arXiv subjects

P. C. Chaumet

Publications and source records attributed to P. C. Chaumet.

4 recordsLinked to original sources

arXiv2003

Time averaged total force on a dipolar sphere in an electromagnetic field

We establish the time averaged total force on a subwavelength sized particle in a time harmonic varying field. Our analysis is not restrictive about the spatial dependence of the incident field. We discuss the addition of the radiative reaction term in the polarizability in order to correctly deal with the scattering force. As a consequence and illustration, we assess the degree of accuracy of several polarizability models previously established.

physics.optics↗

arXiv2003

Coupled Dipole Method Determination of the Electromagnetic Force on a Particle over a Flat Dielectric Substrate

We present a theory to compute the force due to light upon a particle on a dielectric plane by the Coupled Dipole Method (CDM). We show that, with this procedure, two equivalent ways of analysis are possible, both based on Maxwell's stress tensor. The interest in using this method is that the nature and size or shape of the object, can be arbitrary. Even more, the presence of a substrate can be incorporated. To validate our theory, we present an analytical expression of the force due to the light acting on a particle either in presence, or not, of a surface. The plane wave illuminating the sphere can be either propagating or evanescent. Both two and three dimensional calculations are studied.

physics.optics↗

arXiv2003

Electromagnetic force on a metallic particle in presence of a dielectric surface

By using a method, previously established to calculate electromagnetic fields, we compute the force of light upon a metallic particle. This procedure is based on both Maxwell's Stress Tensor and the Couple Dipole Method. With these tools, we study the force when the particle is over a flat dielectric surface. The multiple interaction of light between the particle and the surface is fully taken into account. The wave illuminating the particle is either evanescent or propagating depending an whether or not total internal reflection takes place. We analyze the behaviour of this force on either a small or a large particle in terms of the wavelength. A remarkable result obtained for evanescent field illumination, is that the force on a small silver particle can be either attractive or repulsive depending on the wavelength. This behaviour also varies as the particle becomes larger.

physics.optics↗

arXiv2003

Optical binding of particles with or without the presence of a flat dielectric surface

Optical fields can induce forces between microscopic objects, thus giving rise to new structures of matter. We study theoretically these optical forces between two spheres, either isolated in water, or in presence of a flat dielectric surface. We observe different behavior in the binding force between particles at large and at small distances (in comparison with the wavelength) from each other. This is due to the great contribution of evanescent waves at short distances. We analyze how the optical binding depends of the size of the particles, the material composing them, the wavelength and, above all, on the polarization of the incident beam. We also show that depending on the polarization, the force between small particles at small distances changes its sign. Finally, the presence of a substrate surface is analyzed showing that it only slightly changes the magnitudes of the forces, but not their qualitative nature, except when one employs total internal reflection, case in which the particles are induced to move together along the surface.

physics.optics↗