ABSTRACT
Gold line-and-space (L/S) surface plasmon antenna is introduced to enhance the sensitivity of silicon-on-insulator photodiode (PD), which also realizes sensitive refractive index (RI) measurement of the medium around the antenna, providing a new opportunity in optical biosensing for unlabeled analytes. Unlike the conventional device such as the surface plasmon resonance (SPR) sensor, it has a built-in photodetector, features a small footprint, and can be integrated in large numbers for high-throughput analysis. A chip and a flow system compatible with aqueous solutions are fabricated and tested with sucrose solutions. Thanks to the twoPD configuration with different L/S periods, a minimum detectable RI of 1.11×10–5 is attained, which is comparable to that of the SPR sensor. Furthermore, the change in the quantum efficiency of the PD with respect to the thickness of the analyte covering the Au line is simulated, and it is found that a few-nanometer-thick analyte such as avidin-biotin complex could be detected.
