The experimental results of Fig. 4 clearly prove that for homogeneous sensing experiments, it is more reasonable to perform the measurements with a weakly confinent resonant mode as is the case for the qTM mode, which has a stronger interaction with the analyte and consequently results in a higher sensitivity; in this case, the improvement is nearly a factor of 10. For surface sensing experiments, the main interaction of the evanscent field happens in a thin molecular layer sticked close to the sensor surface so that here a weak confinement does not necessarily improve the performance. For convenience to use the grating couplers (designed for qTE-mode) instead of cleaving the chip facets, the measurements were performed with the qTE-mode. The FEM simulations indicate that the qTM-mode would yield a 1.6 times lower detection limit. From the recent results, we suggest that a-Si:H is an attractive photonic material for lab-on-chip sensing applications, especially when combined with microfluidic channels supporting a well-defined analyte flow rate and if functionalized markers with receptors are employed which facilitate a selective detection of target molecules. The experiments show that a procedure of piranha etch, aminosilanization, and glutaraldehyde functionalization is process-compatible with low-loss amorphous silicon material, and the results from the optical characterization of a ring resonator with BSA protein adsorpted to the ring surface reveal that molecular masses down to the fg region or a surface coverage of can be detected for a conservative assumption of a 1-pm wavelength accuracy of the readout system. Further improvements are expected by a refinement of the waveguide cross-section, an improvement of the -factor by employing less strong absorbing buffer solutions and by an optimization of the resonator functionalization procedure.