Single-chip photo-spectrometers realized in standard complimentary-metal-oxide-semiconductor (CMOS) technology

Two photo-spectrometers have been realized using a standard integrated circuit (IC) process. One photo-spectrometer used only the masks, materials and fabrication steps inherent to the IC process (i.e. no post processing to add mechanical or optical devices for filtering). This spectrometer was composed of a set of 18 photodetectors with independent spectral responses. The second photo-spectrometer used a simple procedure to deposit a thin-film of amorphous Si on an array of CMOS photodiodes. The thickness of the amorphous Si coating varied in an approximately linear fashion across the array. In both cases, the responses of the photodiodes were weighted and summed to form outputs proportional to the input optical power in discrete wavelength bands in the region from approximately 400 nm to approximately 1100 nm. These devices could easily be integrated with additional analog, digital, or wireless circuits to realize true laboratory instruments on chips.