Surface motion induced by the interaction of pulsed laser radiation with highly absorbing dielectric fluids (original) (raw)
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Excitation of Capillary Waves in Strongly Absorbing Liquids by a Modulated Laser Beam
Applied Optics, 1999
Several mechanisms for the excitation of capillary waves and for the development of the average deformation of a liquid surface under the action of a modulated laser beam are considered. The amplitude of the capillary wave in a strongly absorbing solution of the dye LDS 751 in ethylene glycol is experimentally studied as a function of laser intensity. Consecutive changes in the predominant mechanism of the excitation with increasing laser intensity are observed and described. At low laser intensities the mechanism connected with the creation of a surface tension gradient prevails. This mechanism becomes nonlinear with increasing influence of the convective motion. In addition, pressure pulsations of the convective flow start to contribute significantly to the generation process. The resonances of capillary waves in a cylindrical container are also investigated and used for determining the surface tension and viscosity of the liquid.
Journal De Physique, 1982
2014 La surface libre d'un échantillon liquide (huile lourde) est chauffée au moyen d'un faisceau laser Gaussien. On présente des enregistrements photographiques de la forme de la surface et de la distribution des vitesses. La surface passe par une étape initiale de dilatation, suivie de la formation d'une dépression. Une interprétation théorique en est donnée dans le cadre de solutions stationnaires de l'équation de Navier-Stokes, considérant la dépendance de la masse volumique et de la tension superficielle vis-à-vis de la température. On prouve que le signe des variations de la hauteur de la surface dans la région chaude dépend de façon critique des paramètres expérimentaux. Les expériences et les résultats théoriques montrent que le phénomène est dû à la compétition entre les variations de la masse volumique et de la tension superficielle. Abstract. 2014 The free-surface of a liquid sample (heavy oil) is locally heated by irradiation with a Gaussian laser beam. Photographic records of the surface profile and flow pattern are presented. The free-surface passes by an earlier dilatation stage, followed by the formation of a pit in the top of the expanded region. A theoretical analysis based on the stationary solution of Navier-Stokes equation with temperature-dependent density and surfacetension is made. It is shown that the sign of the surface-height variations in the hot region depends critically on the values of the dimensionless quantities characterizing the experiment. The surface profile and the velocity distribution are calculated and compared with the experimental results. We conclude that the phenomena observed are due to competition between the density-and surface-tension gradients.
Quantitative assessment of radiation force effect at the dielectric air-liquid interface OPEN
We induce nanometer-scale surface deformation by exploiting momentum conservation of the interaction between laser light and dielectric liquids. The effect of radiation force at the air-liquid interface is quantitatively assessed for fluids with different density, viscosity and surface tension. The imparted pressure on the liquids by continuous or pulsed laser light excitation is fully described by the Helmholtz electromagnetic force density. The correct form of the momentum of light within dielectric materials and the effects caused by the radiation forces when light passes through adjacent media have been extensively debated for over a century 1–9. Although the radiation pressure effects were predicted in 1871 10 , and experimentally observed in 1900 11 , a dilemma was created by controversial interpretations of the theories proposed by Minkowski in 1908 12 and Abraham in 1909 13 to explain the energy-momentum tensor of light. The history of the Abraham-Minkowski dilemma is intimately linked to the difficulties in sensing and interpreting the effects produced by radiation forces, which led to erroneous interpretations favoring one of the theories. This is based on the fact that both momentum descriptions have simple forms when light is incident from free space on a transparent and non-dispersive dielectric medium; Minkowski predicts a momentum in the medium proportional to its refractive index (n) and the photon momentum in the vacuum () p 0 as = p np M 0 , while Abraham predictions is in the form = / p p n A 0. = / p U c 0 , U is the energy of light and c is the speed of light. The Minkowski-Abraham controversy has theoretically been resolved by the correct division of momentum between field and medium 1. Early experimental investigations pursued answers to the dilemma, and continued to shed light on to this controversy. A number of reviews discuss these early experiments in details 1–9 , although the conclusions derived favor either theory. For instance, Jones and coauthors 14 showed that a mirror submerged in a medium experiences a force consistent with each photon having the Minkowski momentum. Ashkin and Dziedzic 15 demonstrated that focused laser pulses created deformations of the water-air interface; the surface of the liquid experienced a net force outward from the water as predicted by Minkowski. Although, it was later assessed that the bulging of the liquid was also influenced by radial electrostriction forces 8,16. Walker and coauthors 17 measured the torque exerted on a disk suspended on a torsion pendulum. The experiments provide evidence in favor of the Abraham form. Zhang and coauthors 18 performed experiments based on Ashkin and Dziedzic 15 scheme. They show the interplay between Minkowski and Abraham forces illuminating water or mineral oil. On initial inspection, experimental results may appear to be in favor of one of the formulations. However, detailed analysis demonstrates explicitly and directly the equivalence of a number of different energy momentum tensors, provided the accompanying material tensor is taken into account 1,6. Yet there has been so far only limited qualitative experimental tests of our understanding of radiative transfer between electromagnetic radiation and dielectric media. Quantitative measurements of the effects of radiation forces on dielectric media have attracted large interest with the advent of optical manipulation of micro-particles in fluid media and its potential application in biological systems. Recently, Astrath and coauthors 19 measured surface deformation at the interface air-water generated by continuous and pulsed laser excitations using the photomechanical mirror (PM) method. The displacement caused by radiation forces was quantitatively described by the theory using the Helmholtz force density. The former
Nonlinear Laser-Induced Deformations of Fluid-Fluid Interfaces
2008
Experimentally, it turns out that radiation forces from a cw-laser on a liquid-liquid interface are able to produce giant deformations (up to about 100 µm), if the system is close to the critical point where the surface tension becomes small. We present a new model for such a fingerlike deformation, implying that the system is described as an optical fiber. One reason for introducing such a model is that the refractive index difference in modern experiments, such as those of the Bordeaux group, is small, of the same order as in practical fibers in optics. It is natural therefore, to adopt the hybrid HE 11 mode, known from fiber theory, as the fundamental mode for the liquid system. We show how the balance between hydrodynamical and radiation forces leads to a stable equilibrium point for the liquid column. Also, we calculate the narrowing of the column radius as the depth increases. Comparison with experimental results of the Bordeaux group yields quite satisfactory agreement as regards the column width.
Dynamics of shock waves generated in liquids by high-energy KrF laser
2008
The paper is devoted to R&D of novel experimental technique -laser-driven shock tube (LST) for modeling of Rayleigh-Taylor (R-T) and Richtmyer-Meshkov (R-M) hydrodynamic instabilities development at the contact surface of two immiscible liquids under a shock wave (SW) passage. 100-J, 100-ns KrF laser facility GARPUN has been used to irradiate some opaque liquids. A homogenizing focusing system combined multi-element prism raster and a lens to provide non-uniformity less then few percents across a square 7*7-mm spot, laser intensities being varied in the range of q = 0.004 -2 GW/cm 2 . Surface plasma blow off produced a planar SW propagated into the liquid. SW amplitudes as high as 0.8 GPa weakly damping with increasing thickness were measured in dibutyl-phthalate (DBP), which strongly absorbed UV laser light. Test bench experiments were performed to produce standing acoustic waves as initial perturbations at the interface between two immiscible liquids.
Theoretical considerations of laser-induced liquid–liquid interface deformation
Physica Scripta, 2013
In the increasingly active field of optofluidics, a series of experiments involving near-critical two-fluid interfaces have shown a number of interesting nonlinear effects. We here offer, for the first time to our knowledge, an explanation for one such feature, observed in experiments by Casner and Delville (2003 Phys. Rev. Lett. 90 144503), namely the sudden formation of 'shoulder'-like shapes in a laser-induced deformation of the liquid-liquid interface at high laser power. Two candidate explanations are the following. Firstly, the shape can be explained by balancing forces of buoyancy, laser pull and surface tension only, and the observed change of deformation shape is the sudden jump from one solution of the strongly nonlinear governing differential equation to another. Secondly, it might be that the non-trivial shape observed could be the result of temperature gradients due to local absorptive heating of the liquid. We report that a systematic search for solutions of the governing equation in the first case yields no trace of solutions containing such features. By contrast, an investigation of the second option shows that the narrow shape of the tip of the deformation can be explained by a slight heating of the liquids. The local heating amounts to a few kelvins, with the parameters given, although there are uncertainties here. Our investigations suggest that local temperature variations are the crucial elements behind the instability and the shoulder-like deformation.
Dynamics of shock waves generated in liquids by high-energy KrF laser
2008
The paper is devoted to R&D of novel experimental technique -laser-driven shock tube (LST) for modeling of Rayleigh-Taylor (R-T) and Richtmyer-Meshkov (R-M) hydrodynamic instabilities development at the contact surface of two immiscible liquids under a shock wave (SW) passage. 100-J, 100-ns KrF laser facility GARPUN has been used to irradiate some opaque liquids. A homogenizing focusing system combined multi-element prism raster and a lens to provide non-uniformity less then few percents across a square 7*7-mm spot, laser intensities being varied in the range of q = 0.004 -2 GW/cm 2 . Surface plasma blow off produced a planar SW propagated into the liquid. SW amplitudes as high as 0.8 GPa weakly damping with increasing thickness were measured in dibutyl-phthalate (DBP), which strongly absorbed UV laser light. Test bench experiments were performed to produce standing acoustic waves as initial perturbations at the interface between two immiscible liquids.