Development of high sensitivity photonic sensing structures based on porous silicon substrates

Resumen

Health and well-being have always been the center of attention of many research institutions and companies around the world. This led the technology to develop in the chemical, biological, medical and clinical fields with the aim to provide a better protection to the human being. As a consequence, a competition is born between the time necessary to the disease to progress and the time necessary to man to treat such disease. In order to win this competition, it is necessary to act with anticipation, when disease is not too developed yet. This is possible by performing an early-detection. The achievement of this goal paves the way for the development of optical biosensing devices able to detect the presence of certain molecules at extremely low concentrations. Among them, photonic integrated structures are finding a great success due to their considerably high sensitivity. However, the sensing mechanism of these structures is based on the interaction between the evanescent wave, propagating along the structure surface, and the target analyte to detect. In this way, not all the field propagating in the photonic structure is used for sensing purposes, but rather only a small amount of it. This represents a crucial limitation of the integrated photonics based sensors. The aim of this PhD Thesis is to overcome this limitation and to develop more sensitive photonic sensing structures able to detect the lowest concentration possible. To this aim, we focused on the study of porous silicon as platform for the development of optical structures with extremely high sensitivities thanks to the fact that the sensing interaction takes place directly inside the structure itself, allowing to exploit all the field propagating in the structure.