A study is presented of the long-time dynamical behaviour of the degenerate parametric oscillator in the semiclassical and quantum regimes for various initial conditions. It is shown that the eigenstates of the trilinear Hamiltonian lead to the collapse and revival phenomena as well as the novel phenomena of fractional revivals in the photon statistics of the field modes. It is also demonstrated that fractional revivals become more prominent if the pump mode possesses sub-Poissonian statistics.

We investigate the characteristics of the coherent population trapping (CPT) states in a dense medium. We incorporate the local-field effects into the density-matrix equations and numerically integrate the resulting nonlinear equations. We find that the CPT state is essentially unaffected by the local-field effects for all ranges of field strengths; however, states close to the CPT state are sensitive to them. We demonstrate a dispersive behavior near the CPT state in a dense medium besides important asymmetries and shifts of the Autler-Townes peaks in absorption spectra. We also study the effect of local fields on the dynamics before CPT occurs and show that the evolution to the CPT state is delayed due to the local fields. We extend our calculation to analyze lasing without inversion in a dense medium of \ensuremath{\Lambda} systems. \textcopyright{} 1996 The American Physical Society.

A three-level lambda (Lambda) system driven by two coherent fields at the Raman resonance condition evolves to a nonabsorbing eigenstate of the Hamiltonian called the coherent population trapping (CPT) state. We study the various factors dictating the dynamical evolution of the coherencesand the populations to the CPT state. We demonstrate the formation of the CPT state even at low intensities, though it takes much longer to form such a state. For the case of unequal decay rates we demonstrate an interesting sharp dip in the steady-state response of the medium at the Raman resonance condition.

We present a very simple theoretical framework for extracting spectroscopic data on an atom via stochastic probing with a fluctuating laser source. By exploiting the fact that the linear susceptibility contains all the atomic structure information in it, we show that the power spectrum of the fluctuations in the intensity radiated from an atomic sample provides the relevant, atomic-level information. The analysis we present is very general and can be applied to a wide variety of atomic and molecular systems.

A generalized Jaynes-Cummings model with continuous external pumping is considered. The numerical results for the dynamics of the atom and the field mode are given. A comparison is made between the results for the case of continuous pumping with the results for the standard Jaynes-Cummings model where the field is put in as the initial condition. The results with the external field detuned from the cavity field are also given.