Polarization-Dependent Tuning Property of Graphene Integrated Tilted Fiber Bragg Grating for Sensitivity Optimization: A Numerical Study

In this paper, the general characteristics of the polarization-dependent tuning property and sensitivity optimization of the graphene integrated tilted fiber Bragg grating (TFBG) are investigated theoretically. The tuning mechanism of the graphene on mode characteristics and transmission spectrum is thoroughly explored. The results reveal that the graphene induces a stronger influence on the s-polarized mode than its p-polarized counterpart, but the TFBGs with or without graphene in all the polarized states have nearly the same wavelength sensitivity ( $\sim \text{540}\; \text{nm/RIU}$ in average). In contrast, the resonance strength is highly dependent on the tunable state of the graphene, especially for the s-polarized case. In consequence, the normalized power response is increased in the low refractive index region. More importantly, the s-polarized leaky mode resonance that is ignored for regular TFBGs is significantly enhanced (by increasing field content in the fiber region and decreasing the confinement loss) whereas the guided counterpart is suppressed greatly by the graphene with lower chemical potential. The sensitivity of up to $ \text{6595.8 dB/RIU}$ (9.17 times higher than that of the regular counterpart) is achieved in response to an extremely small analyte perturbation ( $ \text{10}^{-\text{4}}$ close to 1.333) based on the graphene enhanced leaky mode resonance. This paper provides a novel technique for significantly optimizing the sensing performance of the TFBG, which has great potential in biological and biochemical sensing applications.