Portable optical sensor using tunable optical multilayers

A functional portable optical sensor device using tunable nanostructured optical multilayers, its system description, properties and use for selected measurement purposes are presented. The portable optical sensor consists of an optical measurement unit including tunable nanostructured porous optical layers and a microprocessor controlled handheld instrument. The spectral information is provided by LEDs as light sources, the tunable optical multilayer in a closed measurement chamber, a photodetector and preamplifier. The basic sensor signal results from a spectral shift of the multilayer´s reflectance spectrum. This spectral shift is caused by of filling the porous silicon multilayer (PSML) with gaseous or liquid media which have to be analyzed. The sensor output spectrum is given as convolution of the used light source and the changing PSML reflectance spectra. The sensor sensitivity was investigated as function of the optical properties. Response times of the optical sensor were measured using different application conditions.