Abstract: A distributed feedback semiconductor laser which has, in an active layer or an adjoining layer, first corrugations causing periodic refractive index variations in the travelling direction of light and performs laser oscillation by the injection of a current into said active layer portion. In accordance with the present invention, second corrugations are formed to be aligned obliquely to said first corrugations, thereby causing additional loss to the TM mode to permit oscillation in the TE mode alone.

Abstract: A process for the solvent deasphalting of asphaltene-containing hydrocarbons which comprising mixing asphaltene-containing hydrocarbons with a metal compound such as aluminum sulfate or titanium (IV) oxide and also with a solvent such as n-heptane, n-hexane, n-heptane or a mixed n-pentane.n-butanol solvent, to form a mixture which is then allowed to stand still to precipitate and separate the asphaltene therefrom thereby obtaining a deasphalted oil.

Abstract: A distributed feedback semiconductor laser which is characterized in that periodic corrugations are performed in the surface of an InGaAsP quaternary layer so that an InP layer is grown thereon so as to overcome difficulties in prior arts.

Abstract: A continuous process for solvent deasphalting asphaltene-containing hydrocarbons which comprises mixing (A) 100 parts by weight of asphaltene-containing hydrocarbons with (B) 0.005-0.5 parts by weight of an amorphous silicon dioxide and/or a silicate compound and also with (C) 5-2000 parts by weight of a solvent such as n-heptane, n-hexane, n-heptane or a mixed n-pentane.n-butanol solvent, to form a mixture which is then allowed to stand still to precipitate and separate the asphaltene therefrom thereby obtaining a deasphalted oil.

Abstract: An avalanche photo diode provided with a guard ring around a photo detecting region having a pn junction, in which semiconductor layers of the photo detecting region having a pn junction, different in conductivity type from a semiconductor of the guard ring, are composed of a second semiconductor layer formed in contact with a first semiconductor layer forming the pn junction of the photo detecting region and of the same conductivity type as the semiconductor of the guard ring, and a third semiconductor layer formed in contact with the second semiconductor layer and having a larger band gap than the second semiconductor layer, and in which the tip end of the guard ring is formed to extend down into the third semiconductor layer.

Abstract: A semiconductor laser formed on an InP substrate to have a hetero structure comprising a plurality of In.sub.1-x Ga.sub.x`As.sub.y P.sub.1-y (0.42y.ltoreq.x.ltoreq.0.5y,0.ltoreq.y.ltoreq.1) layers which are lattice-matched with InP, in which a light emitting layer included in the layers and having a forbidden band width larger than 0.6 eV but smaller than 0.9 eV at room temperature is sandwiched between two InP layers on the InP substrate, and in which there is provided between the light emitting layer and the InP layer grown thereon at least one buffer layer having a forbidden band width larger than the forbidden band width of the light emitting layer but smaller than the forbidden band width of InP. The forbidden band width of the buffer layer at room temperature may be larger than 0.8 eV but smaller than 1.0 eV.

Abstract: An avalanche photodiode with a semiconductor hetero structure, in which a light absorbing region and an avalanche multiplying region where avalanche gain is attained are formed of different materials. The different materials may be two compound semiconductors of different compositions. The lattice constants of the two compound semiconductors may be matched with each other.

Abstract: A method for producing III-V compound semiconductor crystals using a liquid phase epitaxial growth, in which the crystal growth is achieved in a state in which a single crystal of the same composition as a single crystal serving as a substrate for crystal precipitation is present in a melt for the liquid growth.