described in a good approximation by an adapted plane-wave theory. In the region of spontaneous Raman scattering, the measured dependence on cell length, solid angle, and focusing conditions is not in accordance with the nonorthogonal mode theory, but agrees with the standard theory of spontaneous Raman scattering.

Oscillation conditions for unidirectional ring resonators containing cubic photorefractive crystals are analyzed. The coupling of pump beams to intracavity modes is presumed to occur via the vectorial two-beam coupling in the crystal. It is also presumed that the intracavity field as well as the pump field are composed of two orthogonally polarized components. The solution of slowly varying envelope wave equations in the degenerate and steady-state limit is used to determine the grating action and to derive threshold conditions for both the transmission and the reflection geometry of the wave-mixing process. A number of special cases of wave-mixing coupling constants is considered. Potential applications of two-wave mixing rings in different photorefractive devices, such as optical amplifiers, switches, and logic circuits are discussed.

We present a method for the unambiguous detection of a classically distinguishable coherent superposition state in the vibrational coordinate of a diatomic molecule. The configuration of the state may be observed via the time-dependent spectrum of spontaneous emission from the molecule. The signature of the states in the emission spectra is discussed, as are the practical possibilities for experiments on a realistic molecular system.

Investigations of oscillations in mirrorless lasers are presented for 3391 and 3507 nm in He-Ne and Xe discharges, respectively. It appears that the theory, based on the assumption of intensity saturation of the opposite waves, is only confirmed at the central and end parts of the He-Ne discharge. Stimulated reflection is proposed to explain experimental effects.

The effect of formation of asymptotically stable solitary waves (ASSW) in an amplifying dispersive medium with frequency-dependent linear amplification, nonlinear losses, and nonlinear refractive index is predicted. All the parameters of the ASSW are invariants of the medium. The method developed is based on formalism of the Fokker-Planck equation describing a pulse dynamics in the presence of noise. The stability is proved by Lyapunov’s method. It was found that the ASSW is described by the Euler-Lagrange equation defined by a minimum of the effective potential being the Lyapunov function. It was found that the bright solitary wave is unstable whereas the dark solitary wave is asymptotically stable.

We explore the use of degenerate four-wave-mixing (DFWM) intensity noise fluctuations as a spectroscopic tool for the study of atomic dynamics. Experimental results obtained from the spectral analysis of the intensity noise of the DFWM signal produced by a free running diode laser in a rubidium vapor cell are presented. For low exciting field intensities, the spectra are single peaked with a linewidth comparable to the atomic natural linewidth while at higher intensities a structure devleops revealing the existence of a dynamic Stark effect. The results are compared with numerical simulations of the power spectrum of the DFWM signal produced by a phase-diffusing field incident on two-level atoms.

It is shown that the existence of a time operator in the Liouville space representation of both classical and quantum evolution provides a mechanism for effective entropy change of physical states. In particular, an initially effectively pure state can evolve under the usual unitary evolution to an effectively mixed state.

The effect of light polarization on the growth of second-harmonic generation (SHG) in germanium-doped silica thin-film planar waveguides was investigated. Film-generated SHG produced by input coupled light with transverse magnetic polarization was measured to be over three orders of magnitude larger than that for light with transverse electric polarization. A phenomenological model, based on charge transport induced by photoionization, was used to compute the SHG and was found to agree with the experimental results.

Quantum interference between decay processes from two upper levels, which are coupled by the same vacuum modes to a lower level, have been investigated and its effects on the spontaneous emission spectrum have been studied. The interference can result in spectral narrowing and a black dark line in the spectrum. The population in the upper levels is not a simple exponential decay due to the interference.

The dynamics of the period-doubling chaos of an optically pumped ${\mathrm{NH}}_3$ single-mode ring laser is investigated experimentally and the metric properties of the attractor are calculated for different experimental conditions. Studies of the periodic attractors of the laser are also reported. We show experimentally that the dynamics of the period-doubling chaos and the periodic attractors of the laser is generally more complex than that of the extended Lorenz equations allowing cavity detuning, although, when the influence of pump coherence effects becomes weak, the dynamics of this laser approaches that of the extended Lorenz equations.

We address the physics of pulse propagation, energy flow, and field dynamics as described by Maxwell’s equations. After deriving the form of the Poynting vector for pulses that vary slowly in time only, we show that interference terms nontrivially affect the momentum and the energy density of an electromagnetic pulse that scatters from highly reflective materials. Inside such materials, we conclude that the magnetic- and electric-field amplitudes are strongly out of phase. We then apply our findings to the study of layered periodic structures; specifically, we examine the propagation of apparently ‘‘superluminal’’ pulses. By monitoring the local momentum and energy densities in the structure at all times, we explicitly show that the canonical energy velocity can never exceed the vacuum speed of light c at any point in the crystal.

We show that optical homodyne measurements of coherent states, and of superpositions of coherent states, can be described using the joint photon-number distribution for entangled coherent states. The quadrature-phase distribution interference fringes for superpositions of macroscopically distinct coherent states (the so-called ‘‘Schrödinger cat states’’) are shown to arise from interference in the photon-number distribution for entangled coherent states. The entangled squeezed states are introduced here as squeezed superposition states which are optically mixed with an antisqueezed coherent local oscillator field (squeezing in the other quadrature) at a beam splitter, and we discuss the connection between entangled squeezed states and squeezed-state homodyne detection of squeezed light. Finally the relationship between interference in phase space and fringes in the joint photon-number distribution for the entangled squeezed state is explored.

A correlation-function hierarchy for intracavity quantum optical systems has been derived using nonequilibrium Green function methods. A specific truncation is applied to study nonlinear quantum fluctuations in an optical parametric oscillator near threshold. An analysis of the limitations of the truncation and comparison of its efficiency and accuracy relative to coherent state phase space methods and wave-function simulation methods is made.

The nonlinear Sagnac-loop squeezer at zero group velocity dispersion is analyzed using a finite relaxation time for the Kerr effect. A recently developed theory that avoids the discretization of time is used. A closed form expression for the photocurrent fluctuation level is derived. It is shown that in the linearized limit, Gaussian pulses experience slightly more squeezing when their duration is comparable to the response time of silica. The present treatment indicates that the electronic response time determines the length of fiber beyond which substantial deviations from the linearized theory occur. Contrary to the discretized-time model, the continuous-time theory does not exhibit quantum revivals.