The electrical characteristics of ZnS:Mn alternating-current thin-film electroluminescent (ACTFFL) devices grown by atomic layer epitaxy are assessed as a function of the thickness of the phosphor layer using capacitance-voltage (C-V) and internal charge-phosphor field (Q-F,) analysis. Deviations from the ideal in the measured CW and Q-F, characteristics are ascribed to the generation of space charge in the phosphor layer during ACTFEL device operation. C-V overshoot deviations are correlated to space charge generation via a simulation employing a single sheet of charge model which assumes that the centroid of the generated space charge is located at a discrete sheet within the phosphor. Space charge generation in these atomic layer epitaxy (ALE) ZnS:Mn ACTFEL devices is ascribed to impact ionization of the zinc vacancy portion of chlorine-zinc vacancy self-activated defect complexes. A thermodynamic argument is provided which suggests that zinc vacancies are created via self-compensation of ZnS when the ZnS is unintentionally doped with chlorine. It is contended that space charge generation could even be desirable in ALE ZnS:Mn ACTFEL devices because it leads to better aging stability and improved performance. 0 1995 American Institute of Physics.

Circular optical waveguides have been fabricated from vacuum-deposited Ag layers by ion migration technique into soda-lime substrate glass. In this method two different guide patterns, one of which is the mirror image of the other, are made. Later the guide patterns are placed on top of each other and circular guides are thus obtained. The ends of the guides are studied by optical microscope and the near-field scanning method. The optical loss spectrum is measured from 450 to 1600 nm.

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Wavelength multiplexers and demultiplexers using a chirped grating and an ion-exchanged multimode waveguide are presented. The waveguide is prepared by the electric-field-assisted ion-exchange technique, and the chirped grating is fabricated by the computer-controlled electron-beam writing technique. The device requires no collimating and focusing components and has the advantages of (1) high resolution, (2) large channel number, (3) small cross talk, (4) low insertion loss, (5) low loss coupling to multimode fiber, (6) compact and stable rugged structure, and (7) possibility of economical mass production. The design considerations and the fabrication process are described, and the demultiplexing characteristics of the fabricated device are discussed.

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