Experimental and theoretical studies of the recently patented prism light guide are described [L. A. Whitehead, U.S. Patent 4,260,220 (7 Apr. 1981)]. This device combines the total internal reflection of optical fibers with the low attenuation of air transmission of light. Since it can be moulded from acrylic plastic, the cost of the guide is low enough to make large-scale interior illumination with piped light feasible.

The enhancement of the scattered signal due to the mixing of two optical beams in a plasma is observed. The two beams are produced in a dual-cavity organic-dye laser pumped by a Q-switched ruby laser. The presence of enhanced oscillations is demonstrated by a 50% increase in the intensity of the satellite in the scattered light spectrum of a third beam.

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Enhanced electron-density fluctuations in a plasma jet are produced by the nonlinear interaction of the plasma with two pulsed dye-laser beams, one of which is of variable frequency. The properties of the enhanced fluctuations are studied as a function of the laser intensities and frequencies by observing the spectra of ruby-laser radiation scattered by the density fluctuations. The ruby laser also pumps the dye lasers. The dependence of the scattered signals on the laser intensities is well described by theory, but the response of the plasma to mixing forces of variable frequency is anomalous.

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