Highly sensitive recognition element based on birefringent porous silicon layers

Anisotropically nanostructured silicon layers exhibit a strong in-plane bir efringence. Their optical anisotropy parameters are found to be extremely s ensitive to the presence of dielectric substances inside of the pores. Pola rization-resolved transmittance measurements provide an extremely sensitive tool to analyze the adsorption of various atoms and molecules in negligibl e quantities. A variation of the transmitted linearly polarized light inten sity up to two orders of magnitude combined with a fast optical response in the range of seconds make these layers a good candidate for sensor applica tions. (C) 2001 American Institute of Physics.