Design of an on-chip sensor operating near the dispersion turning point with ultrahigh sensitivity

Abstract

In this paper, an on-chip refractive index (RI) sensor based on the asymmetric Mach–Zehnder interferometer (MZI) is proposed for sensitivity enhancement. The outstanding sensing performance is obtained by achieving the dispersion turning point (DTP). We analyze the necessary conditions for DTP formation, the transmission spectrum characteristics, and the sensing performance near the DTP. The results show that when the group index difference between the reference arm and the sensing arm is close to zero, high RI sensitivity can be obtained near the DTP. Since the resonance peaks on both sides of the DTP have different shift directions with the change of RI, by tracing the wavelength shift between the two resonance peaks, the RI sensitivity and the limit of detection can reach 40960 nm/refractive index unit (RIU) and 4.88 × 10 − 7 R I U . The proposed asymmetric MZI sensor provides a potential on-chip platform for high-performance RI sensing.