Gas sensing near exceptional points

Here we investigate the possibility of gas sensing with ultrahigh sensitivity by exploiting the exceptional point (EP) in a non-Hermitian system. The underlying mechanism is that the transverse displacement induced by the photonic spin Hall effect (PSHE), which is significantly enhanced near EPs, is ultra-sensitive to the variation of refractive index in gas media. With the application of the weak measurement technique, we find that the sensitivity of the gas sensing can reach ${10}^{-6}\text{RIU }\mu {\text{m}}^{-1}$. Moreover, if we further reduce the in-plane wavevector component of probe Gaussian light, the sensitivity can be readily improved, up to ${10}^{-8}\text{RIU }\mu {\text{m}}^{-1}$, which is much better than that of previous PSHE-based gas sensors operating away from the EP. Therefore, our proposed scheme may be favorable for the development of high-performance sensors. (paper)