We proposed a narrowband perfect absorber that was based on dielectric-metal metasurface for wide-band surface-enhanced infrared sensing. It is found that the narrowband perfect absorber can generate the hybrid guided modes with high quality-factor at infrared frequencies, which make the absorber highly sensitive to the surrounded analyte. Moreover, tuning the incident angle can actively modulate the resonant wavelength of absorber. Such an absorber with excellent features is employed to realize both refractive index sensing and infrared vibrational fingerprint sensing on a single substrate. It is demonstrated that a refractive index sensitivity of 1800 nm/RIU and figure of merit of 62 RIU⁻¹ can be obtained as the refractive index sensor. While, as a surface enhanced infrared absorption spectroscopy substrate, two closed vibrational modes of analyte with nanometer thick layers can be effectively identified and selectively detected with 50-folds enhancement by actively tuning the incident angle without any change in the structural parameters (periodicity, width, height, and refractive index of the grating) of the device after fabricating. Our study offers a promising approach for designing high-performance surface-enhanced infrared optical sensors in the infrared region.

A novel two-dimensional (2D) positioning method based on Raman distributed temperature sensing (RDTS) has been reported to dramatically improve positioning accuracy. Using a well-designed 2D distribution of optical fiber and corresponding algorithms, the heat source can be accurately located without crosstalk; however, there is a tradeoff between sensing distance and positioning accuracy. In our experiments, an RDTS system with a spatial resolution of 0.8 m along a 3 km multimode fiber (MMF) is used with specific 2D routing rules and corresponding algorithms. A positioning accuracy of about 0.1 m is obtained without hardware modification, which could be improved through the dense arrangement of fiber; however, this would sacrifice the sensing length. This solution can be used for both flat surfaces and curved surfaces such as pipes or tank surfaces. This scheme can also be extended to three-dimensional positioning using a delicate routing design of sensing fiber.