This highly interdisciplinary thesis reports on two innovative photonic biosensors that combine multiple simultaneous measurements to provide unique insights into the activity and structure of surface immobilized biological molecules. In addition, it presents a new silicon photonic biosensor that exploits two cascaded resonant sensors to provide two independent measurements of a biological layer immobilized on the surface. By combining these two measurements, it is possible to unambiguously quantify the density and thickness of the molecular layer; here, the approach's ability to study...