Optimization of the Local Evanescent Array-Coupled Optoelectronic Sensing Chip for Enhanced, Portable, Real-Time Sensing

Performance of the local evanescent array coupled (LEAC) biosensor is optimized by modifying the CMOS-compatible fabrication scheme and fine-tuning waveguide parameters based on simulation results of a full-vector finite difference mode solver. To enable in situ, real-time detection, an index-matched upper cladding reference region is patterned onto the waveguide. The reference region is followed by a sensing region exposed to the analyte, which is delivered via a flow cell. An on-chip, continuous photodetector array is implemented, which enables the fabrication of an optically smooth lower cladding/core interface, removing the need for chemical-mechanical polishing. As close mode-matching between reference and sensing regions increases the optical power launched into the sensing region, different mixtures of oils (n=1.4680-1.4722) were used as a proof of concept for real-time refractive index measurements. The ~ 1-cm² LEAC chip, which exploits three independent sensing mechanisms, is demonstrated to have a static sensitivity of 4.6×10^-6 RIU and a real-time (2s resolution) sensitivity of 4.1×10^-5 RIU.