Increasing sensor sensitivity and maintaining a large FOM (figure of merit) are challenging to achieve at the same time. Adding grooves and asymmetrical structures to the annular cavity increases sensitivity; however, it usually makes the FOM of the structure decrease. Herein, we propose a MIM (metal-insulator-metal) sensor of a novel structure with nano-cylinders loaded in a ring resonator (NCRR), whose sensitivity can reach as high as 3636.4 nm/RIU (refractive index unit). The FOM is maintained around 2000 in the mid-infrared (MIR) region. We find that grating effects only occur in the ring cavity when the cylinder’s distance is below three times its radius, and it can improve the sensitivity of the proposed structure up to 42.3% without decreasing its FOM. In addition, results suggest that our sensor has excellent resistance to eccentricity, which brings in manufacturing. Furthermore, we investigate the capability of the proposed device as a temperature sensor with ethanol, which exhibits a maximum temperature sensitivity of 1.48 nm/∘C. We believe that our research has essential application prospects in miniature integrated sensors, optical switches, splitters, filters, and broadband passers.

Optical vortices (OVs) carry the orbital angular momentum with arbitrary topological charges, which has excellent potential in optical communication, photonic integrated circuits, optical trapping, and so on. However, it remains to be solved generating arbitrary orders of adjustable optical vortices. Here, we propose a single-layer metal porous metasurface operating in infrared band for generating vortex beams from first to fourth order based on the spin-orbit interactions (SOI). The optical vortices with integral 2π phase are obtained through generating double geometric phase induced by structural element spin rotation. Further more, the new phenomenon of optical vortices emerging on the center has also been observed in our system, which is caused by the coupling of multi-channel same-order OVs. Our works possess wide applications in optical communication, multiplex and demultiplex systems, optical capture devices, and communication coding.

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