<p>An all-optical refractive index sensor based on a combination of a photonic crystal resonator and plasmonic rods is proposed in this article. The proposed structure is simulated using the finite difference time domain (FDTD) method with perfectly matched layers (PML) as the boundary condition. The proposed structure has a resonant mode at 1600 nm. The simulation results show that the proposed structure is sensitive to the radius and refractive index variation of different parts of the structure. The normalized transmission of the proposed sensor structure is more than 90%, and the bandwidth and the quality factor are 0.8 nm and 2000, respectively. Also, the sensitivity of the proposed sensor structure is related to the refractive index of the cavity simulated, and according to the results, the maximum amount of it is 445 nm RIU⁻¹, and the minimum is 344 nm RIU⁻¹. Thus, by optimizing the refractive indices of the cavity, the device’s sensitivity reaches a maximum level of around 445 nm RIU⁻¹. Finally, the dependence of the sensor behavior, such as sensitivity on the other physical parameters, such as the radius of photonic crystal rods of the proposed structure studied and a blue shift toward higher wavelengths, happened by increasing the radius amounts.</p>