Graphene Enhanced Leaky Mode Resonance in Tilted Fiber Bragg Grating: A New Opportunity for Highly Sensitive Fiber Optic Sensor

Tilted fiber Bragg grating (TFBG) presents many unique spectral characteristics for sensing. The widespread approaches to date are based on the cut-off mode resonance and surface plasmon resonance (SPR), whereas the leaky mode resonance is ignored in the literature. Herein, we theoretically demonstrate that the s-polarized (or TE/HE) leaky mode resonance (and the guided mode resonance) can be efficiently enhanced (and suppressed) by integrating graphene on the TFBG for a highly sensitive sensor. In contrast, the p-polarized (or TM/EH) mode (both leaky mode and guided counterpart) presents slight variation. The enhancement principle is discussed based on the variation in the mode characteristics induced by the graphene. The results show that the graphene enhanced leaky mode resonance presents ultra-sensitive intensity response but insensitive wavelength response to the extremely small analyte perturbation. The sensitivities are achieved up to 14108dB/RIU and 5232.6dB/RIU for the first two leaky modes in gaseous media respectively, which are 121 and 13 times higher than that of bare TFBG. This novel sensing platform provides a promising technique that can compete with the widespread SPR approach in fiber optic sensing fields, which opens up new opportunities for industrial, environmental, and biochemical sensing applications.