Measurement of the decay of light-induced gratings for characterization of QW heterostructures of type I and II

Using a non-resonant transient grating technique the mobility and recombination lifetime of free carriers in type I and type II QW heterostructures is measured. For the lattice-matched type II Ca_xSr_1−xF₂/GaAs structures the diffusion coefficient as well as the diffraction efficiency is found to be affected by carrier separation into different layers. For GaAs/GaAlAs superlattices a strong influence of the barrier parameters on the inplane diffusion of heavy holes is observed.     

Ein Struktursatz für idempotente Halbkörper

Ohne ZusammenfassungVorgelegt vonL. Rédei     

Zur Theorie Levitzkischer Radikale in Halbringen

Ohne Zusammenfassung     

Über Halbringe und Halbkörper. II

Ohne Zusammenfassung Vorgelegt von L. Rédei     

Über Halbringe und Halbkörper. III

Ohne Zusammenfassung Vorgelegt von L. Rédei     

Phytosanitary irradiation of fresh tropical commodities in Hawaii: Generic treatments,commercial adoption,and current issues

Hawaii is a pioneer in the use of phytosanitary irradiation. The commercial X-ray irradiation facility, Hawaii Pride LLC, has been shipping papaya and other tropical fruits and vegetables to the United States mainland using irradiation for 11 years. Irradiation is an approved treatment to control quarantine pests in 17 fruits and 7 vegetables for export from Hawaii to the US mainland. Hawaiian purple sweet potato is the highest volume product with annual exports of more than 12 million lbs (5500 t). The advent of generic radiation treatments for tephritid fruit flies (150 Gy) and other insects (400 Gy) will accelerate commodity export approvals and facilitate worldwide adoption. Lowering doses for specific pests and commodities can lower treatment costs and increase capacity owing to shorter treatment times, and will minimize any quality problems. Current impediments to wider adoption include the 1 kGy limit for fresh horticultural products, the labeling requirement, and non-acceptance of phytosanitary irradiation in Japan, the European Union, and elsewhere. Irradiation has potential as a treatment for unregulated imports to prevent new pest incursions.     

Gigahertz modulators using bulk acousto-optic interactions in thin-film waveguides

Abstract

When bulk acoustic waves are applied to an optical waveguide, several modulation effects are observed, depending on the type of wave (longitudinal or shear). Longitudinal sound waves frequency-shift the guided light, thus providing a means of modulating light in a wide variety of waveguide materials. Using thin-film mosaic acoustic transducer technology, we have demonstrated such modulation at frequencies in the gigahertz region. By segmenting the acoustic transducer electrodes, the same arrangement can be used for deflecting the light since, with this arrangement, the acoustic field sets up a time-varying grating whose spatial frequency is set by the segment spacing. Theoretical frequency limitations on these devices do not appear to be important until approximately 30 GHz is reached. Thus, they are potentially useful for extremely wide-band data links. Experiments at 1.5 GHz show 30% bandwidth of acoustic modulation using optical heterodyne detection.