Optical properties of porous silicon.

By knowing the wavelength dependent optical parameters (refractive index n and absorption coefficient α) and the obtained thickness of porous silicon (PS) layers when anodizing boron-doped Si wafers, one can design and realize periodic structures by alternating the current density during anodization. Such periodicity in the structure––and thus in optical properties within a film––results in a superlattice, which acts as a Bragg grating. By considering the proper Bragg conditions, the fabrication of optical filter/reflector components can be performed in a simple manner. In this paper, both theoretical and experimental aspects of the fabrication procedure are investigated.