Optical surface waveguides have been fabricated by diffusing selenium into single-crystal CdS substrates to produce graded-composition CdSxSe1−x crystals. Planar guides which confine a beam in one dimension and guides produced by masked diffusion capable of two-dimensional beam confinement have been obtained. Evidence of guiding of light from a HeNe laser is provided by photographs and by measurements of spatial intensity profiles. Losses are estimated to be 10–15 dB/cm for one-dimensional guides and 30–40 dB/cm for two-dimensional guides.
Some examples of lidar backscatter and depolarization profiles obtained at the South Pole during the austral summer period 1976-77 are presented. The examples illustrate the variety of data obtainable from various meteorological conditions as well as how this kind of lidar can help determine cloud layer structures in the polar atmosphere. Clear sky ice crystal precipitation and light ice precipitation under overcast sky conditions produced volume backscatter coefficients in the 2-4 x 10(-3)-km(-1) range and depolarization values up to 0.46, while mixed phase and supercooled water drop layers were also observed with maximum backscatter coefficients ranging from 5 x 10(-2) to 2.4 x 10(-1) km(-1) and depolarization values from a few to ~20%. Some of these layers may have contained aligned plates which resulted in enhanced backscatter values and lower depolarization values, therefore, the identification is sometimes ambiguous.
The fluorescence of Cds"se& "mixed crystals with band-gap gradients as large as 1200 eV/cm has been investigated at 77 K. The graded samples were produced by heating CdSe or CdS"Se& " platelets in a sulfur-selenium atmosphere. Some of the diffused crystals were post-treated in a cadmium atmosphere. Removal of surface material shifted the fluorescence spectra of the diffused crystals to longer wavelengths. The spectral position of fluorescence peaks was determined as a function of the thickness of the removed surface layer. Composition profiles were deduced from these data by correlating fluorescence wavelength with crystal composition. Error-function curves gave a good fit to experimentally determined profiles. Diffusion constants of 7. 0 x10 t3 and 1.6 x 10 tt cm2/sec were determined for diffusion temperatures of 600 and 650'C, respectively.
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