Abstract: Metamaterials, due to their unique subwavelength structural design and distinctive electromagnetic response characteristics, hold great promise in enhancing the sensitivity of surface plasmon resonance (SPR) sensors. In view of this, a D-type fiber SPR metamaterial sensor modified with a metallic nano-grating structure is designed in this work, and its sensing performance for low-refractive-index sensing detection in the range of 1.332–1.344 is evaluated. Firstly, based on the optical wave vector characteristics of evanescent waves and surface plasmon polaritons (SPPs), a theoretical analysis of theD-type fiber SPR sensor is conducted, and the analytical solution curves of resonance wavelength versus incident angle for different refractive indices are plotted, in order to study the conditions for SPR excitation under different propagation modes in the fiber. And then, a two-dimensional simulation model of the D-type fiber SPR metamaterial sensor is established for mode analysis, calculation of mode loss, and investigation of the sensor's sensitivity performance. Finally, based on the aforementioned simulation model, we construct sensor simulation models with different grating elements, such as single strips or double strips with different intervals, as well as sensor models using silver/copper instead of gold as the continuous metal layer and grating material, and make contrastive analysis of their sensitivity performances. The results show that changing the strip intervals of the double strip grating unit has little effect on sensitivity, which is almost consistent with the sensitivity of the sensor with single strip grating unit. And when silver is used instead of gold as the continuous metal layer material, the sensitivity performance of the sensor is optimal, reaching 1800 nm⋅RIU−1 .

Key words: surface plasmon resonance, sensitivity optimization, metal nano-gratings, D-type fiber