Integrated photometer with porous silicon interference filters

Porous silicon transmission interference filters with laterally varying transmission wavelengths are used to manufacture a photometer. Because of the linear varying transmission characteristic of the filter it is possible to measure, beyond small regions of the porous layer, the correlated spectral photo current. It is therefore necessary to bring up a series of ohmic metal contacts along the porous filter. Between two neighbouring contacts one can measure the spectral photo current of the transmission wavelength at this specific point of the surface. By measuring multiple pairs of contacts, the whole spectrum between 400 and 1100 nm wavelength can be recorded. First results of the resolution capability and sensitivity are demonstrated.