The photobleaching process of poly-3butoxyl-carbonyl-methyl-urethane (poly-3BCMU) waveguides by means of an UV lamp and the 488-nm line of an Ar laser is characterized and modeled. The limits of the theory are discussed in light of experimental results, and we stress the role of the oxygen diffusion rate on the process. Finally, we adopt the photobleaching method to pattern a guided-wave micro-optic device and holographic diffraction gratings on spun poly-3BCMU films.