Curable silicone composition, cured product thereof, and optical semiconductor device

A curable silicone composition comprising:

• (A) 100 parts by weight of a linear organopolysiloxane having at least two silicon atom-bonded alkenyl groups per molecule, wherein at least 5 mole % of all silicon atom-bonded organic groups are aryl groups;
• (B) 1 to 100 parts by weight of an organopolysiloxane containing siloxane units represented by the general formula R13SiO1/2 where each R1 represents an independently selected monovalent hydrocarbon group, and siloxane units represented by the general formula SiO4/2, wherein the amount of alkenyl groups is at least 6% by weight;
• (C) an organopolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, in an amount that the silicon atom-bonded hydrogen atoms in the component is 0.1 to 10 moles with regard to 1 mole of the total alkenyl groups included in components (A) and (B);
• and
• (D) a hydrosilylation reaction catalyst, in an amount that promotes curing of the composition.