Monolithically integrated optical interference and absorption filters on thin film amorphous silicon photosensors for biological detection

High selectivity of photosensors is needed for targeted biological detection. Optical interference filters are monolithically integrated with hydrogenated amorphous silicon thin film photosensors for fluorescence measurements in lab-on-chip applications using a methodology that enables customization of fluorescence detection for various applications. The design of the optical interference filters is tailored to match the requirements of each application and the filters are fabricated as nitride-oxide multilayers. The interference filters are combined with hydrogenated amorphous silicon-carbon alloys, which serve as long-pass absorption filters, depending on the spectral requirements. In this work we demonstrate the development of these filters, through simulations and design, followed by experimental fabrication and characterization of transmission spectra, and finally, integration with photosensors which are implemented in measurements to detect fluorescence in three different applications, including bacteriophage fluorescence, quantum dot and Cy3 fluorophores, and grape fluorescence for grape maturation monitoring, in a novel methodology that allows for simplification and greater portability of the measurement setup and negates the need to stack optical filters in fluorescence applications.