Lateral superlattices in porous silicon layers have been generated. Us
ing 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 periodic
ity is obtained from the interference pattern of two laser beams, and
can be easily modified by changing the wavelength or the incidence ang
les of the beams. The samples formed by this procedure were characteri
zed by light diffraction, Two-dimensional structures can also be obtai
ned by rotating the sample or by interference of four laser beams. Thi
s kind of in-depth lithography and the resulting low-cost fabrication
of gratings out of porous silicon offer a wide range of potential appl
ications in integrated optics and photonics. (C) 1997 American Institu
te of Physics.