Staggered Padé wavelength distribution for multi-Bragg photonic mirrors

• Optimized method to design and produce high reactive broadband multilayered mirror.
• Complex refractive index of porous silicon is used in transfer matrix calculation.
• Comparison between our experimental and theoretical spectra shows a good agreement.
• The presented method could be used to fabricate dielectric mirror with other materials.

High reflective mirrors are commonly used in solar concentration devices. It has been shown that photonic mirrors are suitable for this purpose. However, despite their high reflectivity, they absorb radiation and heat up showing degradation. To overcome this problem here we propose to enhance the reflectivity of the mirrors. We report an improved and easy method to design broadband high reflective mirrors and build them from porous silicon multilayers. Those are composed of a continuous arrangement of submirrors reflecting each one at a given wavelength. This method consists in staggering the wavelength distribution following a relation based on the Padé approximant. We simulate the reflectance spectra using the transfer matrix method taking into account the experimental complex refractive index of porous silicon. The comparison between the experimental and the reflectance spectra shows a good agreement. With this technique we have fabricated high quality dielectric mirrors that can be used for concentrated solar energy applications among others.