Optical applications of laser-induced gratings in Eu doped glasses.

Laser-induced changes in the refractive index are used to create superimposed transient population gratings and permanent structural gratings in Eu(3+) doped silicate and phosphate glasses. Potential uses for these laser-induced gratings (LIGs) are investigated. First, the structural gratings are shown to be permanent at room temperature and their use as a holographic storage medium is discussed. Second, a permanent LIG of this type is used to demultiplex multifrequency laser beams, demonstrating its use as a tunable line filter. Third, the transient LIG is used to modulate the amplitude of a laser beam which is passed through the sample and scatters off the permanent LIG. This results in information being transferred from one beam to another beam. It was found that thermal lensing plays an important role in the formation of this type of permanent LIG and a procedure for determining the tilt angle of the fringes of the LIG is discussed.

Analysis of Low Temperature Viscosity Data for Three NBS Standard Glasses.

The low temperature viscosities of three glasses established as viscosity standards at the National Bureau of Standards are reported. The data overlap results which appear on the published certificates between 109 and 1012 poise and present extensive measurements up to 1016 poise. The measurements were made using both the fiber-elongation and beam-bending methods. No evidence of an Arrhenius behavior was found for any of the three glasses, even though the measurements covered a narrow range of temperatures. An analysis of the inherent measurement uncertainty associated with each method indicates that the fiber-elongation measurements are more precise than the beam-bending measurements. Analysis of the data and its uncertainty by the Fulcher Equation supports the conclusions of the error analysis.