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Using light scattering and the photoelastic effect, we have investigated the frequency spectrum of giant acoustic shear wave packets generated in semiconducting CdS by high electric fields. The frequencies were in the range 100 to 1500 MHz, at least an order of magnitude lower than the predicted frequency for maximum net gain. The strains were high enough to cause permanent crystal damage.

Luminescence studies of thick (≥5 μm) GaAs epitaxial layers grown on Si substrates reveal regions of nonuniform stress associated with the presence of microcracks. Using cathodoluminescence spectroscopy as a tool for microcharacterization, the magnitude of the stress, derived from the peak positions of the luminescence spectra, is shown to increase gradually as a function of distance from the intersection of two microcracks. The greatest degree of stress relief was found at this intersection.

Pump-excited-state-absorption (ESA) measurements on Er3+-doped phosphates, fluorophosphates, and silicate bulk glasses indicate that ESA cross sections are approximately equal to ground state absorption (GSA) cross sections in the 800-nm band. The oscillator strengths of the ESA and GSA bands are also approximately equal, in qualitative agreement with Judd-Ofelt calculations. Fluorozirconate samples were found to have substantial populations in the upper excited states for the measurement conditions used and ESA transitions originating from four excited states were identified. Fluorozirconate fiber amplifiers and lasers at 1.55 μm, therefore, would have decreased efficiency for 800-nm pumping.