tion. For the other polarization and orientation combinations, no bandgap was observed. This result slightly contradicts the theoretical calculation made using the plane-wave method, where the appearance of a complete bandgap for H polarization is predicted, and also the latest photonic bandgap measurements made by Masuda and co-workers. [5, The absence of a dip for E polarization confirms that, for E polarization, porous alumina has a rather less expressed bandgap. Moreover, the theory concludes that no bandgap for E polarization exists in the C±J direction: Although dips are observed in the transmission spectra, [5, they can be assigned to the uncoupling of the second lowest band to an external electromagnetic wave in this direction. In support of our experimental observations, it should be mentioned that the relatively small refractive index contrast of about 1.7 in the aluminum AOF is considerably smaller than the commonly accepted minimum index contrast of 2.66, which is indispensable for a complete photonic bandgap in the triangular lattice with optimal filling fraction, and even more different from the traditional materials GaAs and Si. In summary, we have demonstrated a new, simple, and effective method of making anodic aluminum oxide films of almost unlimited size and with perfectly ordered structures of cells of sub-micrometer dimensions. Our method is highly reliable, due to the use of a commercial optical grating for the prepatterning of the surface. From our optical transmission measurements, we can confirm the existence of a photonic bandgap in the visible region, thus indicating that the prospects are good for use of this fabrication technique to make large structures, which are in turn useful for conventional spectroscopic applications and for two-dimensional photonic crystal development. Moreover, it creates the possibility of forming photonic crystals by using holographic optical lithography, commonly used for the production of diffraction gratings.