Abstract: The present invention discloses a method whereby laser microwriting is used to microanneal an amorphous silicon phase to a nanocrystalline silicon phase in silicon photonic crystals, films, fibers or surface patterns to enable the precise definition of a pre-determined refractive index contrast pattern in spatially designated regions of amorphous silicon photonic crystals, films, fibers or surface patterns in a rapid and straightforward fashion. At the micrometer length scale of the silicon photonic lattice the method can be used to create extrinsic defects in silicon photonic crystals, films, fibers or surface patterns, exemplified but not limited to points, lines and bends for localizing, guiding and bending light.