Ultrashort pulse laser interaction with silica-silicon interfaces is presented as a means for all-solid-phase formation of high-purity silicon nanoparticles in the absence of ablation plumes or any substrate intermixing with surfaces in ambient air. Transmission electron microscopy and Raman spectroscopy provide definitive evidence for creation of nanocrystals in the silica host, while compressive stress in the silicon substrate corroborates the formation of optical waveguides parallel to the tracks.