Optical waveguide, forming material and making method

An optical waveguide formed from an optical waveguide-forming material, said optical waveguide-forming material comprising a photocurable organopolysiloxane composition comprising an alkali-soluble organopolysiloxane and a photoacid generator,

• said organopolysiloxane possessing hydroxyl groups resulting from ring-opening of some or all of epoxides, and being obtained by (co)hydrolytic condensation of at least one silane compound having the formula (1):
• R1Si(OR2)3 (1)
• wherein R1 is a monovalent organo group of 2 to 30 carbon atoms having hydrolyzable epoxide, and R2 is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, and having an average molecular weight of 500 to 50,000 as determined by GPC using polystyrene standards,
• wherein said (co)hydrolytic condensation comprises carrying out (co)hydrolysis in the presence of an acid catalyst, thereby forming a (co)hydrolyzate, and then subjecting the (co)hydrolyzate to polycondensation, while alcohol formed and any solvent present is distilled off by heating, thereby yielding a (co)hydrolytic condensate having silanol groups.