Far-infrared dielectric constant of porous silicon layers measured by terahertz time-domain spectroscopy

We measure the refractive index and the absorption of porous silicon layers in the millimetric and submillimetric wavelength range using the terahertz time-domain spectroscopy technique. For the studied range of porosity (55%–76%), the refractive index of porous silicon is rather well described by mixture theories, in which the refractive index of bulk silicon enters as a main parameter.