Multilayer structure for a spectral imaging sensor.

We investigate the possibility of recovering spectral information using a multilayer structure realized through microelectronics technologies and compatible with a matrix arrangement. The structure is made of photoabsorbing layers, acting as local photodetectors, alternating with transparent layers. The whole structure lies on a reflective surface. A stationary wave containing the spectral information of the source is generated within the structure. We determine the intensity of the stationary wave at any position, taking into account absorption and multireflections at each transition as well as the signal detected by the photoabsorbing layers. The model forecasting the detected signal is then validated using p-i-n diodes of different thicknesses made of hydrogenated amorphous silicon (a-Si:H) encompassed between indium tin oxide (ITO) electrodes. The detected signal depends on the wavelength of the incident light, the thickness of the detecting layer, and the latter's position within the structure. A specific spectral response can then be associated to each photoabsorbing layer. We show how spectral information can be retrieved from this kind of structure in the visible spectrum range.