Near-infrared transmissive properties of porous Si/Al2O3 photonic crystal band gaps

The light transmission properties through one-dimensional (1D) photonic crystal (PhC) with known material porosity rather than refractive index (RI) was investigated at normal incidence. The 1D PhC consists of a periodic structure of porous silicon/porous alumina (PSi/PAl2O3) layers with different dielectric constants arranged in the same dimension. The transmission spectral was computed using the transfer matrix method (TMM) for isotropic materials. This was used to investigate the effect of porosity on the transmission bands through such structures in the near-infrared wavelength range of 800-2200 nm. The results revealed that increasing porosity, which cor-responds to a decrease in effective refraction index (ERI), narrows the transmission passband (PB). While the appearance of the stopband (SB) becomes more visible as porosity increases. Furthermore, the increase in unit cells resulted in the apparent formation of a transmission SB. Therefore, the transmission characteristics through porous materials-based PhC can be improved by controlling the porosity of the materials used as layers in such a design. These new insights on the porous materials-based PhC might inspire potential application such as se-lective filter in thermophotovoltaic systems.