Radiation forces on a dielectric sphere in the Rayleigh scattering regime

Holography, coherent light amplification and optical phase conjugation with photorefractive materials

The light-matter interaction has been at the heart of major advances from the atomic scale right to the microscopic scale over the past four decades. Confinement by light, embodied by the area of optical trapping, has had a major influence across all of the natural sciences. However, an emergent and powerful topic within this field that has steadily merged but not gained much recognition is optical binding: the importance of exploring the optically mediated interaction between assembled objects that can cause attractive and repulsive forces and dramatically influence the way they assemble and organize themselves. This offers routes for colloidal self-assembly, crystallization, and organization of templates for biological and colloidal sciences. In this Colloquium, this emergent area is reviewed looking at the pioneering experiments in the field and the various theoretical approaches that aim to describe this behavior. The latest experimental studies in the field are reviewed and theoretical approaches are now beginning to converge to describe the binding behavior seen. Recent links between optical binding and nonlinearity are explored as well as future themes and challenges.

/pdf/colloquium-gripped-by-light-optical-binding-2zatv4aui8.pdf

Colloquium: Gripped by light: Optical binding

Calculations of the nonlinear-optical behavior are developed for model composites of nanospheres with a metallic core and nonlinear shell or with a nonlinear core and metallic shell suspended in a nonlinear medium. Optical phase conjugation is shown to be enhanced from each nonlinear region because the optical field can be concentrated in both the interior and the exterior neighborhoods of the particle and magnified at the surface-mediated plasmon resonance. For the model composite with a metallic core, a limited range of resonance tunability can be achieved by adjustment of shell thickness; the frequency range is dependent on the dielectric dispersion of the metal. For the composite with a metallic shell instead of a metallic core, this restriction is reduced so that tunability from ultraviolet to infrared can be attained. Enhancement of the phase-conjugate signal is calculated for the electrostrictive mechanism dominant in the microsecond time scale and for the electronic mechanism dominant in the picosecond time scale. Calculations based on the dielectric functions for gold and for aluminum indicate that phase-conjugate reflectivity enhancements of 108 can be achieved. The imaginary components of the composite dielectric functions are shown to limit the magnitude of the field enhancement at the surface-plasmon resonance and determine the absorption and figure of merit of the composite.

Composite structures for the enhancement of nonlinear-optical susceptibility

In this paper we report degenerate four-wave-mixing measurements of the nonlinear coefficient of rutile and a number of optical glasses at 1.06 μm. We define a figure of merit which measures the suitability of a material for nonlinear waveguide switches and show that the best glasses have figures of merit substantially higher than any other material. We include a brief discussion of the types of switching elements that could be made with these materials.

Nonlinear optical glasses for ultrafast optical switches

A Fabry-Perot resonator containing an electrooptic element driven by the transmitted light can be used for a number of light processing operations. We describe the use of such devices for pulse Shaping, optical limiter, and optical logic applications. "Optical triode" operation is demonstrated. We also propose and demonstrate a new type of "high-nonlinearity" operation which permits multilevel optical logic and switching operations.

Electrooptic nonlinear Fabry-Perot devices

We present the derivation of scaling relationships that describe the behavior of liquid suspensions of dielectric spheres as nonlinear optical media and report results of four-wave mixing experiments that are in good agreement with these predictions.

Use of a liquid suspension of dielectric spheres as an artificial Kerr medium

Under suitable conditions, the boundary between a linear and a nonlinear (Kerr effect) medium should have a reflection coefficient which exhibits hysteresis as a function of optical intensity. We present the first experimental evidence of this effect. Experiments were performed using ∼1‐ns ruby laser pulses incident on a glass‐CS2 boundary.

Optical bistability at a nonlinear interface

We describe the results of a detailed experimental study of the reflectivity of a nonlinear interface under the influence of intense ruby laser pulses incident in a Gaussian beam at grazing angles. The nonlinear interface was the interface between a linear optical material (glass) and a nonlinear material with a positive optical Kerr coefficient (CS 2 ). Optical hysteresis was observed as a function of incident light intensity. The nonlinear reflectivity showed behavior which differs from the predictions of previously published plane-wave calculations. We interpret our results with the aid of a numerical analysis of a two-dimensional Gaussian beam case.

Experimental studies of a nonlinear interface

The optical constants of evaporated MgF2 films were determined over the 1050–1600-A wavelength range from measured transmittance and near-normal incidence reflectance measurements. The complex refractive index was studied as a function of film deposition conditions and correlated with microstructural examinations by transmission electron microscopy. Absorption by the low energy tail of an exciton band and scattering from inhomogeneities were found to account for the film’s loss in this wavelength range. Both of these factors were determined largely by substrate temperature during the film deposition.

P. J. Maloney

Papers

Electrooptic nonlinear Fabry-Perot devices

Use of a liquid suspension of dielectric spheres as an artificial Kerr medium

Optical bistability at a nonlinear interface

Experimental studies of a nonlinear interface

Vacuum ultraviolet loss in magnesium fluoride films.