Research On D-Shaped Photonic Crystal Fiber Sensor Based On Surface Plasmon Resonance

Optical fiber sensors have very wide application prospects and extremely significant academic research value.Based on the porous structure of photonic crystal fibers,the surface plasmon resonance effect generated by filling metal nanowire or coating metal film has become a research hotspot in the field of optical fiber sensors in recent years.In particular,the research on D-shaped photonic crystal fiber sensors combined plasmon excitation material is more noticeable.The D-shaped photonic crystal fiber sensor has a more significant advantage than a conventional plasmon resonance sensor,which performs metal filling or coating in the holes of photonic crystal fiber.Specifically in:(1)Compared with the filling or coating in the holes,the D-shaped photonic crystal fiber sensor only needs to be coated with gold film on the polishing surface,the preparation process is more mature,and the stability of preparation and uniformity of coating are better;(2)Due to the existence of the D-shaped structure,the original symmetry of the optical fiber is destroyed,the leakage of energy from the core mode to the optical evanescent field is controllable,and the sensitivity and loss intensity of the optical fiber are further enhanced,thereby greatly improving sensing capability of optical fiber;(3)The presence of the polished surface greatly enhance the connection between the sensor and the liquid to be tested,and greatly increases the perception of the refractive index change of the analyte,thereby making the performance of the sensor more stable.The content of this paper focuses on the frontiers of application requirements and related scientific and technological,and theoretically and experimentally conducted a series of research on D-shaped photonic crystal fiber sensor based on surface plasmon resonance.Firstly,a single-channel D-shaped photonic crystal fiber sensor is theoretically designed and simulated.The polished surface of the D-shaped fiber is provided with a groove coated with gold film,and serves as a sensing channel for the analysis liquid to be tested.The sensor not only has an ultra-wide refractive index detection range of 1.26-1.36,but also has high wavelength sensitivity,and also enable simultaneous detection of transmitted signals in the x and y polarization directions at different frequency bands.Secondly,a D-shaped photonic crystal fiber sensor with dual channels on the polished surface is proposed and studied.Unlike previous D-shaped fiber sensor,the sensor creatively coats a gold film on the plane between the two micro-openings,making the thickness of the gold film uniformity of coating more controllable.At the same time,the detection range of refractive index for the sensor can be from 1.31 to 1.37,and the corresponding maximum sensitivity can reach 11750nm/RIU.Finally,the optical fiber polishing experiment platform was creatively proposed and built,and a variety of photonic crystal fibers were polished by the platform.The specific experimental scheme and precautions for manufacturing D-shaped photonic crystal fiber were described.The silver film is coated on the polished surface of D-shaped photonic crystal fiber,thereby the surface plasmon resonance is introduced into the D-shaped photonic crystal fiber,and the experimental preparation of the fiber plasma sensor is realized.Then,the sensing characteristics of the sensor were measured by the detection system.The average wavelength sensitivity of the sensor was 842.6nm/RIU with the refractive index of analyte varying from 1.3415 to 1.3468.When the refractive index was 1.3490,the highest wavelength sensitivity reached 3973.8nm/RIU.The research in this paper has very important reference value and positive scientific significance for exploring new optical fiber sensing technology,which will also promote the development of metal-coated D-shaped photonic crystal fiber sensor.