Abstract: A semiconductor laser comprises an optical wave guide layer including an AlGaInP active layer and AlGaInP optical confinement layers holding the active layer therebetween. A well structure of an energy band is formed and a compressive stress is applied to the activation layer by the difference between the compositions of the activation layer and the optical confinement layers. Since the compressive stress is applied to the activation layer, the oscillation threshold is lower than that of an un-strained device. Accordingly, the rise of the oscillation threshold due to the addition of Al is compensated and continuous oscillation at room temperature is attained and visible light having a wavelength of 0.67 .mu.m or lower, which has been difficult to attain in the past, is produced.

Abstract: An optical transmission fiber comprising (1) a core of high refractive index composed of SiO.sub.2 -based glass containing at least one of GeO.sub.2, As.sub.2 O.sub.3, Sb.sub.2 O.sub.5, SnO.sub.2, TiO.sub.2, PbO and Bi.sub.2 O.sub.3, (2) a clad of low refractive index composed of SiO.sub.2 -based glass containing at least one of F, F/B.sub.2 O.sub.3 and F/P.sub.2 O.sub.5, and (3) an outermost jacket layer composed of SiO.sub.2 and/or SiO.sub.2 -based glass containing at least one of Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2 and HfO.sub.2.

Abstract: An IC wafer with a uniform distribution of impurities is obtained by a pretreatment comprising annealing a semiconductor substrate at a high temperature for a long period of time and then cooling rapidly before IC processing.