Disclosed is a process for preparing a polyorganosilane which comprises subjecting a disilane compound having at least two substituted or unsubstituted hydrocarbyloxy groups in one molecule to disproportionation reaction in the presence of a catalyst comprising a reaction product of an organic alkali metal compound represented by the formula (I): wherein R represents a substituted or unsubstituted monovalent hydrocarbon group; and M represents an alkali metal, represented by the formula (III): wherein R.sup.3 represents a saturated or unsaturated chain or cyclic divalent hydrocarbon group or a divalent heterocyclic group, two or more R.sup.3 s may be the same or different and an ether oxygen atom may exist between two or more R.sup.3 s; p represents an integer of 1 or more; and M represents an alkali metal atom, and at least one of a disilane compound and a silane compound both of which have a substituted or unsubstituted hydrocarbyloxy group(s).
A polysilane optical device comprising a hydrocarbyloxy group-containing polysilane encapsulated with a material having a light transmitting property and air impermeability, such as a glass, a polystyrene, an acryl resin, or a polycarbonate. The optical device has a high durability, and optical characteristics and functions thereof do not greatly change.
In a polymer waveguide comprising a cladding layer with a low refractive index and a core layer with a high refractive index of a substantially rectangular section covered with the cladding layer, the core layer and a side cladding layer constituting the cladding layer in its portion located on both sides of the core layer are formed of a material comprising a branched polysilane compound containing a silicone compound. By virtue of this constitution, the polymer waveguide has a low loss and causes no significant change in optical characteristics upon a change in ambient temperature.
