With stacked silicon photodiodes and refined optical thin film filters, spectrally sensitive detectors can be developed that can replace conventional, expensive spectrometers needed for special applications. A further feature of such spectral sensors is the elimination of measurement errors caused by undesirable polarization of the radiating source when fiber-optical sensors are used.
The MEMS technologies at CiS were used for a new generation of spectral sensors consisting of two detector chips stacked on top of another, each covering a specific spectral range. The upper diode is only 50 µm thin.
The compact assembly of the detector chips including filters, beam shaping elements, fiber coupler as well as electronics and housing allows a minimum sensor size.
The new solution concept targets applications with a small wavelength range to be monitored. Narrow-band filters enable picometer accuracy. In addition, vibrations up to 1 MHz are measurable time-resolved with low noise.