PURPOSE: To provide the optical defractor which has stable quality and is easily integratable.

CONSTITUTION: This optical defractor is formed by using a porous silicon film 30 for an optical waveguide. The porous silicon has the characteristic that the light transmittance decrease when the intensity of input light is high and that the light transmittance increases when the intensity of the input light is small. The porous silicon film 30 is produced by using, for example, an anodic chemical conversion method. Interference of pumping light beams L1, L2 takes place within the porous silicon film 30 and bright and dark stripe patterns by absorption of light are formed when the pumping light beams L1, L2 are first made incident on the porous silicon film 30 of such optical defractor. An input beam L is diffracted by these stripe patterns when the light beam L is inputted to the porous silicon film 30.