Simulation of Reflectance of Porous Thin-Layer Systems

An important class of optical devices consists of multiple thin layers of porous materials such as silicon. After producing samples, one often has limited optical data, for example, reflectance spectrum and under this limitation one must fit the data to specific optical models in order to obtain the complete optical functions. This process may lead to unphysical fits if supplementary knowledge of the reflectance signal is not applied. For this reason, the simulation and modelling of the optical properties of this type of structures is an important tool for the design of optical devices. In this paper we use simulations to identify some key aspects of how reflectance is affected by different physical parameters that are carried by commonly used models in order to provide a basic guideline for analyzing and fitting the reflectance signal. We demonstrate some general trends for the reflectance of porous systems under low porosity and high porosity regimes analyzing its dependence on layer-thickness, energy gap and surface roughness. We emphasize trends that are independent of which model is used to represent the porosity.