Position-tracking-based GMR Detection Modality

This study presents a cost-effective approach to implement the guided mode resonance (GMR) sensors for refractive index (RI) measurements. A silicon nitride (Si3N4) GMR chip, fabricated using e-beam lithography and incorporating an in-house diffraction grating, is integrated with a low-cost CMOS sensor for optical readout. This system effectively detects variations in the GMR output corresponding to RI changes. Experimental results demonstrate a sensitivity of 2.02 mm RIU-1, derived from the linear regression slope of the CMOS intensity spot position against RI variations. This innovative combination of GMR and CMOS technologies not only reduces costs but also significantly simplifies the detection mechanism, opening new possibilities for optical sensing applications.