Lowest-order axial and ring mode lasing in confocal quasi-stadium laser diodes

We investigated the lasing modes of quasi-stadium laser diodes that have confocal cavity geometries, with stripe electrode contacts formed either along the cavity axis or a diamond-shaped trajectory. It was clearly demonstrated that by using narrow electrode contact patterns of 2 μm width, the lowest-order axial and ring modes were excited selectively. On the other hand, the second-lowest-order axial and ring modes were excited by using broad electrode patterns of 14 μm width. Experimentally obtained far-field patterns for lasers with broad and narrow electrode contact patterns agree very well with the simulation results obtained using an extended Fox-Li mode calculation method.     

Hydrogen effect on the optical and electrical properties of metal oxide and nitride thin films

Effect of hydrogen introduction into some metal oxide and nitride thin films was examined. Modification of electrical and optical properties by hydrogen introduction was examined on SnO₂${}_2$, Sn–GeO₂${}_2$, Ge–CdO₂${}_2$, ZnO. Electrical resistance could be reduced in some films without loosing their transparence to the visible light. Hydrogen introduction to Cu₃${}_3$N changed the film an electrical conductor. Films of AlN and TiN were rather insensitive to the hydrogen introduction; the hydrogen effect was only observed when the nitrides contain some imperfection in the compounds.     

Study of diethyl dithiophosphate adsorption on chalcopyrite and tennantite at varied pHs

The kinetics of diethyl dithiophosphate adsorption on chalcopyrite and tennantite has been studied by UV-visible spectroscopy at pH values of 4, 6, and 9. The concentration of diethyl dithiophosphate in the solution has been monitored as a function of time and pH for both minerals. It was found that the adsorption tendency of diethyl dithiophosphate on both minerals decreased with the increasing pH treatments. This is due to the existence of metal hydroxide species onto the mineral surface in more alkaline condition inhibiting the adsorption of diethyl dithiophosphate species. In comparison to that of chalcopyrite, tennantite possessed slightly higher adsorption of diethyl dithiophosphate in acid condition, while vice versa correlation observed at other pH treatments at where the coverage of metal hydroxide species obtained higher than that of chalcopyrite showing that the rate oxidation of tennantite is higher. An adsorption mechanism has been proposed and tested against the experimental kinetic data. Both the kinetic data and flotation studies are consistent with the proposed mechanism.     

Integrated optical digital-to-analogue converter and itsapplication to pulse pattern recognition

An optical digital-to-analogue converter that enables optical pulse pattern recognition, fabricated on the silica-based planar lightwave circuit, is proposed. The converter features an optical transversal filter with a multimode interference combiner. Various kinds of four-bit pulse patterns at 10 Gbit/s have been successfully recognised with the fabricated converter