Porous silicon lateral superlattices

Lateral superlattices in porous silicon layers have been generated. Using the photosensitivity of the etching process, periodic stripes are formed not only on the surface but also in the depth of the layer. The modulation depth depends on the illumination wavelength. The periodicity is obtained from the interference pattern of two laser beams, and can be easily modified by changing the wavelength or the incidence angles of the beams. The samples formed by this procedure were characterized by light diffraction. Two-dimensional structures can also be obtained by rotating the sample or by interference of four laser beams. This kind of in-depth lithography and the resulting low-cost fabrication of gratings out of porous silicon offer a wide range of potential applications in integrated optics and photonics.