The measurements and calculations of monolayer and multilayer reflectance, made of porous silicon films, have been carried out. The multilayer component has been made of porous silicon layers that has refractive indices of nA=2.16 and nB= 1.55. The band structure of one dimensional photonic crystal has been calculated using the transfer
matrix method which consists of alternative layers of two dielectric materials A and B. As for the multi layers component which are consist of the periodical repetition of two layers of different refractive indices (nH and nL) which has an omnidirectional photonic
band gap (PBG), the width of which depends on the incidence medium and on the refractive index ratio nH/nL. In porous silicon, this ratio is limited by the material and fabrication characteristics. Theoretical and experimental study has been carried on the wide range of practical fabrication parameters for the formation of omnidirectional PBG.
A band width of 400 nm is corresponding to a reflectivity higher than 97% which is suitable for applications of omnidirectional PBG at wavelength 1550 nm.