Aperiodic photonic bandgap devices based on nanostructured porous silicon

In this work, we have compared the optical characteristic of two different photonic dielectric multilayers based on the porous silicon technology. We designed and realized two models devices: a Bragg mirror and the S6 Thue-Morse sequence. Both the structures have the same thickness, the same porosity, and even the same number of the layers but differently spatially ordered. We demonstrate that the two arrangements of the layers influence not only the optical features of these interferometric devices but also their sensitivity when used as optical sensors. We have measured the change of the reflectivity spectra of the devices on exposure to several organic compounds. The experimental results demonstrated that the Thue-Morse aperiodic structure is more sensitive than the Bragg device due to a higher filling capability.