Ultra-high sensitivity integrated photonic biosensors based on a feedback-coupled microring resonator

A high-performance sensor is crucial for the integration of optical biosensors, enabling the precise and rapid identification of target analytes. We present the correlation between feedback-coupled microring resonator (FBCMR) and variations in Mach-Zehnder interferometer (MZI) and microring resonator (MRR) phases. By introducing an asymmetric MZI into FBCMR, we have successfully achieved ultra-high sensitivity integrated photonic sensor whose refractive index sensitivity and limit of detection are 5752.5 nm/RIU and 1.6514 × 10-5, respectively. The photonic sensor is packaged with a PDMS microfluidic layer, forming an integrated optofluidic chip, which is applied to detect human alpha-fetoprotein (AFP). Such an integrated photonic sensor has no suspended or subwavelength grating (SWG) structure so that no need to challenge manufacturing processes which paves the way for application in high-resolution biochemical sensing and environmental monitoring.