Abstract: A mount for a light emitting device, which includes a first silicon substrate provided with first holding grooves of trapezoidal cross-section for mounting optical parts arranged in the vicinity of the light emitting plane of a light emitting element and a positioning groove for the light emitting element on the surface thereof, a second silicon substrate provided with second holding grooves having a trapezoidal cross-section similar to that of the first grooves for holding the optical parts and a hole portion for inserting the light emitting element, and a covering member for air tightly covering the hole portion, whereby the optical parts and the light emitting element of the light emitting device are tightly sealed by the above-stated means. The first and second holding grooves have the silicon crystal plane of (111) as both the side surfaces of their trapezoidal cross sections, and extend in the silicon crystal orientation of <110>.

Abstract: A semiconductor laser having a structure such that a narrow strip mesa is formed above a laser active layer in a hetero-structure crystal so that it can generate a laser beam of improved optical property.

Abstract: Ethylene copolymer compositions having excellent dielectric properties comprising an alkylfluoranthene having the following formula: ##SPC1##(wherein R represents an alkyl group containing from 1 to 4 carbon atoms, and x is an integer of from 1 to 4, and when x is an integer of 2 or greater, R may be different or the same) in an amount of at least 0.5 parts by weight per 100 parts by weight of an ethylene copolymer.

Abstract: Polyolefin compositions having excellent dielectric properties comprising an alkylpyrene having the following formula ##SPC1##(wherein R represents an alkyl group containing from 1 to 4 carbon atoms, and x is an integer of from 1 to 4, and when x is an integer of 2 or greater, R may be different or the same) in an amount of at last 0.5 parts by weight per 100 parts by weight of a polyolefin.