Abstract: A parallel optical switching apparatus wherein at least one m-channel light emission element array and one n-channel light receiving element array are optically connected via an m.times.n optical conversion element array and the optical conversion element array has an optical amplification function by inductive discharge of input light for each element and performs optical arithmetic or optical conversion in parallel for input light from the light emission element array by the amplification and modulation function.

Abstract: A method of removing scale in a cooling water system in which scale is formed comprises adding 0.01 weight % or more based on the total amount of water contained in the cooling water system of a copolymer containing vinyl monomer units having a carboxyl group or salt thereof and vinyl monomer units having a sulfo group or salt thereof in amounts to make the mol ratio of the carboxyl group to the sulfo group in the range of 30:70 to 95:5 and having weight average molecular weight calibrated with polystyrene in the range of 1,000 to 100,000 to the cooling water system while operating the cooling water system and the cleaved or dissolved scale is discharged out of the cooling water system by blowing.

Abstract: A semiconductor laser device including at least one of a laser active layer formed of a super lattice and an optical guide layer formed of another super lattice is disclosed in which part of at least one of the super lattices is converted into a mixed crystal by the impurity induced disordering based upon one of impurity diffusion and impurity ion implantation, to divide the super lattice into a first region formed of the mixed crystal and a second region having the super lattice structure, the width of the second region in directions perpendicular to the lengthwise direction of a laser cavity varies along the above lengthwise direction, and the width of a laser excitation region is smaller than the mean value of the width of the second region, to generate laser oscillation having a single transverse mode and a multi longitudinal mode. Thus, the semiconductor laser device emits a laser beam which is small in astigmatism and low in optical feedback noise.