Research On Gas Sensor Detection Method Based On Photonic Crystal Slow Light Structure

Photonic Band Gap Photonic Crystal Fiber(PBG-PCF),owing to its distinctive stomatal structure as an absorption chamber,has become a research hotspot in the field of optical fiber sensing.At the same time,the introduction of slow light effect in band gap fiber provides a new direction for trace gas detection.Combining optical fluid filling and gas-sensitive film coating,proposes a gas sensor based on hollow core photonic crystal fiber slow light for achieving accurate detection of methane gas concentration.The main research contents of the paper are as follows:(1)The slow light characteristics in the PBG-PCF structure are investigated theoretically.The effects of the air hole radius,position,and filling material on the slot waveguide dispersion curve and group velocity curve are studied in conjunction with Plane Wave Expansion Method,and the application of slow light factor in the field of gas sensing are analyzed emphatically.(2)The photonic crystal waveguide is used as the sensing structure,different gas-sensitive materials are introduced in the two channels,and the influence of the gas concentration on the transmission spectrum is analyzed using the finite-difference timedomain method.The optimized structure makes the two channels relatively independent,so as to achieve simultaneous measurement of hydrogen and methane gas concentration.(3)The hollow core photonic crystal fiber(HC-PCF)with octagonal cladding structure was selected as the sensing gas cell to explore the influence of filled light fluid on limiting loss and relative sensitivity,and its relative sensitivity was more than 65%,which proved the advantages of hollow core fiber in gas sensing.Then based on HCPCF slow light,a new gas sensing device is designed.The cladding air holes are filled with optical fluid and the absorption enhancement factor spectrum is tuned to the infrared absorption spectrum of the gas to be measured to quickly distinguish the type of gas.At the same time,the coating technique is introduced into the partial holes for methane concentration measurement.The results indicate that the sensitivity is 0.794 nm /% and the linearity in 99.978%,providing a new idea for high-sensitivity trace gas detection.The paper has 37 pictures,3 tables,and 97 references.