We report an experimental study of porous silicon-based rugate filters. Possible optimisations that can improve different features of the filters are investigated. We demonstrate sidelobe attenuation by means of half-apodization of the structures with a sinusoidal window. Reduction of interference ripples are experimentally observed through the insertion of index-matching layers on the boundaries of the structure. The superposition of two different designs to obtain a multi-stop-band filter is also demonstrated. We show the possibility of controlling the bandwidth of the stop-bands by varying the index contrast. All the results are discussed and compared with numerical calculations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)