Modules that perform photorefractive two-beam coupling operations have been built, characterized, and tested. These portable modules, interconnected by fiber optics, dispense with the need for repeated alignment and greatly facilitate the prototyping of complex signal- or image-processing photorefractive circuits. To evaluate the performance of the modules in a photorefractive circuit, we interconnected them in the feature extractor configuration: a ring configuration composed of two modules that selects the strongest signal within the signals presented on its input. With two signals at the input, an output contrast ratio of 45.4 dB is obtained for an input contrast ratio of 5 dB.

We report the first experimental demonstration of cavity-induced resonances that occur without total internal reflection. We obtained these resonances by observing the fluorescence spectrum from the molecules enclosed within a small, lossy capillary of the type used for capillary zone electrophoresis. Even with weak reflections from the capillary inner walls, enough feedback exists to superimpose resonances on the otherwise smooth fluorescence spectrum. These resonances, commonly called morphology-dependent resonances or whispering-gallery modes, have typically been observed only in cavities in which total internal reflection is present.

We studied the angular distribution of fluorescence from a small, lossy capillary filled with a laser-dye solution. We found that the fluorescence is isotropic for the liquid core and that, far from the liquid-solid phase transition, this isotropy shows no temperature dependence. This result, an extension of studies with solid cylinders, is at variance with theoretical expectations for solids as well as with previous reports by other investigators but is explained by the motion of the molecules in the liquid. Therefore the optimal viewing angle for capillary zone electrophoresis experiments is near 90° because the elastic scattering of the incident laser light is at or near a minimum for these small capillaries. This reduces contamination of the fluorescence signal as a result of stray laser light in the optical system.

We examine four theories that predict the scattered radiation from a system composed of a small sphere and a plane and show that in the far field the scattering amplitude components predicted by these theories are essentially the same. We express the scattering intensities in Mueller matrix representation and examine the far-field Mueller matrix as a function of various parameters.

Two limiting expressions occur for scattering from very small spheres. One occurs when the refractive index becomes small (Rayleigh scattering), and the other occurs when the sphere becomes perfectly conducting (Thomson scattering). We explore the scatter from small spheres having real refractive indices. For such spheres, resonance conditions occur, and the resulting scattering coefficients are no longer proportional to the volume of a sphere.

A ray-tracing model was used to derive the light scattering Mueller matrix element curves for a dipole near a perfect surface as a function of incident angle, scattering angle, and surface refractive index. This system represents a fundamental system composed of a perfect plane surface and a perfect (Rayleigh) scatterer.

The light-scattering Mueller matrix for an r almost-equal-to 2.0-mu-m radius, rough quartz fiber contains phase information different from that of a perfectly cylindrical fiber of the same optical constants and radius. The rough surface creates higher-frequency, smaller-amplitude oscillations that mask the lower-frequency oscillations indicative of a perfect cylinder. Roughness also causes scatter outside the plane of incidence.

We discuss scattering in the context of the Stokes vectors and Mueller matrices that completely characterize the polarization state of the scattered light. A polar nephelometer is used to measure the light scattering Mueller matrix elements of various ideal systems. These systems are fundamental and solvable theoretically. The scattering systems can be perturbed and the amount of perturbation can be quantified. The light-scattering signals can then be examined as a function of the amount of perturbation. Eventually, the perturbation dominates the system so that the addition of more of the perturbation does not significantly alter the appearance of the scattering system or of the polarized light scattering signals. These saturated systems may also be thought of as fundamental systems. In this paper we examine some fundamental systems and discuss models which predict the polarization state of some highly perturbed scattering systems.

The light-scattering Mueller matrix is experimentally determined for a 0.26-mu-m-radius quartz fiber mounted on an aluminum surface at five different incident angles. The results are compared with those for the experimental scattering elements of the lone fiber and the lone surface and with theoretical results derived from a simple fiber-surface model. The experimental matrix elements of the fiber-surface system do not resemble the matrix elements from any of these other systems.

The light-scattering Mueller matrix for an r = 0.345-microm-radius quartz fiber, illuminated at lambda = 0.4416 microm, is examined as a function of contamination with MgO crystals. When the MgO contamination is low, the matrix elements resemble those of a fiber of slightly larger radius. The MgO contamination creates higher-frequency, smaller-amplitude oscillations in the matrix elements that mask the lower-frequency oscillations indicative of a perfect cylinder. The contamination also causes scatter outside the plane of incidence.

Fluorescent angular scattering from laser dye-filled small-core-diameter fibers shows increased backscattered fluorescent emissions as the core diameter decreases below 23 microm. The fluorescent angular scattering from Coumarin 7 laser dye-filled hollow-core quartz fibers were measured at three different fluorescent wavelengths and compared with the elastic scattered incident radiation at 442 nm.

We discuss scattering in the context of the Stokes vectors and Mueller matrices that characterize the interaction. In order to study surface structures using light-scattering techniques it is useful to examine the nature of light scattered from perfect and perturbed mirror surfaces.

We measured the Mueller elastic light-scattering matrix for two parallel dielectric (quartz) fibers over the angular range 5-170-degrees by using the polarization-modulation technique. These experimental results are the first verification to our knowledge of a recent theory for light scattering from parallel fibers. Measurements were made for both end-on and side-on illuminations at normal incidence for submicrometer-sized fibers at various separations from 2 to 66-mu-m. Electrostatic attraction between the fibers prevented the investigation for separations below 2-mu-m. The possibility of designing a sensitive vibration detector is suggested.

The entire sixteen-element light scattering matrix is experimentally determined for a circular cross-sectioned conducting fiber illuminated with lambda = 632.8-nm radiation at normal incidence. The radius (1.552 +/- 0.007) microm, determined by comparison to Mie theory modified for cylinders, indicates that micron-sized fiber radii can be determined within a few nanometers by polarized light scattering techniques. We discuss changes that occur in matrix elements as a quartz fiber is coated with aluminum to form a conducting fiber. Mueller matrices can be used to study time-varying processes, such as water vapor buildup on small particles and surfaces.

The coherent light inelastically scattered from an ideal fluorescent sphere illuminated by an electromagnetic wave is analyzed using an extension of Mie theory. Scattering coefficients are solved specifically for plane-wave illumination. The resulting inelastically scattered radiation is similar to that of elastically scattered radiation from a sphere. These results are illustrated by numerical calculations for several specific, but arbitrary, cases.

We used sub-microm-sized quartz fibers to probe a visible light, standing electromagnetic wave inside a laser ring cavity. By observing variations in the cavity's irradiance decay lifetime, we observed the longitudinal shape of the standing wave.

A highly motivated, systematic and fundamental approach to surface scattering requires that the initial surfaces be fundamental (perfect or ideal) and that the contamination to produce surface scattering be known and controlled. Rough surfaces are considered to be perturbed perfect surfaces that have reached their final condition through some continuum contamination process. This approach permits the classification of surfaces according to the light scattering response to the surface as it is perturbed away from its initial condition. All light scattering data are reported in the context of the Stokes vector and Mueller matrices. Some comparisons to ellipsometry and bi-directional reflection distribution functions (BRDF) are made.

The stretching and bending of polished and industrial-grade metallurgical surfaces changes the appearance of the specimen’s surface. The changes in surface structure can be detected in the polarized light scattered from the surface cracks and other defects, which act as scattering centers. In order to interpret light scattering signals from complex surfaces, we first examine the nature of light scattered from a perfect mirror surface, a degraded mirror, a line on a mirror, a randomly sanded surface, and, finally, the industrial grade metal surfaces damaged by stretching and bending.