GeS2–Sb2S3–CsCl glass–ceramics with fine porous surfaces were synthesized and tested as optical elements. The porosity is obtained through a two-step process, including controlled nucleation of CsCl nuclei in the glass matrix followed by selective etching of the nuclei with an acid solution. The porous surface is several hundred nanometers thick and results in a surface area increase of almost four orders of magnitude. The pores size is approximately 150 nm and can be tailored by controlling the nucleation process and the etching time. It is shown that the creation of the porous surface does not critically affect the optical transmission of these infrared (IR) transparent glass–ceramics. These materials can therefore be used for the design of optical elements and an attenuated total reflexion plate with porous surface was fabricated and tested as an optical IR sensor. The porous element shows higher detection sensitivity in initial experiments with an analyte sprayed at the plate surface and a coating of silane molecules.