Mode Selection in Optimization Based on Analytical Analysis of Complex Coupled-Mode Equations for High Refractive-Index Sensing

A novel mode selection is proposed for the optimization of high refractive index sensor based on chiral fiber grating. A unique quasi-leaky mode is selected as an approximately equivalence to the continuous radiation modes to describe the power change in response of the change of the ambient refractive index in the coupled-mode analysis. An enhanced simulated sensitivity of 701.04 dB/RIU is obtained by selecting the unique mode working at the most sensitive coupling state.