Atomic and molecular continuum states may be structured by embedding a bound state into a previously unstructured continuum by a dressing interaction. Autoionizing resonances, in which a high lying discrete state is mixed by configuration interaction into a photoionization continuum, is the best known example in atomic physics. We discuss the process by which a dressing laser can embed a low-lying atomic state into a flat continuum to produce a tunable resonance of adjustable width. Such laser-induced continuum structures (LICS) behave in many ways like autoionizing states. We discuss how such states are formed and how they are probed in photoionization. Saturation properties, including the formation of stabilized dressed states and consequent population trapping, are reviewed. The effects of laser phase fluctuations on the interference phenomena responsible for LICS are included in both semiclassical Wiener-Levy and fully-quantum mechanical theories of multiplicative stochastic processes. We demonstrate how the laser fluctuations can lead to a dephasing of the LICS process and a destruction of population trapping, although these may be restored if the dressing and probing lasers have mutually correlated fluctuations. We also show that additional photoionization rates induced by strong dressing and probe laser fields can cause the population trapped in otherwise stable dressed states to decay away. Finally we discuss the complicating effects of competing transitions, laser pulse shapes and so on of relevance to the experimental observation of LICS.

We use the “virtual source” technique to calculate the low order modes of a confocal unstable optical resonator. We then verify numerically the biorthogonality properties of these modes and calculate the excess noise factor and its dependence upon the effective Fresnel number.

The dynamics of a nonlinear dual-channel directional coupler are studied numerically using a two-dimensional beam propagation method. The results are in good agreement with those of Jensen, which were based on the analytical solution of a pair of coupled-mode equations.

We examine the role of laser phase in multiphoton excitation of atomic transitions. Closed loops in excitation linkages create interfering channels which depend on atomic and laser phases. Such phase-dependent dynamics suggest the use of these transition linkages as atomic interferometers in which states can be decoupled (and population trapped). We show how phase and amplitude measurements are possible in three- and four-level atomic dynamics.

A time-development operator technique is used to describe the intense-field excitation of three-level atomic systems by laser pulses of arbitrary shape. The pulses are divided into small elements for which the time-development is described using the first term in the Magnus expansion. The effects of pulse shapes, detunings, atomic decays and Doppler widths can be included in the analysis. We demonstrate the sensitivity of the dressed three-level atom state populations, Rabi oscillations, population trapping and Autler-Townes splittings on laser pulse shapes.

The authors examine the Doppler profile of a collimated effusive atomic beam for two situations of experimental interest. First, they show that there is an advantage in making the source and collimating slit of comparable size. Secondly they discuss the distribution along a line of sight which is not normal to be beam axis. They compare the predictions with some preliminary experiments.

The authors consider the resonant excitation of the 3868 cm-1 J=3 to 26558 cm-1 J=2 transition in uranium. An experiment has already been done by Scarl et al. (1981) which measures the upper-state population as a function of laser intensity. The authors re-analyse these data taking proper account of the laser's temporal pulse shape. The effect of the laser bandwidth is also included in a novel way. They find a fit to the data which gives different values for the physical parameters from those found by Scarl et al. and draw some general conclusions for experiments of this type.