COSAH - Research project

The COSAH project proposes to demonstrate the optical function of a biosensor device, using a diffraction grating associated with a thin film with a very high refractive index (n>3) such as hydrogenated amorphous silicon (a -Si:H) transparent to the used wavelength (NIR), which will allow in this configuration interrogation from the rear face of the transducer. The proposed approach is based on the exploitation of the unique phenomenon known as optical switch patented in 2017, already demonstrated in the case of a metallic grating (in reflection). The exploitation of the optical signal provided by orders 0 and -1 constitutes the basis of the sensor. These signals can have the same intensity for a certain angle of incidence and in the presence of a measurand (chemical, biological species), their variation is linearly opposite. The simple acquisition of the difference signal provided by the two detectors therefore constitutes an information on the index variations at the transducer surface and therefore reveals the presence of the species to be detected. This project will then make it possible to validate with a demonstrator, a proof of concept of an optical sensor using a resonant grating (Hubert Curien Laboratory) associated with a layer of a-Si:H (HEF/IREIS).