Abstract: A three-dimensional structure of porous silicon considerably improves the anchorage of sensor-active material such as, for example, enzymes, antibodies, etc., on or in the substrate surface of chemical sensors, in particular silicon-based biosensors. This structure is produced by means of suitable etching which forms pore apertures adapted to the penetrability of the sensor-active material. The pore walls advantageously receive a non-conductive boundary layer which consists of oxides of Si and/or Al or Ta or silicon nitride and are preferably 1-100 nm thick. The porous layer is advantageously between 10 nm and 100 .mu.m thick and the pores are preferably in the form of branched ducts whose average diameter is 1 nm-10 .mu.m and in particular 10-1000 nm. The sensor-active material can optionally be distributed in a glass, solid, plastics or polymer membrane.

Abstract: The invention relates to an optical component consisting of transparent thin layers of differing thickness and refractive indices. Such optical components are used, for example, as interference filters and mirrors. Optical components made of layers with gradually changing refractive indices are also known as waveguides of anti-reflective coatings. The invention achieves the aim of using, instead of layers of ordinary materials, another material by means of a component in which the layers consist of porous silicon. The special advantages of porous silicon as a coating material arises not only from the ease and economy of manufacture, but also in the facility for obtaining gradual refractive index transitions. It is therefore very easily possible to make waveguides on a silicon chip.