Space radiation damage in ZnO induced by subthreshold electrons: defect identity and optical degradation.

Space radiation damage in ZnO induced by subthreshold electrons was studied through reflectance spectra, electron paramagnetic resonance, and photoluminescence. Owing to the vacuum freezing treatment, perturbed singly ionized zinc vacancies (V'(Zn)⁻), chemisorbed species, and electrons in the conduction band and/or bound to shallow donor levels were observed. V'(Zn)⁻ is due to the ionization and the ionization-induced diffusion processes and is most likely responsible for the 420-nm absorption band. These results also support that the green luminescence in ZnO is related to zinc vacancies.

Trichroic prism assembly for separating and recombining colors in a compact projection display.

A trichroic prism assembly design, believed to be new, is proposed and demonstrated. This new design has the advantages of low s- and p-polarization dependence in the reflectance spectra of the optical coatings. Hence it can be used for both color separation and color recombination with polarization change. This new trichroic prism assembly is especially useful in a compact color projector employing reflective liquid-crystal light valves.

Low-voltage thin-film electroluminescent devices with low-resistivity stacked insulators.

The characteristics and mechanism of low-voltage-driven thin-film electroluminescent (TFEL) devices with low-resistivity (10(6)-10(7)-ohms cm) SiO(2)/Ta(2)O(5) and Al(2)O(3)/Ta(2)O(5) stacked insulating films have been studied. At 50-Hz sinusoidal wave voltage excitation, the threshold voltage of devices with a ZnS:Mn emitting layer is below 40 V, and the brightness and luminous efficiency are above 1000 cd/m(2) and 4 lm/W, respectively, with 60 V voltage. The characteristics of brightness versus voltage (B-V) curves, integrated charge versus voltage (Q-V) figures, and luminous efficiency versus voltage (eta-V) characteristics are different from conventional devices. The study of a special semiconductor layer--a thin probe-doped layer located at a different part of the pure ZnS layer--has proved that the excitation efficiency is not homogeneous across the emitting layer in this kind of device, and its value decreases from the anode toward the cathode, which is opposite of that made with TFEL devices with high-resistivity insulators. By offering a model of space-charge-limited current, the mechanism of low-voltage-driven thin-film electroluminescence, its optoelectronic characteristics, and the distribution characteristics of excitation efficiency across the emitting layer can be thoroughly explained.

Estimation of optical constants of thin film by the use of artificial neural networks.

A system for analyzing single-layer optical thin films has been formulated by the use of artificial neural networks. The training data sets stem from the computational results of the physical model of thin films, and they are used to train the artificial neural network, which, when done, can give values of film parameters in the millisecond time regime. The fast backpropagation algorithm is employed during training. The results of training are also given.

Infrared optical absorption loss of antireflection coatings on germanium and potassium chloride substrates at the 10-µm wavelength by the photothermal deflection technique.

The photothermal deflection technique is used to study the infrared absorption of antireflection coatings on Ge and KCl substrates. The thin films deposited by the thermal resistance evaporation technique, both with and without ion-assisted deposition, are investigated. The experimental results show that Ar-ion bombardment with low energy can evidently reduce the absorption of the coatings.

Properties of dielectric coatings produced by ion assisted deposition.

Some metal oxides, fluorides, and ZnS films deposited by ion assisted deposition are investigated as a function of ion energy, ion variety, and ion source type. Both optical and mechanical properties, such as optical stability, absorption and scattering losses, laser damage threshold, and durability, are examined for samples deposited with the assistance of four kinds of ion source and various preparation conditions.