Generation of quadrature-squeezed light of ultrashort pulses in a medium with inertial cubic nonlinearity

A consistent quantum theory of self-action and cross-interaction of coherent light pulses in a cubically nonlinear medium is developed by using the momentum operator of the field, which takes into account the inertial nonlinearity. Specific features of generation of the quadrature-squeezed states of light pulses are considered. The spectrum of fluctuations of a quadrature below the shot-noise level is analyzed as a function of the relaxation time of nonlinearity and the magnitude of nonlinear phase additions, related to the self-action and cross-interaction.     

Squeezed states of light as self-similar structures

A new approach to investigating a broad class of dynamic states for a quantum oscillator is suggested. It is based on an invariant transformation of the equation to a new time determined by the quantum dispersion of the corresponding state. The squeezed states of a quantum system generated by the ground-state wave function are constructed. In coordinate representation, these states are described by a self-similar wave function localized near a classical trajectory. The statistics of the squeezed state of light is analyzed in the single-mode approximation. The parametric excitation of squeezed states for a quantum harmonic oscillator is considered.     

Filamentation of ultrashort light pulses in a liquid scattering medium

We have studied filamentation of 1-ps laser pulses in a scattering medium (aqueous suspension of 2-μm polystyrene microspheres) and compared filamentation dynamics to that in pure water. Our results indicate that light scattering does not alter filamentation dynamics in general, but rather results in farther position of the nonlinear focus, shorter filament length, and the development of speckle structure in the peripheral part of the beam. The experimental observations are qualitatively reproduced by the numerical model which accounts for diffraction, self-focusing, multiphoton absorption, and light scattering introduced through a stochastic diffusion and diffraction term.     

Generation of phase-correlated light pulses in a hyper-Raman active medium

We analysis within the quantum setting the effect of correlation of monochromatic fields of the Stokes and parametric radiation generated in a two-photon-absorbing medium by hyper-Raman scattering and four-wave mixing, respectively. Our results show that when there is destructive interference between the two processes, both modes are amplified in the medium in a correlated way, so that beyond a certain characteristic distance they propagate in a stationary manner with the same amplitudes and photon statistics but with opposite phases, while the medium becomes transparent to them. We calculate the intensity of the fields, the emission linewidths, and the diffusion of the total phase, the latter determining the extent of phase noise correlation at the output. We also show that no matter how the phases of the separate modes diffuse, the quantum fluctuations in the total phase may be completely squeezed. Zh. éksp. Teor. Fiz. 111, 1942–1954 (June 1997)     

Soliton-like propagation of light pulses in a nonlinear photonic crystal

On the basis of computer simulation, we analyze the dynamics of interaction of subpulses localized inside certain layers of a one-dimensional nonlinear photonic crystal. Localized subpulses are shown to move and interact like solitons. Possible scenarios of their interaction are described: a spatially periodic regime, the merging of several subpulses with similar characteristics into a single higher intensity and more slowly propagating subpulse, and the formation of an immovable pulse in a layer of the photonic crystal. To verify the results of the computer simulation and to elucidate the nature of spatially localized structures forming, a comparison with the analytical solution for a medium with cubic nonlinearity is performed.     

Cone-type light beam structure in a nonlinear medium

The formation is predicted of a cone-type structure in an intense light beam propagating in an amplifying medium exhibiting the Kerr nonlinearity and a multiphoton absorption.     

Collisions of unipolar subcycle pulses in a nonlinear resonantly absorbing medium

Collisions of unipolar subcycle pulses in a nonlinear resonant medium that coherently interact with it are studied theoretically. The dynamics of spatial polarization structures and population difference that the pulses induce in the medium are analyzed. A surprising feature is that the medium is capable of “remembering” the result of the interaction with the pulses and their collisions during times comparable to the polarization relaxation time. An analysis of the dynamics of light-induced structures makes it possible to judge the parameters of subcycle pulses at the times longer than the pulse duration, which, in the future, can be useful in their detection.     

Three-component superposition states of light in a dissipative medium

The process of the simultaneous absorption of three photons in a medium possessing weak one-photon absorption is analyzed. The mode experiencing absorption is perturbed externally via a three-photon parametric process. It is shown that a steady-state, three-component superposition state of light can exist in this system in the range where the amplitude of the state is small (small perturbations of the system). The latter condition is due to the fact that, in this range of interactions, the field spends significantly more time in one of three types of superposition states of light that form an ensemble of quantum trajectories of the system than in the other two.     

Self-recovery of wavefront in a nonlinear light scattering medium

Both theoretical and experimental studies of wavefront self-recovery of intense light beam propagating through heterogeneous nonlinear scattering medium are described. The self-recovery of the light beam wavefront is shown to be observed in the definite range of the light intensities when a mismatch of the linear refractive indices of the medium hetero components is compensated by nonlinear light-induced changes of refractive indices.     

Transmission of a light pulse by a nonlinear medium

Resonance interaction is considered for a pulse of monochromatic radiation in a medium of phthalocyanin type, on the basis of a two-level model. The change in pulse width and height are deduced, as is the degree of bleaching.