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Photonic crystals containing the rugate structure result in a mirror with high reflectivity in a specific narrow spectral region and are prepared by applying a computer-generated pseudo-sinusoidal current waveform. Strategies to encode multiple rugate structures have been investigated. Multiple rugate structures can be etched on a silicon wafer and placed in the same physical location, showing that many sharp spectral lines can be obtained in the optical reflectivity spectrum. The method used to generate multiple rugate structures containing all the encoding information displays five rugate peaks corresponding to each of the sine components from 0.16 to 0.24 Hz, with a spacing of 0.02 Hz between each sine component. The complete deletion of a peak has been achieved and demonstrates the capacity of this method to create binary codes. The free-standing rugate porous silicon has been treated with the solution PMMA to produce composite materials which are highly flexible at room temperature. They display significantly improved mechanical stability and no apparent degradation in their optical reflectivity properties upon flexing. The spectral feature is shifted to longer wavelengths, indicating that the polymer has infiltrated the pores of the porous silicon matrix. The composites are stable in aqueous HF or alkaline (3 M KOH) solutions for several days without apparent degradation.