Propagation of light in an optically inhomogeneous medium near the critical point

George L. Lamb

George L. Lamb

Anita N. Wolff, John Ross, Robert H. Harding

We measure relaxation rates near the critical point and the left hysteresis limit of an optically bistable system, a ZnSe interference filter. Our ZnSe system has an inhomogeneous geometry where a long, narrow illuminated region has boundaries at a temperature near and below that of the lower state. We determine the critical angle, the angle of incidence of light at which the hysteresis limits coalesce to form a critical point, and perturb the system by changing the input power beyond the critical point. For incidence angles equal to or slightly greater than the critical angle, we find that relaxation rates increase exponentially as the critical point is approached. The critical exponents for perturbations which increase the input power beyond the critical point are greater than those for perturbations which decrease the input power. In either case, the critical exponents increase as the angle of incidence approaches the critical angle. When the hysteresis region is large, we find slowing down near the left hysteresis limit in accordance with our calculations based on a one-dimensional inhomogeneous model.

Samina Masood, Iram Saleem

Prabhat Kumar, Derek Kuldinow, Andres M. Castillo +2 more

Propagation of a light beam through a collisional and inhomogeneous beam of neutral particles is investigated. The light beam can be manipulated through the refractive index that is affected by the gaseous medium. Simultaneously, neutral particles experience optical dipole force and scattering force due to atomic polarizability, leading to particle trapping. The simulation results of fully coupled light-particle propagation show agreement with experimental data from the literature. The effects of particle density, detuning frequency with respect to the resonance frequency, and light intensity on the mutual guiding of light and particle beams is studied for particle beam densities below the critical density that results in single-mode operation of optical waveguides.

Sergei G. Krivoshlykov, I N Sisakyan

Methods of integrals of motion, coherent states, dynamical symmetry group, and density matrix formalism are used to describe the propagation of light in weakly inhomogeneous media, in particular, in a two-dimensional medium having a quadratic transverse distribution of the refractive index and an arbitrarily inhomogeneous longitudinal distribution. Expressions are obtained for the trajectories and widths of the modes and rays. The coefficients of coupling between the modes and rays due to the longitudinal inhomogeneity of the medium and distortion of the axis are discussed. It is shown that, for certain laws of longitudinal inhomogeneity, matching occurs when no energy redistribution takes place between the modes and mismatch is found when all the energy is coupled out of the medium. On the basis of these effects, methods of matched joining of two different graded-index optical waveguides and of coupling light out of a graded-index waveguide are proposed. It is shown that each initial mode of the medium is strongly coupled to three final modes. These results may be used in fiber-optic communication lines.