Universal Long-Range Nanometric Bending of Water by Light (original) (raw)

Nanomechanical effects of light unveil photons momentum in medium

Scientific Reports, 2017

Precision measurement on momentum transfer between light and fluid interface has many implications including resolving the intriguing nature of photons momentum in a medium. For example, the existence of Abraham pressure of light under specific experimental configuration and the predictions of Chau-Amperian formalism of optical momentum for TE and TM polarizations remain untested. Here, we quantitatively and cleanly measure nanomehanical dynamics of water surface excited by radiation pressure of a laser beam. We systematically scanned wide range of experimental parameters including long exposure times, angle of incidence, spot size and laser polarization, and used two independent pump-probe techniques to validate a nano-bump on the water surface under all the tested conditions, in quantitative agreement with the Minkowski's momentum of light. With careful experiments, we demonstrate advantages and limitations of nanometer resolved optical probing techniques and narrow down actual manifestation of optical momentum in a medium.

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Optical Deformability of Fluid Interfaces

The formation, deformation, and break-up of liquid interfaces are ubiquitous phenomena in nature. In the present article we discuss the deformation of a liquid interface produced by optical radiation forces. Usually, the bending of such an interface by the radiation pressure of a c.w. laser beam is weak. However, the effect can be enhanced significantly if one works with a near-critical phase-separated liquid mixture, whereby the surface tension becomes weak. The bending may in this way become as large as several tenths of micrometers, even with the use of only moderate laser power. This near-criticality is a key element in our experimental investigations as reviewed in the article. The effect is achieved by working with a micellar phase of microemulsions, at room temperature. We give a brief survey of the theory of electromagnetic forces on continuous matter, and survey earlier experiments in this area, such as the Ashkin-Dziedzic optical radiation force experiment on a water/air surface (1973), the Zhang-Chang experiment on the laser-induced deformation of a micrometer-sized spherical water droplet (1988), and the experiment of Sakai et al. measuring surface tensions of interfaces in a non-contact manner (2001

Tailoring Optical Forces Behavior in Nano-optomechanical Devices Immersed in Fluid Media

Scientific reports, 2017

Emerging nano-optofluidic devices have allowed a synergetic relation between photonic integrated circuits and microfluidics, allowing manipulation and transport at the realm of nanoscale science. Simultaneously, optical gradient forces have allowed highly precise control of mechanical motion in nano-optomechanical devices. In this report, we show that the repulsive optical forces of the antisymmetric eigenmodes in an optomechanical device, based on a slot-waveguide structure, increases as the refraction index of the fluid medium increases. This effect provides a feasible way to tailor the repulsive optical forces when these nano-optomechanical devices are immersed in dielectric liquids. Furthermore, the total control of the attractive and repulsive optical forces inside liquids may be applied to design novel nanophotonic devices, containing both microfluidic and nanomechanical functionalities, which may find useful applications in several areas, such as biomedical sensors, manipulat...

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.

Light-induced deformation and instability of a liquid interface. I. Statics

Physical Review E, 2006

We study the dynamics of the deformation of a soft liquid-liquid interface by the optical radiation pressure of a focused cw gaussian laser beam. We measured the temporal evolution of both the hump height and the hump curvature by direct observation and by detecting the focusing effect of the hump acting as a lens. Extending the results of Yoshitake et al. [J. Appl. Phys. 97, 024901 (2005)] to the case of liquid-liquid interfaces and to the Bo 1 regime (Bo = (ω 0 / c ) 2 , where ω 0 is the beam waist and c the capillary length), we show that, in the Bo 1 and Bo 1

Asymmetric optical radiation pressure effects on liquid interfaces under intense illumination

Journal of the Optical Society of America B, 2003

Deformations of horizontal liquid interfaces by optical radiation pressure are generally expected to display similar behaviors whatever the direction of propagation of the exciting laser beam is. In the present experiment we find this expectation to be borne out, as long as the cw laser illumination is moderate in strength. However, as a striking contrast in the case of high field strengths, we find that either a large stable tether can be formed, or else that a break-up of the interface can occur, depending on whether the laser beam is upward or downward directed. Physically, the reason for this asymmetry can be traced to whether total reflection can occur or not. We also present two simple theoretical models, one based on geometrical optics, the other on wave optics, that are able to illustrate the essence of the effect. In the case leading to interface disruption our experimental results are compared with those obtained by Zhang and Chang for water droplets under intense laser pulses [Opt. Lett. 13, 916 (1988)]. A key point in our experimental investigations is to work with a near-critical liquid/liquid interface. The surface tension becomes therefore significantly reduced, which thus enhances the magnitude of the stationary deformations induced.

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.

Optohydrodynamics of soft fluid interfaces: Optical and viscous nonlinear effects

The European Physical Journal E, 2010

Recent experimental developments showed that the use of the radiation pressure, induced by a continuous laser wave, to control fluid-fluid interface deformations at the microscale, represents a very promising alternative to electric or magnetic actuation. In this article, we solve numerically the dynamics and steady state of the fluid interface under the effects of buoyancy, capillarity, optical radiation pressure and viscous stress. A precise quantitative validation is shown by comparison with experimental data. New results due to the nonlinear dependence of the optical pressure on the angle of incidence are presented, showing different morphologies of the deformed interface going from needle-like to finger-like shapes, depending on the refractive index contrast. In the transient regime, we show that the viscosity ratio influences the time taken for the deformation to reach steady state.

Universal Long-Range Nanometric Bending of Water by Light (original) (raw)

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