Devices are described in which certain crosslinked silicone polymers are incorporated. These polymers have various functions such as encapsulating agents, surface protective agents or agents to index match optical components (e.g. optical fiber, optical waveguide, etc.) to other optical devices or articles. The polymer is a vinyl-terminated dimethyldiphenylsiloxane copolymer crosslinked with tri- or tetrafunctional silanes in the presence of a platinum catalyst. The phenyl group content of the crosslinked silicone copolymer is adjusted to change the index of refraction of the polymer to the optimum for the particular application contemplated. Polymer preparation procedures are described which yield good optical quality for the polymer as well as optimum physical and chemical properties.