Experiments in this laboratory and the Corning Glass Works laboratories have established that highly resolved patterns of refractive index gradients ranging from 0. 001 to 0. 01 can be produced by photolysis of organotin compounds physisorbed onto Corning''s code 7930 porous Vycor glass followed by thermal consolidation of the glass at 1200CC. Photolysis binds the metal compound to the glass and thermal activation removes the unreacted adsorbate and converts the photoproduct to a transparent metal oxide. The photochemical and thermal reactions leading to gradient index formation will be described and examples of the devices produced by this microphotolithographic technique will be displayed.