In this work, we report on the fabrication of an hybrid material based on a porous silicon (PSi) layer infiltrated by an amino functionalized poly(ε-caprolattone) (PCL-NH2). The organic–inorganic structure has been characterized by variable angle spectroscopic ellipsometry, optical reflectometry and water contact angle measurements. A polymer coated PSi layer, 3 μm thick, shows improved wettability and chemical stability against long lasting, up to 18 min, exposure to an alkaline environment. Even after basic treatment, the structure still retains a very good quality optical response, so that it may be proposed as a high performance platform for biochemical sensing applications.