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Register a new userDripping, pressure and surface tension of self-trapped laser beams
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We show that a laser beam which propagates through an optical medium with Kerr (focusing) and higher order (defocusing) nonlinearities displays pressure and surface-tension properties yielding capillarity and dripping effects totally analogous to usual liquid droplets. The system is reinterpreted in terms of a thermodynamic grand potential, allowing for the computation of the pressure and surface tension beyond the usual hydrodynamical approach based on Madelung transformation and the analogy with the Euler equation. We then show both analytically and numerically that the stationary soliton states of such a light system satisfy the Young-Laplace equation, and that the dynamical evolution through a capillary is described by the same law that governs the growth of droplets in an ordinary liquid system.
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In this paper we report on 2D numerical simulations concerning linear and nonlinear evolution of surface-tension-driven instability in two-fluid systems heated from below using classical and phase-field models. In the phase-field formalism, one introduces an order parameter called phase-field function to characterize thermodynamically the phases. All the system parameters are assumed to vary continuously from one fluid bulk to another (as linear functions of the phase-field). The Navier-Stokes equation (with some extra terms) and the heat equation are written only once for the whole system. The evolution of the phase-field is described by the Cahn-Hilliard equation. In the sharp-interface limit the results found by the phase-field formalism recover the results given by the classical formulation.
We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously induced by the presence of pump depletion in the cavity, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.
Shallow water wave phenomena find their analogue in optics through a nonlocal nonlinear Schrodinger (NLS) model in $(2+1)$-dimensions. We identify an analogue of surface tension in optics, namely a single parameter depending on the degree of nonlocality, which changes the sign of dispersion, much like surface tension does in the shallow water wave problem. Using multiscale expansions, we reduce the NLS model to a Kadomtsev-Petviashvilli (KP) equation, which is of the KPII (KPI) type, for strong (weak) nonlocality.
We analyze the existence and stability of two kinds of self-trapped spatially localized gap modes, gap solitons and truncated nonlinear Bloch waves, in one-and two-dimensional optical or matter-wave media with self-focusing nonlinearity, supported by a combination of linear and nonlinear periodic lattice potentials. The former is found to be stable once placed inside a single well of the nonlinear lattice, it is unstable otherwise. Contrary to the case with constant self-focusing nonlinearity, where the latter solution is always unstable, here, we demonstrate that it nevertheless can be stabilized by the nonlinear lattice since the model under consideration combines the unique properties of both the linear and nonlinear lattices. The practical possibilities for experimental realization of the predicted solutions are also discussed.
The physics related to the form factors of the energy momentum tensor spans a wide spectrum of problems, and includes gravitational physics, hard exclusive reactions, hadronic decays of heavy quarkonia, and the physics of exotic hadrons described as hadroquarkonia. It also provides access to the last global unknown property: the D-term. We review the physics associated with the form factors of the energy-momentum tensor and the D-term, their interpretations in terms of mechanical properties, their applications, and the current experimental status.
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