Sensitive Label-Free Biomolecular Detection Using Thin Silicon Waveguides

Figure 4

Schematic of the inversely tapered mode transformer used for improved fiber-to-waveguide coupling. The nominal 0.45 𝜇m wide photonic wire sensor waveguide is laterally tapered down to 0.15 𝜇m for adiabatic expansion of the waveguide mode near the device facet.