The silicon photonic platform is widely used for optical sensing and communications because its high index contrast allows for smaller devices, and is compatible with CMOS manufacturing techniques. In this thesis we examine theoretically and demonstrate experimentally silicon-on-insulator biochemical sensors based on micro-ring resonators (MRR) and ring assisted Mach-Zehnder interferometers (RAMZI). We determine that the sensitivity of the slot waveguide is enhanced compared to the wire waveguide and examine the effect of coupler design on sensing performance using directional couplers and multi mode interference (MMI) couplers. We find that RAMZI devices offer a similar sensitivity while offering a larger index of refraction measurement range than MRR designs. The slot waveguide is found to increase bulk index sensing sensitivity by up to 2.2 times that of the wire waveguide. Directional coupler based MRR and RAMZI devices are shown to have higher bulk index sensitivities than MMI coupled devices.