We present a theoretical and experimental study on the effect of progressive porosity increase, through multiple oxidation/oxide removal steps, upon the optical characteristics in threedimensional macroporous silicon. It is shown that, by increasing porosity, optical features can be pushed toward higher frequencies. Optimum porosities exist where normal or omnidirectional total reflection bandwidths are maximized, doubling the initial values. Results are confirmed experimentally through angle-resolved reflectance and thermal emission measurements.

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